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THE SPATIAL AND TEMPORAL DISTRIBUTION OF TABANID
(CHRYSOPS, HYBOMITRA AND TABANUS) SPECIES IN THE NAKINA
DISTRICT OF NORTHWESTERN ONTARIO
A Thesis Submitted to the Committee on Graduate Studies in Partial Fulfillment of the
Requirements for the Degree of Master of Science in the Faculty of Arts and Science
TRENT UNIVERSITY
Peterborough, Ontario, Canada
(c) Copyright by Janette Fabiana Buckley 2018
Environmental and Life Sciences M.Sc. Graduate Program
January 2019
ii
ABSTRACT
The spatial and temporal distribution of tabanid (Chrysops, Hybomitra and
Tabanus) species in the Nakina district of northwestern Ontario
Janette Fabiana Buckley
This thesis focused on expanding knowledge of Hybomitra, Chrysops and
Tabanus (Diptera: Tabanidae) distributions north of Lake Nipigon, Ontario, in a
managed boreal forest. As land use and climate changes accelerate, there is increased
pressure to increase knowledge from which to monitor changes. In 2011 and 2012,
8928 individuals representing, 44 species were captured using sweep netting. Major
northward range extensions were observed for Chrysops shermani, C. aberrans and
Tabanus fairchildi. Smaller range extensions and in-fills were observed for another 15
species. 23 species had exntensions to their previously known seasonal range. C.
carbonarius was the only species that showed an extension to both sides of its season.
In general, harvested stands had 50% more individuals and 30% greater species
richness than younger stands. A possible link between stand age and interspecific
competition was identified. Information has been provided to build baseline of species
richness, relative abundance and distribution of Tabanid flies.
Keywords: tabanid, horse fly, deer fly, northern Ontario, natural history, species
range, habitat, seasonal distribution, Ontario, diptera, Chrysops, Hybomitra,
Tabanus
iii
Acknowledgements
I want to thank my supervisor David Beresford for his constant support,
guidance and encouragement.I would also like to thank my committee members,
Erica Nol and Jim Schaefer, for their feedback and guidance. I wish to thank Marco
Raponi for collecting and organizing all his flies, and without whose sampling effort
this project would not have been possible. I wish to thank Sherry Wong who gave
countless hours of her summer helping me catalogue and identify my flies. For
someone who didn’t know flies could bite you have come a long way and done an
amazing job. Without you I would probably still be in my basement. Thank you also
to Linda Cardwell for keeping me grounded and maintain a sense of humour over far
too many years. I could not imagine the program without you. Thank you for your
unfailing support.
Thank you to my students and colleagues at St. Michael’s Choir School who
suffered many belated assignments, scattered meetings and physics classes learning
about biting flies.
I especially want to thank my parents and family for their constant support and
encouragement. I wish to thank my children, Beth and Liam, for allowing me to chase
my dream and sacrifice many fun afternoons; and who loved to watch me organize
my army of flies. Thank you for not being afraid of my 10 000 dead insects, yet
strangely terrified of one small live one. I know having a Mamma who’s not around a
lot is hard and I promise we will have many adventures together going forward. I owe
the biggest thank you to Kevin, who is always my biggest supporter and who
provided countless hours of single parenting. Without you I could not have done this,
and I love you more every day for who you let me be. Is this a good time to talk about
the PhD?
iv
I began this journey 15 years ago, and there have been many setbacks. I am
not the same person I was back then, and it is not the same thesis. Through this
journey I have begun a career as a teacher, married, had children, moved continents,
moved continents again, had cancer and tried to live my life to the fullest. That mostly
means life is crazy, unbalanced, exhausting and pretty fantastic. My first attempt at a
master’s degree ended in disillusion and distaste for academic institutions, which I
had loved. Dave really was my inspiration for both my first and a second try at a
graduate degree. As his field assistant in undergrad I spent countless hours in his truck
being quizzed, interrogated and made to explain and develop my ideas. I learnt so
much from those summers. Years later he told me that I could do this, that it wasn’t
too late and that he believed in me to the point that he would be my supervisor.
Almost immediately after I made this decision I was diagnosed with stage III
colorectal cancer. I almost dropped out of the program at that point; I was scared, I
didn’t know if I would live, and I was not sure that spending time focused on
academics versus my family would be the right choice. With my husband’s support I
decided to go forward. It was a really hard two years; I was often sick, tired, under
brain fog, and scared. Having this thesis to work on was hard, but also lifesaving. It
gave me something to focus on and work towards; it kept my brain moving when it
did not want to, and it gave me a goal. Now at the end of my current academic
endeavour I’m not sure what going forward will look like, but this has been an
amazing and important part of my journey.
v
Table of Contents
Abstract………………………………………………………………………..………ii
Acknowledgements…………………………………………………………..……….iii
List of Figures...............................................................................................................vi
List of Tables…………………………………..…...……………………….………viii
Chapter 1: General Introduction.....................................................................................1
Thesis Organization................................................................................................4
Literature Cited….…….……………………………………………………..…..6
Chapter 2: New Range Records of Horseflies and Deerflies (Diptera: Tabanidae)
North of Lake Superior .................................................................................................8
Abstract………………………………………………………………………......8
Introduction……………………………………………………………………....9
Materials and Methods……………………………………………………….....10
Study site…………………………………………………………………....10
Sampling…………………………………………………………………….10
Specimen preparation and analysis……………………………………........11
Results……………………………………………………………………….…12
Large range extensions……………………………………………………..12
Small range extensions……………………………………………………..13
Range gap infills……………………………………………………………13
Phenology…………………………………………………………………..14
Autogeny…………………………………………………………………....15
Discussion………………………………………………………………………16
Literature Cited…………………………………………………………………20
Chapter 3: Land use diversity of Tabanidae species in a 140 km2 study site in north-
central Ontario..............................................................................................................34
Abstract:……………………………………………………………………..….34
Introduction…………………………………………………………………..…35
Materials and Methods:…………………………………………………………38
Study area and study sites………………………………………………......38
Analysis……………………………………………………………………..39
Results…………………………………………………………………………..41
Seasonality…………………………………………………………….……41
Competition…………………………………………………………………43
Seriation..........................................................................................................44
Discussion………………………………………………………………………44
Literature Cited……………………………………………………………..…..49
Chapter 4: General Conclusions...................................................................................66
Literature Cited………………………………………………………………....70
Appendix:…………………………………………………………………………….72
vi
Table of Figures:
Figure 2.1 Detailed Map of Auden Study Site, Ontario. The locations of each
sampling site (with its label) are shown in the inset.. Created by (Raponi et al.,
2018).……………………………………………………………………….…….......23
Figure 2. 2 Map of Ontario showing major range extensions for (a) Chrysops
shermani, (b) Chrysops aberrans and (c) Tabanus fairchildi. The red dot is the
location of the Auden study site and new location of each species. The green areas
show previously known range......................................................................................31
Figure 2.3 Map of Ontario showing minor range extensions for (a) Chrysops calvus,
(b) Chrysops carbonarius (c) Chrysops cincticornis, (d) Hybomitra liorhina, (e)
Chrysops sordidus and (f) Chrysops zinzalus. The red dot, is the location of the Auden
study site and new location of each species. The green areas show previously known
ranges...........................................................................................................................31
Figure 2.4 Map of Ontario showing range in-fills for (a) Hybomitra criddlei, (b)
Hybomitra frosti (c) Hybomitra lasiophthalma, (d) Hybomitra miniscula, (e)
Hybomitra tetrica (f) Hybomitra typhus, (g) Chrysops montanus, (h) Chrysops
striatus, (i) Chrysops indus (j) Chrysops zinzalus and (k) Chrysops cuclux. The red
dot, is the location of the Auden study site, dark green is the known or established
ranges and the light green represents locations found by Ringrose et al
(2014)…………………………..………………………….…...…………………….32
Figure 3.1a The relative abundance of tabanid species (with under 100 specimens) for
2011 and 2012. The x-axis represents days from first observations taken to last of all
species. The y-axis represents numbers of individuals observed. On the y-axis, zero
observations are is recorded in the middle of the vertical axis and any observations is
drawn both up and down vertically, to help visualize population fluctuations. The
scale bar in the first row shows a range of relative abundances from 0-50…………54
Figure 1.1b The relative abundance of tabanid species with 100-1000 specimens for
2011 and 2012. The x-axis represents days from first observations taken to last of all
species. The y-axis represents numbers of individuals observed. On the y-axis, zero
observations are recorded in the middle of the vertical axis and any observations is
drawn both up and down vertically from thereout. This was done to help visualize
population fluctuations. The scale bar in the first row shows a range of relative
abundances from 0-100. ……….…………………………………………………….57
vii
Figure 3.1c The relative abundance of C. excitans for 2011 and 2012. The x-axis
represents days from first observations taken to last of all species. The y-axis
represents numbers of individuals observed. On the y-axis, zero observations are
recorded in the middle of the vertical axis and any observations is drawn both up and
down vertically from thereout. This was done to help visualize population
fluctuations. The scale bar in the first row shows a range of relative abundances from
0-400……………………………...…………………………………………….…….58
Figure 3.2: Stand age preferences by the abundance of species (with over 75
specimens combined for 2011 and 2012)………………………………….…………59
Figure 3.3 Plot of ln(mean) vs ln(variance) of daily trap catches of tabanid species for
three stand ages: 20-35 years (open circles), 36-69 years (black diamonds) and > 70
years (crosses). The slope of the heavy line (open circles, youngest stand) does not
differ from a slope of 2……………………………………………………...………..60
Figure 3.4 Plot of lnmean vs lnvariance of daily trap catches of Chrysops spp (left)
and Hybomitra spp (right) in regions of three stand ages: 20-35 years (open circles),
36-69 years (black diamonds) and > 70 years (crosses) post harvest. The slope of the
heavy line (open circles, youngest stand) does not differ from a slope of 2 for
Chrysops……………………………………………………………………………………….61
viii
Table of Tables:
Table 2. 1: List of tabanid species, summarized through all Auden study sites. Table
shows first and last dates of capture each season, known date range and a total number
captured for 2011 and 2012. Dates of first or last appearance that are outside the
normal range are bolded. Known season dates are from Teskey (1990); the distance to
known range (km to range) is based on ranges in Thomas & Marshall (2009)……...24
Table 2.2 Categorization of tabanids in the Auden study area, Ontario, as autogenous
or anautogenous………………………………………………….....………………...27
Table 2.3 List of species, number of sites (of 62) and total catch for the 8928 tabanids
caught in the Auden study site in northern Ontario…………………………………..29
Table 3.1. Test results for differences in richness and abundance of tabanids in
harvested versus unharvested stands of ANCOVA, using the mean temperature at
each site as the covariate. There were 3 stand ages and 62 sites in total. Ages (years)
of harvested and unharvested stands are noted. ………………………………..62
Table 3.2. Summary of mean abundance and richness of Tabanidae, Hybomitra, and
Chrysops………………....………………………………………………………………………………………63
Table 3.3 Comparison of ln(variance)/ln(mean) slopes in Taylor’s Power Law using a
dummy*X variable…………………………………………………………………...64
Table 3.4. Slopes of ln(variance/ln(mean) for three different stand ages tested against
a slope of 2 using a t-test. Significant p values are for slopes that are less than 2; bold
p-values are those not significantly different from 2…...……………………………65
Table A.1: List of Study sites exclusive to one year of sampling…………………………….72
1
Chapter 1: General Introduction
The species range is the fundamental unit of biogeography (Beres et al., 2005;
Franco, 2013; Riddle and Hafner, 1999). Range information is important because it
helps us ask questions about biological and ecological processes. There are currently
many gaps in species range knowledge, especially in remote locations like Northern
Ontario. These baseline data provide the basis to propose new theories, create models
and link small-focus laboratory work into the larger landscape (Franco, 2013;
Lomolina et al. 2010; Pearson and Dawson, 2003).
Biogeography is the subdiscipline that focuses on the natural history and the
broad-scale distribution of flora and fauna. Biogeography considers an area’s natural
history of there flora and fauna (Riddle and Hafner, 1999). From this knowledge it is
possible to track changes and make predictions for the future (Parmesan et al., 2005;
Pearson and Dawson, 2003). Natural history is a key field of study that has received
negative scientific press in past and has been called stamp collecting and amateur,
amongst other names (Able, 2016; Bury, 2006; Futumya, 1998). Many courses of
study and research have shifted towards laboratory studies that are rigorous and easy
to control or models that attempt to provide causal relationships between trends and
patterns. However, if baseline knowledge about species is not available then there is
no way to verify these discoveries (Able, 2016; Arnold, 2003; Greene, 2005). In
response there has been a revival of this science as the importance of baseline and
deep knowledge about species has been realized. Natural history as a science allows
scientists to understand species ecology and evolution and to pose questions about
development, behaviour and multiple other fields (Able, 2016; Bury, 2006; Grant,
2000).
2
Human use of remote and northern areas in changing constantly, and different
land uses have the potential to alter species use and habitation patterns (Cotterill and
Foissner, 2010; Franklin, 1993; Hins et al. 2009; Peck and McCune, 1997). It is
important to understand how a landscape is being used, how that use is changing
across areas and how that use affects what species will be present. Harvested
landscapes, for example, tend to have lower biodiversity and also more common
species (Hansson, 1992; Hins et al., 2009).
Northern Ontario typifies these challenges. The area, largely untouched, is
increasingly viewed for its resource potential. Northern Ontario is a large area, mostly
uninhabited and where the most common land type is boreal forest. In comparison to
the south of the province, this area is considered to be largely pristine, as it does not
have the same amount of population or resource consumption. This is beginning to
change though as mining, forestry and other resource-based industries are
increasingly moving into northern Ontario. There is a need now to collect data and
insight into this area before changes can occur in greater scale from industry and
create local changes in microclimates and other long-lasting effects such as changes in
global climate patterns.
The deer and horse fly abundance and wide distribution provides a good
opportunity to understand general underlying patterns of species distributions that
occur where there is limited human activity. In northern Ontario, there are about 50-
60 species of Tabanidae, separated into two main subfamilies: Chrysopinae and
Tabaninae (deer flies and horse flies); (Wood, 1985), based on range maps in Teskey
(1990), Thomas and Marshall (2009), and Thomas (2011). There are no non-native
species of this family known to be present in the study area (CESCC, 2016) and their
current distribution is a result of post-glacial colonization (Danks, 1979)
3
Species from this family are capable of tormenting humans and many large
mammals such as moose (Alces alces), woodland caribou (Rangifer tarandus), black
bear (Ursus americanus) or birds, amphibians, and reptiles (Wood 1985). They also
form an important part of the ecosystem and are an abundant source of food for many
of the same wildlife (Teskey 1970). While many species are blood feeders, there are
some that can also be nectar feeders, and therefore could also act as secondary
pollinators (Teskey, 1990).
Hybomitra and Chrysops are two of the larger genera within the Tabanidae.
Members of both are predominantly obligate blood-feeding Diptera (anautogenous
species), although some species are facualtive blood feeders (the autogenous species).
They are found across northern Ontario. Their last common ancestor was just after the
Mesozoic and their worldwide distribution, primarily in northern climes, has followed
the distribution of mammals (Mackerras, 1954). There is no information on preferred
hosts, but the mouthparts are similar within this group (Teskey, 1990) so it can be
inferred that they attack similar host species.
Tabanids reproduce at least once a year, and respond quickly to habitat and
environmental change (Blickle, 1955; Krcmar, 2005; Mackerras, 1954; Ringrose,
2014). This makes them a great signature of change and useful for identifying patterns
that are occurring across many species, but difficult to see in more slowly reproducing
species (MacMahon et al., 2000). Knowledge of the ranges of Tabanid species
enables us to understand climate and land use change through range shifts. This is the
geography of the signature of changes.
One of the most pressing reasons for the immediate baseline knowledge of
species is climate change. There is no environment on earth that has been left
untouched by humans and it will be impossible to know the pristine state of species.
4
As we begin to see and acknowledge the effects of climate change on species
distributions, we need to capture a current view of environments to monitor that
change (Davis and Shaw, 2001; Nimmo et al., 2015; Pearson and Dawson, 2003). In
northern climes, the rate of change due to anthropogenic climate forcing will be even
faster than in more temperate areas as temperature rises disproportionately towards
the poles (Alexeev et al., 2005; Bekryaev et al., 2010). Northern Ontario has fewer
species in comparison to equatorial regions, but this may make monitoring easier as
species have broader ranges and are often found in similar assemblages (Davis and
Shaw, 2001).
The study area was located just north of Lake Nipigon at the Ontario Ministry
of Natural Resources and Forestry (OMNRF) Auden study site in North-central
Ontario (50° 15'N, 87° 54'W). The Auden site is defined by a 140 km2 section of
boreal forest in the Lake Nipigon drainage basin. The landscape type is mostly patchy
stands of black spruce, jack pine and balsam fir (Abies balsamea) intermittent
between grassy lowlands (Raponi et al., 2018). There is also an extensive network of
small lakes and rivers throughout the site.
Thesis Organization
This thesis has a general introduction, two research chapters, and a general
discussion. The first research chapter (Chapter 2) summarizes important range
extensions and new range records that I found for Tabanidae from the Auden region
of northern Ontario. In this chapter, I report numbers of each species and their relative
abundance (the latter a measure of the adaptations of each species to the
site/environment). In Chapter 3, I look at how the Tabanidae in Chapter 2 use the
landscapes available near the Auden Study site in terms of their total abundance,
relative abundance and dates of appearance and disappearance. The type of landscape
5
as well as age of stand is examined. This is done in order to discern species, genera
and feeding strategy patterns and common land use evolutionary strategies shared
between species. I discuss and summarize my work with a general discussion and
conclusion.
This research has two objectives:
1. To examine the natural history of different tabanid species through their abundance,
distributions, seasonality and diversity in an area with minimal human activity and
previous study. This is important because it will inform basic species knowledge
about the flies and act as a baseline prior to additional disturbance from climate
change or human development. This baseline information can be used to monitor the
effects of human and environmental change on the insects and provide an analog to
other species.
2. To examine a hypothesis connecting land-use to competition strategies in
Tabanidae. This is important because forest in Ontario often has a history of
disturbance and harvest. Since both tabanids and their prey live in the forest area it is
reasonable to consider how harvest history may effect their interactions.
6
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8
Chapter 2: New Range Records of Horseflies and Deerflies (Diptera:
Tabanidae) North of Lake Superior
Abstract
There are gaps in the knowledge of species in Northern Ontario. The species range is
a basic and important piece of knowledge that creates the foundation for further
research. Tabanids provide a unique opportunity for observation as the group is
widespread across the near north of Ontario and has rapid reproduction, making them
suitable to detect rapid environmental change In northern Ontario a total of 44 species
were captured by sweep netting throughout the two years of sampling. Major range
extensions, of more than 450 km, were observed for Chrysops shermani, C. aberrans
and Tabanus fairchildi. C. shermani had over 150 individuals collected over the
sampling time indicating a likely breeding population in the study area. Minor range
extensions (<400 km) and range in-fills were observed for a further 15 species. Six of
the in-fills — Hybomitra criddlei, H. frosti, H. lasiophthalma, H. minuscula, H.
tetrica and H. typhus — are new northern additions found here and in the extreme
northwest and northeast of the province (Ringrose et al., 2014). H. typhus in particular
is a rarely recorded species with only nine other known locations. Temporal extension
of season was also observed for a number of species: 11 species were recorded more
than a week earlier than previous records and another 11 species were recorded more
than a week later than previous records. Chrysops ater was found August 25, nearly
two months after its previously published end of season. Chrysops carbonarius was
the only species that was captured both earlier and later than previously known
records. As land use pressures accelerate, there is increased pressure to create baseline
knowledge from which to monitor and observe changes.
9
Introduction
The species range is the fundamental piece of knowledge in ecological
research (Lomolino et al., 2010; Pearson and Dawson, 2003; Webb et al., 2002).
Knowing a species range provides baseline data that can highlight current knowledge
gaps, allow for future monitoring, and make possible the tracking of changes in
species ranges (Colwell et al., 2008; Sagarin et al., 2006). Species ranges monitored
over time could reveal changes in phenology that could be caused by changes in
climate (Davis and Shaw, 2001; Parmesan et al., 2005; Pearson and Dawson, 2003;
Thuiller, 2004). For insects, the fast generation time of most common species make
this group an ideal candidate for tracking rapid responses to habitat change (Devictor
et al., 2012; Pereira and Cooper, 2006; Spellerberg, 2005).
Insects within the family Tabanidae provide such an example, because they
are widespread, easy to capture and have a short generation time. This group includes
horse flies and deer flies. The first comprehensive report on Canadian tabanids was
created in 1961 (McElligott and Galloway, 1991), with important recent additions by
Teskey (1990), Thomas and Marshall (2009), Thomas (2011), and most recently,
Ringrose et al. (2014).
Northern Ontario is a blank space on the reports mentioned above. To add to
this body of data, the Ontario Ministry of Natural Resources and Forestry (OMNRF)
Auden study site, 100 km north of Lake Nipigon, Ontario, was chosen. This region
contains sections that have a variable history of logging at different times as well as
some unharvested areas (Raponi et al., 2018). Tabanids are visual predators and the
density of a forest stand could affect their ability to hunt and therefore where they are
located. Tree density is affected by an areas logging history. This makes Auden ideal
10
for monitoring species across different habitats, especially in terms of harvest history,
but within the same climatic region.
In this study I identified species of Tabanidae that were previously caught in
this region as part of a biting fly caribou study (Raponi et al., 2018). These samples
were obtained by sweep netting insects that were flying around the researchers in
different habtiats. This collection method generally only catches species easily
obtainable, those attracted to humans. I have analysed these data in terms of
phenology, autogeny status, abundance, and related these to timber harvest history, as
well as report on new records that extend the known range of several species.
Materials and Methods
Study site
In 2011 and 2012, deer fly and horse fly species were sampled from the
OMNRF’s Auden Study site just north of Lake Nipigon in north-central Ontario (Fig..
2.1). The study area was located adjacent to Lake Nipigon (50° 15'N, 87° 54'W). This
is a 140 km2 section of boreal forest in the Lake Nipigon drainage basin. The site has
an extensive group of rivers and small lakes, patchy pine and spruce stands and grassy
lowlands. There is also a history of forest harvesting and railway lines in the area that
has led to the creation of roads, harvested and replanted stands (Raponi et al., 2018).
Sampling
Sampling sites are representative of the wide variety of the managed and
unmanaged habitats and were chosen based on accessibility. Detailed site descriptions
and location information can be found in Raponi et al. (2018). In 2011, weekly
samples were collected from 57 sites between 31 May – 18 August. In 2012, weekly
samples were collected from 63 sites between 31 May – 25 August. Site visits were
grouped by location to allow researchers to drive to as many sites as possible each
11
day. Sampling was conducted at 69 sampling sites, 51 of which were sampled in both
years (Appendix).
Tabanids were sampled approximately once per week through the entire
season by sweep netting; a detailed procedure is described in Raponi et al. (2018).
The time of day of capture was systematically varied at sites between 07:00-20:00 in
order to sample flies during peak activity and remove the effect of diurnal variation in
tabanid activity. At each location two field personnel with sweep nets walked through
the middle of the site and then walked slowly side by side, leaving enough distance to
not entangle nets, approximately 1-2 m apart. The nets were swung in a Figure-eight
pattern. The researchers continued to sweep for a total of 5-10 minutes after reaching
the centre of a site. Site centres were marked and sweepers remained in motion near
those marks during the active capture phase. Once this was completed, the ends of the
net bags were placed in killing bottles charged with acetone. Once dead specimens
were removed from the net, they were stored in bottles filled with 80% denatured
ethanol. The denatured ethanol in each bottle was replaced once after 24 hours.
Specimen preparation and analysis
When the specimens were removed from the denatured ethanol for pinning,
they were first processed through a 50% ethanol, 50% acetone solution for 24 hours;
then a 100% acetone solution for an additional 24 hours. This was done to remove any
traces of ethanol and maintain specimen colouring (Vockeroth, 1966). All tabanids
were pinned and identified by Janette Buckley, Marco Raponi and David Beresford
using keys found in Teskey (1990), Thomas and Marshall (2009) and Thomas (2011).
Tabanids are primarily identified by a combination of features including body colour,
wing design and mouthparts. The main pinned collection is stored in insect cabinets at
Trent University, Biology Department, Peterborough, Ontario. Each insect received a
12
unique catalogue number that links the individual specimen to its location in the
collection as well as sample meta-data. A reference collection of voucher specimens
was submitted to the Canadian National Collection of Insects, Arachnids and
Nematodes, Ottawa. I used the following sources to determine whether species
collected were within or outside of the published ranges: Teskey (1990), Thomas and
Marshall (2009), Thomas (2011) and Ringrose et al. (2014). Habitats were determined
using Ontario Land Classifications as published by the OMNRF (2002). The samples
and land information were compiled by Raponi et al. (2018). Tabanidae species were
categorized as autogenous (non-obligate blood feeders) or anautogenous (obligate
blood feeders) based on published records (Lake and Burger, 1980; Leprince and
Maire, 1990; McElligott and Lewis, 1998; Thomas, 1971; Troubridge and Davies,
1975). Chi-square tests were conducted to determine if species abundance (for any
species with >40 individuals) was linked to either likelihood of range or season
extension. I compared total catch of autogenous and anautogenous species and the
total number of sites with autogenous and anautogenous species using a chi-squared
test. I used an alpha level of 0.05 to denote significance.
Results
I identified 44 species in 4 genera from across the study area: 1 species of
Atylotus, 20 Chrysops, 20 Hybomitra, and 3 Tabanus. Of these, 18 species’ ranges
were extended as a result of this study: 10 species of Chrysops, 7 Hybomitra and 1
Tabanus. There were 8928 individual specimens captured and identified, only 8 of
which were males: 4 Hybomitra lasiophthalma, 2 Hybomitra epistates, 1 Hybomitra
affinis and 1 Hybomitra frontalis. From the published accounts of currently known
ranges (Ringrose et al. 2014, Teskey 1990, Thomas 2011, Thomas and Marshall
2009), I expected to find up to 60 species in this study area, using the criteria of either
13
having known ranges that encompass the study area (9 species of Chrysops, 19
Hybomitra, 3 Atylotus, 3 Tabanus) or having previously been recorded within 300 km
(11 species of Chrysops, 1 Haematopota, 8 Hybomitra, 3 Atylotus, 2 Tabanus).
Large range extensions
Three species were found that extend the known range by more than 450 km.
Chrysops shermani (Hine) is found through the Maritimes and southern Ontario, with
current records extending no further north than the northern edge of Lake Huron
(46°17’N, 83°47’W) (Thomas & Marshall, 2009) (Figure 2.2a). The capture of this
species from the Auden study site constitutes a northwest extension of the range of
approximately 600 km. As 158 specimens of C. shermani were captured over the two
years of sampling, it is likely that this species breeds in the Auden study site.
One specimen of Chrysops aberanns was found 7 July 2011. The known range
of C. aberanns and the extension of this range is similar to those for C. shermani
(Figure 2.2b). Two Tabanus fairchildi were caught, 1 each year. While common in
southwestern New Brunswick, only 3 Ontario locations are known. The furthest north
previously reported location is near Lake Timiskaming (47° 36′ N, 79° 29′W ) 650 km
east-southeast (Figure 2.2c) (Thomas, 2011).
Small range extensions
Along with the three major range extensions, there were a number of minor
northern range extensions (<300 km), extending the northern range limits from Lake
Superior to Auden. Chrysops calvus (Figure 2.3a), C. carbonarius (Figure 2.3b), and
C. cincticornis (Figure 2.3c) were all found at Auden, 100-300 km north of the
previously reported ranges. There are no known locations further north or east in the
province. H. liorhina (Philip) (Fig. 2.3d) was found about 100 km north of its
previously known range. A capture of C. sordidus from our Auden study site has
14
extended the known northwest part of the range around Lake Nipigon. Previous to this
study, C. sordidus has been found at similar latitudes, or further north, in Quebec and
Labrador. My samples are the first documentation of C. sordidus this far north in
Ontario, as shown in Figure 2.3e (Thomas and Marshall, 2009).
Range gap infills
This study, combined with Ringrose et al. (2014), provide new range evidence
for: Hybomitra criddlei (Brooks) (Figure 2.4b), and H. frosti (Figure 2.4c). H.
lasiophthalma (Macquart) (Figure 2.4d), H. minuscula (Hine) (Figure 2.4e), H. tetrica
(Marten) (Figure 2.4f) and H. typhus (Whitney) (Figure 2.4g). The locations found
with H. frosti, H. minuscula and H. typhus by Ringrose et al. (2014), plus my work,
represent a significant extension (minimum 450 km) of ranges for those three species.
(Ringrose et al., 2014)’s study areas were in the extreme northwest, bordering
Manitoba, and northeast, bordering James Bay, of Ontario. H. typhus is also relatively
rare and previously known from only 8 locations in Ontario and Quebec and more
commonly found in the Maritimes (Teskey, 1990; Thomas, 2011). C. montanus is a
range infill of about 300 km from the closest known occurrence to the west and 700
km to the east (Fig. 2.4g). A similar range infill occurred for C. striatus (Fig. 2.4h)
similar to C. montanus. C. indus is an infill of about 400 km from both the east and
west of its previously known ranges (Fig. 2.4i). Chrysops zinzalus is primarily an
eastern species with two occurrences in Alberta. This sighting helps to bridge the
considerable gap in known occurrences (Fig. 2.4j). The Auden capture is just outside
the eastern likely range of the species so this sighting helps to build evidence of more
extensive further range. C. cuclux has been found from 3 locations to the southwest of
Lake Nipigon as well as at a similar latitude much further east in Ontario near the
border with Quebec (Fig. 2.4k). A Fisher’s exact test (2x2, df=1, p=0.24, 2, 6, 20, 16)
15
showed that there was no statistical difference between common (>40 individuals)
and uncommon species in the data set.
Phenology
Tabanids were present throughout the sampling seasons in 2011 and 2012,
from 31 May – 18 August (2011) and August 25 (2012) which represented a period
that mean daily temperatures were above 0 oC for the Auden study area.Both 2011
and 2012 were warm years with above 0°C days happening in mid-March and the
average temperature above 0°C by mid-April. Many of the species exhibited seasonal
ranges outside those reported in the literature. Twelve species had earlier occurrences,
from 1-3 weeks previous to those reported in the literature, while 12 species had later
(Table 2.1). The most notable was an extension of the season was for C. ater, which
was found almost 2 months later than the previous record (early July versus late
August (Aug 25th
). This species may have been active even later than our last date of
sampling. Only Chrysops carbonarius had its season extended on both sides by at
least 2 weeks. The most significant extensions though were the additions to the end of
the season; many of these were in the range of 6 weeks to 2 months. A chi-square
analysis of commonality (2x2, df=1, p=0.13, 7, 15, 12, 10) and extention of season
(2x2, df=1, p=0.11, 17, 5, 12, 10) showed no significant difference .
Autogeny
Of the 44 Tabanidae species, 12 are known to be autogenous and 14
anautogenous (Table 2.2). Anautogenous species were 2.2 times more abundant than
autogenous species and caught in 1.9 times as many sites as autogenous species
Fisher’s Exact tests showed that there were no significant differences between
autogenous and anautogenous species in regards to commonality (2x2, df=1, p=0.66,
10,9,5,2), or site distribution (2x2, df=1, p=0.63, 6,1,13,6).
16
Discussion
Northern Ontario covers a vast area, and compared to southern Ontario, there
are relatively few such intensive studies of tabanid species distribution, hence it was
expected that my study would document range extensions. Half of Chrysops species
had their ranges extended, and a third of Hybomitra. Eight of the extended species had
very low numbers. Of these only one species, H. liorhina, was a singleton. While it is
possible these might simply be wind borne migrants that were carried to the Auden
study site on weather systems, this is unlikely. Any occasional would have to be
transported by wind, dropped during a rainfall event at random onto the landscape.
For them to arrive into suitable habitat, and for us to have caught a single specimen of
a species that was picked up by an updraft and carried several hundred kilometres to
be dropped from the sky onto where we were collecting seems improbable. It is far
more likely that these low catches are due to undersampling and one of two reasons:
1) either low overall abundance, or 2) low hostseeking response. If the latter, low
catches could arise if the hosts (the field technicians) were at the edge of a preferred
habitat for these species, at the wrong time for these species, or if these species have a
lower or delayed hostseeking response. I can dismiss the wrong season argument, for
sampling took place over two years over the majority of the tabanid season, and
included early and late catches with no tabanids being caught. This leaves the low
abundance or low hostseeking response arguments. Both of these arguments relate to
the specific niches of these species; low abundance would be expected for specialist
species, and similarly, specialized hostseeking strategies would also be expected
(Hubbell, 2001). In both these cases a tremendous catch effort would have to be put in
place in order to represent these species abundance more accurately (Coddington et
al., 2009).
17
Early seasonal activity was detected for 11 species, with activity observed
about two weeks earlier than reported in the literature (Teskey 1990). In past, species
such as H. frontalis are expected to appear later in spring when found at the northern
edge of their range. This is likely due to the later arrival of warmer temperatures and
ice-free water for breeding in comparison to lower latitudes. However, in 2011 and
2012 mean temperatures over 0°C began to occur as of 16 March 2011 and minimum
temperatures over 0°C by mid April 2011 (Armstrong Ontario weather data
Environment Canada 2016). By the end of April 2011 mean temperatures were
consistently over 0°C. Similarly, during the following year, 10 March 2012 was the
first day with a mean temperature over 0°C, and minimum temperatures began to rise
above 0°C almost immediately afterwards (Environment Canada, 2016). March 2012
was an exceptionally warm month (Sanders, 2014).
Twelve species also had their seasons extended at the end of the season by a
minimum of two weeks later than published accounts (Teskey 1990), and my records
of C. carbonarius were both earlier and later than expected. This may have been
because the species is rarely caught (Teskey 1990), so little information is available
about its seasonality.
What is not known is what signals the onset of adult tabanid activity in an area
— whether it occurs once the daily temperature rises above taband species’ flight
threshold temperatures, or if there is a time lag in species response after brief warm
weather events with adult emergences, or even how long such a warming event must
be to trigger new adult emergence. Changing climates are likely influencing tabanid
seasons and producing seasonal extensions (Davis and Shaw, 2001; Pearson and
Dawson, 2003). If season extension were simply a factor of climate changes or
location, one would expect to see range extensions on either side of the season, or
18
consistently on the earlier side. However, without this basic biological understanding
of different tabanid life history responses, any assessment of climate changes in an
area or climate impacts is difficult to interpret.
Insect activity, mating, oviposition, and maturation are largely controlled by
temperature, with insects active in warm weather but almost completely inactive in
cold weather (Foil and Hogsette, 1994; Herczeg et al., 2015). Due to the short ice-free
breeding season in northern Ontario, tabanids may emerge and populations grow
quickly and maintain their numbers until a sudden drop in temperature in the fall
causes a rapid drop in abundance (Colwell et al., 2008; Krüger and Krolow, 2015;
Rueda et al., 1990).
Catching host-seeking anautogenous species was expected. Because females
from these species require blood to lay eggs, the abundance we observed may not
necessarily reflect abundance within the habitat, but can be understood as harassment
abundance (Ringrose et al., 2014). These results do not necessarily translate to
relative abundance in terms of other ecological interactions such as predators (as
larvae) or as prey for other wildlife. Nevertheless, for humans and wildlife, knowing
exact abundance in a habitat is unimportant compared to harassment abundance or
pest abundance. Clearly the most widespread and abundant pests in the sampled
region are the anautogenous species. For example, C. excitans, which was found in all
sites that had flies (Table 2.3), made up 34% of all tabanids caught. However,
autogenous species were also evident; the second most abundant species, C. mitis, is
autogenous. The abundance of anautogenous species means that breeding populations
are clearly obtaining sufficient bloodmeals from wildlife to ensure their continued and
abundant presence (Raponi, 2014). In general a large and diverse community of
tabanids lives around the Auden study site. Species have been discovered in
19
previously unknown ranges and a number of seasons were extended beyond
previously known dates. This adds to the general body of knowledge and presents an
important baseline for future studies.
20
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23
Figure 2.1 Detailed map of Auden Study site, Ontario. The locations of each sampling
(with its label) are shown in the inset. Created by (Raponi 2014).
24
Table 2.1: List of tabanid species, summarized through all Auden sampling
sites. Table shows first and last dates of capture each season, known date range and a
total number captured for 2011 and 2012. Dates of first or last appearance that are
outside the normal range are bolded. Known season dates are from Teskey (1990); the
distance to known range (km) is based on ranges in Thomas & Marshall (2009).
Species 2011 2012
1st
occ
urr
ence
Last
occ
urr
ence
Tota
l C
au
gh
t
1st
occ
urr
ence
Last
occ
urr
ence
Tota
l C
au
gh
t
Known Season Distance
to
known
range
(km)
Tabanus fairchildi 13-Jy 13-Jy 1 3-Jy 3-Jy 1 July – early Aug 650
Hybomitra frosti 3-Jn 17-A 98 3-Jn 25-A 149 early July-late Aug 500
Hybomitra typhus 7-Jn 17-A 34 31-M 25-A 51 10th June – 10
th Aug 500
Chrysops aberrans 7-Jy 7-Jy 1 0 late May – Sept 450
Chrysops shermani 9-Jn 15-A 136 3-Jn 7-A 22 mid June – mid Aug 450
Chrysops indus 9-Jn 15-Jy 32 4-Jy 2-A 5 late May – early
Aug
400
Hybomitra minuscula 2-Jn 2-A 10 13-Jn 25-A 32 late June – end Aug 400
Chrysops cincticornis 30-Jn 30-Jn 1 0 late May – Aug 300
Chrysops montanus 30-Jn 12-Jy 8 5-Jy 11-Jy 2 late June – mid Aug 300
Chrysops striatus 14-Jn 12-Jy 5 5-Jn 1-A 2 24th June – 25
th Aug 300
Chrysops zinzalus 3-Jn 2-A 15 10-Jn 25-A 12 mid June – late Aug 250
Hybomitra tetrica 12-Jn 1-A 6 19-Jn 19-Jn 2 late May – mid Aug 250
Chrysops carbonarius 31-M 23-Jy 32 3-Jn 25-A 44 mid June – mid July 150
25
Chrysops sordidus 0 10-Jn 25-A 4 early June – late
July
150
Chrysops calvus 6-Jn 13-Jy 5 12-Jn 23-A 6 early June – mid
July
100
Chrysops cuclux 31-M 6-A 325 10-Jn 25-A 126 late May – mid July 100
Hybomitra criddlei 29-Jn 18-A 34 5-Jn 18-A 30 mid June – July 100
Hybomitra liorhina 0 22-Jy 22-Jy 1 early July – mid
Aug
100
Hybomitra
lasiophthalma
31-M 18-A 79 2-Jn 23-A 106 late May – end July 50
Atylotus sublunaticornis 3-Jn 3-Jn 1 0 early June - late July 0
Chrysops ater 2-Jn 17-A 48 31-M 25-A 101 mid May – early
July
0
Chrysops dawsoni 2-Jn 17-A 191 31-M 25-A 185 early June – end of
Aug
0
Chrysops excitans 31-M 18-A 1386 31-M 25-A 1619 Early June – end of
Aug
0
Chrysops frigidus 3-Jn 17-A 23 31-M 7-A 26 mid June – end of
July
0
Chrysops furcatus 3-Jn 15-A 14 6-Jn 2-A 13 mid June – mid Aug 0
Chrysops mitis 31-M 17-A 347 31-M 25-A 615 late May – Sept 0
Chrysops niger 0 5-Jy 18-A 2 1st June – early Aug 0
Chrysops nigripes 6-Jn 15-A 4 11-Jn 25-A 3 late June – mid Aug 0
Chrysops venus 6-Jn 15-A 29 2-Jn 25-A 28 2nd
June – 2nd
Sept 0
Hybomitra arpadi 31-M 6-Jy 6 15-Jn 22-Jy 8 mid June – mid Aug 0
Hybomitra astuta 9-Jn 10-A 13 5-Jn 25-A 23 mid June – mid Aug 0
Hybomitra epistates 2-Jn 18-A 58 31-M 25-A 90 early June – early
Aug
0
Hybomitra frontalis 2-Jn 18-A 253 31-M 25-A 342 late May – Sept 0
26
Hybomitra hearlei 2-Jn 29-Jy 10 31-M 25-A 18 2 June – 14 Aug 0
Hybomitra illota 31-M 18-A 120 2-Jn 25-A 113 late May – early
Aug
0
Hybomitra longiglossa 6-Jy 6-Jy 1 0 late May – early
Aug
0
Hybomitra lurida 31-M 18-A 22 8-Jn 23-A 30 late May – early
Aug
0
Hybomitra nuda 31-M 18-A 315 31-M 24-A 398 mid May – mid July 0
Hybomitra pechumani 31-M 17-A 305 31-M 25-A 447 mid June – end Aug 0
Hybomitra trepida 2-Jn 17-A 28 31-M 25-A 38 early June – late
Aug
0
Hybomitra zonalis 2-Jn 18-A 20 3-Jn 21-A 26 early June – mid
Aug
0
Hybomitra affinis 3-Jn 18-A 86 31-M 23-A 84 2nd
June – 20th
Aug 0
Tabanus marginalis 6-Jn 14-Jy 6 3-Jy 25-A 3 early June – late
Aug
0
Tabanus reinwardhii 9-Jn 9-Jn 1 0 mid June – end Aug 0
27
Table 2.2 Categorization of tabanids in the Auden study area, Ontario, as autogenous
or anautogenous.
Species Autogenous = 0,
Anautogenous = 1
Reference*
A B C D E
Chrysops ater 0 0
Chrysops cincticornis 0 0
Chrysops cuclux 0 0
Chrysops excitans 1 1
Chrysops frigidus 0 0
Chrysops furcatus 1 1
Chrysops mitis 0 0 1
Chrysops niger 0 0
Chrysops nigripes 0 0
Chrysops zinzalus 0 0
Hybomitra affinis 1 1 1
Hybomitra arpadi 1 1 1 1
Hybomitra astuta 0 0
Hybomitra epistates 1 1 1
Hybomitra frontalis 0 0 0 0
Hybomitra hearlei 0 0 0
Hybomitra illota 1 1 1
Hybomitra lasiophthalma 1 1 1 0 1
Hybomitra liorhina 0 0 0
Hybomitra lurida 1 1 1 0
Hybomitra nuda 1 1 1
Hybomitra pechumani 1 1 0
Hybomitra tetrica 1 1
28
Hybomitra typhus 1 1 1
Hybomitra zonalis 1 1 1 0
Tabanus reinwardtii 0 0
*A = Thomas (1971); B Troubridge and Davies (1975); C Lake and Burger (1980); D
LePrince and Maire (1990) E McElligott and Lewis (1998)
29
Table 2.3 List of species, number of sites (of 62) and total catch for the 8928 tabanids
caught in the Auden study site in northern Ontario.
Sorted by name
Sorted by catch size
Species
Number
of sites
Total
catch
Species
Number
of. sites
Total
catch
Atylotus
sublunaticornis 1 1
Chrysops excitans 62 3005
Chrysops aberrans 1 1
Chrysops mitis 59 962
Chrysops ater 38 149
Hybomitra
pechumani 59 752
Chrysops calvus 8 11
Hybomitra nuda 59 713
Chrysops
carbonarius 30 76
Hybomitra frontalis 57 595
Chrysops
cincticornis 1 1
Chrysops cuclux 27 451
Chrysops cuclux 27 451
Chrysops dawsoni 53 376
Chrysops dawsoni 53 376
Hybomitra frosti 46 247
Chrysops excitans 62 3005
Hybomitra illota 44 233
Chrysops frigidus 24 49
Hybomitra
lasiophthalma 49 185
Chrysops furcatus 17 27
Hybomitra affinis 47 170
Chrysops indus 9 37
Chrysops shermani 18 158
Chrysops mitis 59 962
Chrysops ater 38 149
Chrysops
montanus 4 10
Hybomitra
epistates 49 148
Chrysops niger 2 2
Hybomitra typhus 31 85
Chrysops nigripes 7 7
Chrysops
carbonarius 30 76
Chrysops shermani 18 158
Hybimotra trepida 30 66
Chrysops sordidus 2 4
Hybomitra criddlei 29 64
Chrysops striatus 5 7
Chrysops venus 32 57
Chrysops venus 32 57
Hybomitra lurida 29 52
Chrysops zinzalus 19 27
Chrysops frigidus 24 49
Hybomitra affinis 47 170
Hybomitra zonalis 25 46
Hybomitra arpadi 11 14
Chrysops indus 9 37
Hybomitra astuta 21 36
Hybomitra astuta 21 36
Hybomitra criddlei 29 64
Hybomitra hearlei 19 28
Hybomitra
epistates 49 148
Chrysops furcatus 17 27
Hybomitra
frontalis 57 595
Chrysops zinzalus 19 27
Hybomitra frosti 46 247
Hybomitra
miniscula 9 21
30
Hybomitra hearlei 19 28
Hybomitra arpadi 11 14
Hybomitra illota 44 233
Chrysops calvus 8 11
Hybomitra
lasiophthalma 49 185
Chrysops montanus 4 10
Hybomitra
liorhina 1 1
Tabanus
marginalis 7 9
Hybomitra
longiglossa 1 1
Hybomitra tetrica 5 8
Hybomitra lurida 29 52
Chrysops nigripes 7 7
Hybomitra
miniscula 9 21
Chrysops striatus 5 7
Hybomitra nuda 59 713
Chrysops sordidus 2 4
Hybomitra
pechumani 59 752
Chrysops niger 2 2
Hybomitra tetrica 5 8
Tabanus fairchildi 2 2
Hybimotra trepida 30 66
Atylotus
sublunaticornis 1 1
Hybomitra typhus 31 85
Chrysops aberrans 1 1
Hybomitra zonalis 25 46
Chrysops
cincticornis 1 1
Tabanus fairchildi 2 2
Hybomitra liorhina 1 1
Tabanus
marginalis 7 9
Hybomitra
longiglossa 1 1
Tabanus
reinwardtii 1 1
Tabanus
reinwardtii 1 1
31
Figure 2.2 Map of Ontario showing major range extensions for (a) Chrysops shermani,
(b) Chrysops aberrans and (c) Tabanus fairchildi. The red dot is the location of the
Auden study site and new location of each species. The green areas show previously
known range.
Figure 2.3 Map of Ontario showing minor range extensions for (a) Chrysops calvus, (b)
Chrysops carbonarius (c) Chrysops cincticornis, (d) Hybomitra liorhina, (e) Chrysops
sordidus and (f) Chrysops zinzalus. The red dot, is the location of the Auden study site
and new location of each species. The green areas show previously known ranges.
a b c
a b c
d e f
32
a b
c
d e f
g h i
j
33
Figure 2.4 Map of Ontario showing range in-fills for (a) Hybomitra criddlei, (b)
Hybomitra frosti (c) Hybomitra lasiophthalma, (d) Hybomitra miniscula, (e) Hybomitra
tetrica (f) Hybomitra typhus, (g) Chrysops montanus, (h) Chrysops striatus, (i) Chrysops
indus (j) Chrysops cuclux. The red dot, is the location of the Auden study site, dark green
is the known or established ranges and the light green represents locations found by
Ringrose et al (2014).
34
Chapter 3: Land use diversity of Tabanidae species in an 140 km2 study site in
north-central Ontario
Abstract
The differences in land use patterns of Hybomitra and Chrysops species (Diptera:
Tabanidae) collected in a 140 km2 study site in northern Ontario were compared. at the
Ontario Ministry of Natural Resources Auden study site, Ontario (50° 15'N, 87° 54'W).
The study site, Auden, just north of Lake Nipigon represents an area of boreal forest with
a mixed use history. Forest stands range from those which are recently harvested (25-39
years) to mature lots (>69 years). We examined data on Tabanid (Chrysops and
Hybomitra) biting flies to ascertain stand age preference and seasonal partitioning of
landscape use by different species. It was hypothesized that younger stands would
experience greater competition amongst flies and that flies would be found with greater
diversity in mid and older aged stands. In general, all species were collected across a
wide range of landscapes and broad times of the summer season and no significant
difference could be detected among species. A preference amongst harvested stands was
seen where overall, harvested stands had 50 % more individuals and a 30% greater
species richness. Chrysops excitans, an aggressive large mammal host-seeking species,
which accounted for about a third of individuals collected, favoured stands less than 70
years old(p<0.01). Implications of this research may indicate further interactions between
forest harvesting and pest avoidance and stress responses of large mammals such as
Rangifer tarandus using these intermediate aged stands for food and/or predator
avoidance(Raponi et al., 2018).
.
35
Introduction
Disturbances such as harvesting in forests can alter habitats for many species,
while providing new opportunities for others. Often it is pest species that benefit from
such effects, and these in turn can further stress vulnerable and threatened populations
(Nadeau et al., 2016). Horse flies and deer flies (Tabanidae) are good candidates for a
model of how species composition can change with forest harvesting: they respond
quickly to environmental change, due to their short generation time and can serve as
indicators of changes with other biota (Brown 1991, Kremen et al. 1993, Kremen 1994).
The primary objective of this paper is to see how tabanid species differs over the season
and different forest stand ages. Such knowledge is important because Tabanid harassment
can alter the behaviour of large mammals such as woodland caribou (Raponi et al. 2018).
In this paper, I use previously collected specimens obtained by Raponi (2014) as part of
his thesis research.
Northern Ontario is a sparsely populated region, whose industries include forestry
and mining. Northern regions are potentially sensitive to the effects of climate change
(Alexeev et al., 2005; Bekryaev et al., 2010). The opportunity to observe natural insect
communities now may be a good point of comparison as the climate and landscape
become increasingly affected. The Ontario Ministry of Natural Resources and Forestry
(OMNRF) Auden study site, which houses over 40 species of Tabanids (Chapter 2), in
Northern Ontario is about 100 km north of Lake Nipigon and contains, within a small
area, multiple different forest types including mature (over 70 years old), 30-60-year-old
stands and stands harvested less than 30 years ago. Timber in this area has been harvested
for over 100 years. Harvesting included coniferous, mixed and deciduous trees. This
36
variety in habitats allowed me to test for differences in numbers of tabanids captured
among habitats over one geographic region. Stand age is highly correlated with forest
canopy cover and strong species preferences in tabanids among habitats with different
amounts of forest cover have been documented (Ford et al., 2000).
Habitats that are less densely covered in trees are generally preferred by larger
mammalian species that can move freely through these types of habitat, browsing on
accessible leafy vegetation (Hins et al., 2009). Raponi et al. (2018) found that the
presence of flies can reduce the activity of caribou. If more were known about tabanid
preferences it could inform harvesting strategies. The goal of my research is to determine
the preferences of tabanid species among stands of varying times since harvest.
Insects, like all animals, choose habitat for a variety of reasons (Foil and
Hogsette, 1994; Mikuska et al., 2012; Teskey, 1990). Within the habitat, they must be
able to eat, find shelter and protection from predators, mate and reproduce. Many biting
flies have preferences towards mammals or birds, large or small wildlife (Hins et al.,
2009; Teskey, 1990; Wood, 1985). These feeding preferences will likely determine what
type of landscape they occupy as their hosts have different space requirements,
particularly tree density. For example, larger ungulates such as moose prefer denser forest
while white-tail deer like younger forest and grasslands (Bergerud, 1974; Hins et al.,
2009). Often habitat preferences are not well known for smaller species of invertebrates,
especially for insect species which are often less studied (Greene, 2005; Johnson and
Stinchcombe, 2007). When habitat preferences are known, we may be able to predict
some of the changes that may occur to the species abundance and distribution due to
human habitation, forestry, mining and climate change.
37
Tabanidae are a diverse group of biting flies, with over 60 known species across 4
genera in northern Ontario (Ringrose et al., 2014; Teskey, 1990). For many of the
species, little is known about their specific habitat preferences, although some idea of
broad preferences can be gleaned at broad scales using range maps. These are species that
are often important pests on large mammals such as caribou, moose and deer (Foil and
Hogsette, 1994). Because of this, it is important to know if there are species preferences
with respect to land cover, including history of forest harvest.
Hybomitra and Chrysopsinae are two of the larger subfamilies within the
Tabanidae. Members of both are predominantly obligate blood-feeding Diptera
(anautogenous species), although some species are facultative blood feeders (the
autogenous species). Members of these sub-familes are found across northern Ontario
(Teskey, 1990). Their last common ancestor was just after the Mesozoic and their
worldwide distribution, primarily in northern climes, has followed the distribution of
mammals (Mackerras, 1954). There is no information on preferred hosts, but the
mouthparts are similar within this group (Teskey, 1990; Thomas, 2011; Thomas and
Marshall, 2009) so it can be inferred that they attack similar host species. The common
history indicates that they should still be found in similarly preferred places. Larger
animals utilize the less dense forests for ease of movement and foraging, although some
animals like woodland caribou (Rangifer tarandus caribou) also utilize dense forest for
short periods of time to avoid biting flies (Bergerud, 1974). If large mammals are using
the younger stands than obligate anautogenous flies should also be there in greater
abundance than elsewhere. A seriation technique was used to examine the seasonal
38
progression of tabanid species and determine if there is habitat partitioning by time of
active year (Brower and Kile, 1988).
In this chapter I test the hypothesis that more recently harvested stands provide
less habitats for tabanids than older or unharvested stands. If this is the case, I predicted
that in recently harvested stands more tabanids, but fewer species, would be found in
comparison to old or unharvested stands.
I also test the hypothesis that competition between tabanids, possibly for blood
meals, would be greater in recently harvested stands compared to old or unharvested
stands in the same region. Kilpatrick and Ives (2003) describe that a slope of less than
two in a Taylor’s Power Law Analysis indicates less variability amongst the rare species
at different sites and that this creates a slope of less than two. It is possible that this can
be explained by increased competition amongst species; but can also be explained by
geographic and stochastic effects.
Materials and Methods
Study area and study sites
In 2011 and 2012, deer fly and horse fly species were sampled at the OMNRF’s
Auden Study site 100 km north of Lake Nipigon in north-central Ontario (Fig. 2.1).
Detailed site descriptions and location and sampling information can be found in Raponi
(2014). A detailed description of sampling is also found in Raponi (2014) and
descriptions of horsefly and deerfly species locations (Diptera: Tabanidae) is found in
Chapter 2 of this thesis. Flies were collected during the ice-free period in both years to
encompass the full active season. Collections were done roughly a week apart, each
39
sample with a total capture effort of 10-20 min sweep netting, systematically varied at
different times of day, to ensure collections at a variety of temperatures.
Environmental information such as latitude and longitude, and stand age was
determined from forest resource inventory maps using OMNRF land classifications. This
includes Ontario Land Classifications (OLC) (OMNR, 2002), and Forest Resource
Inventory (FRI) (Maxie et al., 2010). Temperature was recorded hourly at the site using
an iButton and then the temperature was matched with the time of day at which fly
sampling occurred. iButtons were packaged with duct tape to protect them from the
elements. They were also located 50 m from the stand age and usually marked the
central point of the collection area. They were suspended at a height of 1.7 m. More
information on their usage is described in Raponi (2014).
Analysis
I used an ANCOVA to test the abundance of Tabanidae in the different stands by
age, FRI and OLC categories, with mean temperature, determined by the iButton, at each
site over the sample sessions as the covariate. I used each site as a sample unit, and used
the mean catch per visit at each site, combining catches from 2011 and 2012 as the
response variable. The different treatment variables were stand age, FRI plot category,
and OLC plot category. The individual response variables (means for each site) were total
catch of all Tabanidae, Hybomitra spp., and Chrysops spp., species richness of all
Tabanidae, Hybomitra, and Chrysops. Days with 0 counts were included; 8 sites were not
included, 2 sites (AB02 and AC18) had only 1 sample session and no tabanids were
caught, 6 sites were from lakeshore habitat (AP01, AP02, 3, and AS01, 2, 3) with only 3
sample sessions and of those 1 lakeshore site (AS03) caught only 1 tabanid (Chrysops
40
excitans). All site labels are those assigned by (Raponi, 2014). There were 62 sites used
for the analysis. The minimum number of sessions at a site was 6, with most sites (52)
having at least 14 capture sessions.
Taylor’s power law is lnvariance plotted against the lnmean (Taylor, 1961). For a
community, if there is no interspecific competition using temporal data, then the
theoretical slope of the lnvariance vs lnmean is 2. This is the case if the coefficient of
variation is constant for each species (Kilpatrick and Ives, 2003). This provides a tool to
examine habitat effects on interspecific competition. We expect that for habitat in which
competition is present, that the slope would be significantly less than 2, based on
Kilpatrick and Ives (2003) who stated that when rarer species experience greater
interspecific competition than common species the slope of the line is less than 2.
For each species, we included each day’s catch after the first day an individual
was caught until the last day an individual was caught. We included species with a total
catch of 5 individuals total, or more. Any day in the season during which no Tabanidae
were caught was excluded. In this way, we included all days on which at least one
tabanid was caught of any species, and that occurred between the first and last date for
each species. A chi-square test was done and showed no difference between the overall
season, location and number of specimens caught from 2011 and 2012. As a result we
combined the data for 2011 and 2012 and calculated the mean and variance of the daily
samples for tabanids from each of three harvested stands of different post-harvest ages
(stand ages): 20-35 years, 36-69 years, and at least 70 years which were unharvested.
We then plotted the logevariance against the logemean for each of the forest stand
ages to obtain the slopes. t = (slope – 2)/SEslope These slopes were compared using a
41
dummy variable (Anderson et al., 1982), and were tested against a slope 2 using a 1-
tailed t-test (Kilpatrick and Ives, 2003). This analysis encompasses all species and uses
the species presence and abundance to determine if competition is present.
Seriation was done to look for species clusters of early versus late emergence or
to see if Chrysops were fundamentally different from the other Tabanidae groups,
specifically Hybomitra (other groups were too rarely found to be considered). It has been
used in paleoecology to order taxa based on presence and absence data to create a
timeline of when taxa were present, such that presences form a one-dimensional matrix,
maximizing presences along a diagonal. I used this technique to explore the progression
of species appearances throughout the season and determine if there is any temporal
partitioning of sites amongst species and between sub-families (Brower and Kile, 1988).
The Seriation was constrained, such that only species could be reordered, not dates, and it
was compared against a Monte Carlo simulation. The Monte Carlo simulation was used
to generate 30 random matrices with the same number of occurrences within each taxon
and compare them to the original matrix calculated to see if the experimental data gives
more information than the random matrix. Seriation tests have no assumptions and can
work with any type of data (Brower and Kile, 1988). Seriation series, diversity t-tests and
relative abundance graphs were created using Past 3 software (Hammer et al., 2001).
Results
Seasonality
Figure 3.1 shows that with a couple of exceptions, all common Hybomitra species
(over 40 specimens collected) were found throughout the season at similar abundances.
H. typhus displayed a truncated season in comparison to others, ending much earlier.
42
Chrysops species seemed to have more variability with early/late emergences, but similar
levels of capture during the season (Figure 3.1). C. shermani was an exception where the
species was found at extremely low levels during the season, but spiked mid-July to more
than 20 times its occurrence at other points during the sampling season.
Tabanid abundance and species richness were indistinguishable across the FRI
and the OLC categorized areas. Abundance and richness were different in the three
different stand ages, with sites in the unharvested and mature forest (>70 years) having
the fewest species and lowest abundance (Table 3.1, 3.2), and the sites which were
harvested 35-69 years ago having about 50% more individual tabanids, and about 30%
more species.
The most abundant species, Chrysops excitans, made up 34% of the total catch.
Because it did not meet the assumptions of ANCOVA (slopes were parallel), I compared
C. excitans abundance in the 3 different stands using a Mann Whitney U test, as they did
not meet the requirements of normality. There were more C. excitans caught at sites in
the youngest stands than in either of the other 2 stand types (20-35 vs 36-69, p = 0.01;
20-35 vs >70, p = 0.002; 36-69 vs >70, p = 0.61). The equal slopes found in the
ANCOVA suggests that temperature had no affect on C. excitans. Perhaps at a lower
ambient temperature in the study area the younger stands would have more deerflies.
Overall there were more tabanids caught in younger or older forest stands (Figure
3.2). In general, species were caught most frequently in stands where stands were < 35
years of age and in old stands with time since harvest of > 69 years. The most common of
these species were C. excitans, C. mitis and H. nuda. C. cuclux and H. criddlei are the
two most common species that went against this trend and prefer the mid-age stand. It is
43
possible that this effect follows habitat preferences. In general, all types of forest tree
species were found in each stand age category with the exception of coniferous forests.
Lowland conifer stands were found in all stand age categories, but less so in the 36-69
year stand age; upland conifer stands were entirely missing from this category. C. cuclux
was found mostly in coniferous forest (Fig. 3.2), and mostly found in mid-age stands.
This indicates a possible preference for this habitat. This does not explain H. criddlei’s
numerical dominance in middle-aged stands as it is also found in coniferous, mixed and
deciduous stands (Figure 3.2).
Competition
The linear relationships of the lnmean and lnvariance of species between the stand
ages were: 20-35 years y = 1.96x + 2.59, R² = 0.95; 36-69 years y = 1.63x + 1.61, R² =
0.93; >70 years y = 1.55x + 1.77, R² = 0.96 (Fig. 3.3, Fig. 3.4).
When tested against each other, the slopes of the youngest stands were
significantly different than the slope of the oldest stands, but the other slopes were not
different (Table 3.3).
When tested against an expected slope of 2, the youngest stand was not different,
but the other two stand ages were significantly less than 2 (Table 3.4). If the slope is
caused by competition then this suggests that interspecific competition is minimal in
recently harvested woodlands (20-35 years), at least based on the assumption of the
Taylor’s power law relationship, but that interspecific competition does increase the
aggregation of the rarer species in older stands (harvest histories of 36-69 years and > 70
years). The lowest abundance was also recorded in the mature (>70 years old) stands and
44
it is possible that there was sampling bias since mid-age stands are denser and slightly
harder to collect in. Further research here would be necessary.
Seriation
Seriation was done to examine species clusters of early versus late emerging
species or to see if chrysopidae were fundamentally different from the other Tabanidae
groups, specifically Hybomitra (other groups were too rarely found to be considered).
The years 2011 and 2012 were considered separately because there is often a lot of
variability of species year to year (Hackenberger, Jarić, & Krčmar, 2009). In 2011 the
overall seriation had a value of the Monte Carlo mean of 0.309261 with p=0.009,
meaning that the order of species appearances was significantly different in comparison
to randomly generated matrices. The 2012 seriation result is not significantly different
than randomly generated matrices; with a Monte Carlo mean of 0.273966 and a p <0.25.
Seriations conducted on Hybomitra and Chrysops separately were also non-significant.
Discussion
Most tabanid species were captured in low numbers during the biting fly season;
Chrysops shermani was the exception, with a large spike of individuals caught mid-
season. The known range of C. shermani is predominantly to the south of the Auden
study site (Chapter 2), and, as such, a dramatic spike in the middle of its season when the
temperatures were the highest might have occurred because it is not as well adapted for
the colder temperatures.
Overall it is not possible to differentiate between the landcover types used by
Hybomitra and Chrysops as whole groups. Many of the most common flies, such as C.
excitans, C. mitis, H. pechumani, H. nuda and H. frontalis, were found throughout all the
45
OLC habitats in this region of boreal forest. These were also the same species that
displayed a preference for harvested over unharvested forest. This stand age preference
could have to do with forest density and ability to visualize and host seek (Lehane 2005).
Stand ages under 25 years and over 75 years tend to have similar rates of light
transmittance and those were higher than mid-aged stands (Brown and Parker, 1994).
Some herbaceous plants also show similar preference differences and are also likely
responding to the canopy cover (Ford et al., 2000). C. excitans is anautogenous, and the
apparently most abundant, meaning there is a hungry, obligate, and abundant blood
feeder, which is likely driving the main differences between the stand ages (Anderson
and DeFoliart, 1961). In the harvested forest with less undergrowth Tabanid species, that
are visual predators, would have clearer lines of site. If the species present are highly
anautogenous then it would indicate that they were heavily hostseeking in these
environments.The other explanation is that these areas have higher temperatures which
provides better conditions for biting activity and likelihood of capture (Keenan and
Kimmins, 1993). C. cuclux is found mostly in coniferous forest (Fig. 3.2), and mostly
found in mid-age stands. This indicates a possible preference for this habitat. This does
not explain H. criddlei’s numerical dominance in middle-aged stands as it is also found in
coniferous, mixed and deciduous stands (Figure 3.2). There was substantial yearly
variation between different land types used by various species. The year 2012 was much
wetter year early in the season and had a significant warming event in March (Chapter 2).
This could have affected species choices of habitats. Mikuska et al., (2012) found that
adult horse fly populations were negatively correlated in the year following a significant
warm season and positively correlated to increased rainfall. It would be very interesting
46
to have data from 2013 to see what populations looked like. Also, flies could be shifting
habitat to follow host animals. This may be a result of lower density in younger stands
allowing for better vision to initiate prey capture strategies (McElligott and Galloway,
1991). Less dense stands often occur when an area has been cut and replanted or
selectively cut. If forestry increases in northern Ontario landscapes, this may be
something to investigate more and consider. In areas of lower density and canopy cover
then temperatures are higher and this would likely allow for an increase of tabanid
activity (Keenan and Kimmins, 1993; McElligott and Galloway, 1991). Higher levels of
tabanid activity would likely increase their disturbance of large mammals like woodland
caribou (Bergerud, 1974; Raponi et al., 2018). The Auden site had a history of mostly
clear cutting (Raponi, 2014) so it is less clear what effects selective cuts would have. It is
possible they would immediately act like a mid-aged stand in this study because they
would retain some canopy.
Seriation has been used extensively in archaeology and paleoecology to order
layers of discovery. In theory, this can also be applied to ordering the appearance of
species through a season (Brower and Kile, 1988). Only in 2011 did it appear that species
appeared in any specific order. It is possible that there is a pattern to species emergences
over the summer season, but there are not enough data to test for it (Boyer and Rivault,
2006). This type of partitioning has not been reported in tabanids, but has been
documented in a species of butterfly (Devries et al., 1997) and dragonfly (Alcock, 1987).
More years of cataloguing species might allow for a trend to be shown or, alternatively,
the determination that species emerge randomly each year. For many species captured
there were not many individuals and so this analysis would greatly benefit from increased
47
data (Coddington et al., 2009). Also as noted in Chapter 2, many species had elongated
seasons in comparison to their more southern counterparts. If habitats are changing in the
North then species could be expanding out of their historical habitats and therefore
altering seasonal patterns of established species (Parmesan et al., 2005).
Competition in stands greater than 35 years in age could be occurring as direct
competition as some tabanid larvae prey on other tabanid larvae (Chainey, 1993. Meany
et al., 1976). Competition could also be occuring in adult stages for blood feeding hosts
or some other mechanism (Waage and Davies 1986). The Taylor’s Power Law analysis
shows that in stands over 30 years old there is greater variance amongst rare species. This
could be due to competition, but could also be due to geographic and stochastic factors
(Kilpatrick and Ives 1993).
Many insect species show signs of utilizing different landscapes and having long
seasons without large build-ups in species numbers (Krcmar, 2005; McElligott and
Galloway, 1991; Suh et al., 2015). It would be interesting and valuable to have long-term
monitoring in this area to be able to extend the series of observations over many years. It
appears that the age of stand, likely the tree density of the stand is the most important
factor for determining the location of different Chrysops and autogenous Hybomitra. This
is possibly tied to increased temperatures and lack of canopy cover, but requires more
research to determine the nature of the relationship (Brown and Parker, 1994; Herczeg et
al., 2015; Keenan and Kimmins, 1993) Increased activity could then result in increased
feeding behaviours and competition for food. We have shown a strong preference for
younger stands by most Tabanid species, but it would be interesting to compare this
research to a site with similar harvest history, but located in a different climate zone. This
48
would allow us to determine if temperature or light has a larger influence over tabanid
behaviour.
49
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53
2011 2012
Scale Bar
(0-50 flies
caught/day
demarcated
by 10)
Hybomitra
astuta
Chrysops
indus
H. zonalis
C. frigidus
54
H. lurida
C. venus
H. criddlei
H. trepida
H. typhus
Figure 3.1 a The relative abundance of tabanid species (with under 100 specimens) for
2011 and 2012. The x-axis represents days from first observations taken to last of all
species. The y-axis represents numbers of individuals observed. On the y-axis, zero
observations are is recorded in the middle of the vertical axis and any observations is
drawn both up and down vertically, to help visualize population fluctuations. The scale
bar in the first row shows a range of relative abundances from 0-50.
55
Scale Bar (0-
100) flies
caught/session
demarcated
by 25
H. epistates
C. ater
C. shermani
H. affinis
C. carbonarius
25 50 75 100
56
H.
lasiopthalma
H. illota
H. frosti
C. dawsoni
C. cuclux
H. frontalis
57
H. nuda
H. pechumani
C. mitis
Figure 3.1b The relative abundance of tabanid species with 100-1000 specimens for 2011
and 2012. The x-axis represents days from first observations taken to last of all species.
The y-axis represents numbers of individuals observed. On the y-axis, zero observations
are recorded in the middle of the vertical axis and any observations is drawn both up and
down vertically from thereout. This was done to help visualize population fluctuations.
The scale bar in the first row shows a range of relative abundances from 0-100.
58
2011 2012
Scale Bar
(0-400 flies
caught/session)
demarcated by
100s
C. excitans
Figure 3.1c The relative abundance of C. excitans for 2011 and 2012. The x-axis
represents days from first observations taken to last of all species. The y-axis represents
numbers of individuals observed. On the y-axis, zero observations are recorded in the
middle of the vertical axis and any observations is drawn both up and down vertically
from thereout. This was done to help visualize population fluctuations. The scale bar in
the first row shows a range of relative abundances from 0-400.
100
200
300
400
59
Figure 3.2: Stand age preferences by the abundance of species (with over 75 specimens
combined for 2011 and 2012).
60
Figure 3.3 Plot of ln(mean) vs ln(variance) of daily trap catches of tabanid species for
three stand ages: 20-35 years (open circles), 36-69 years (black diamonds) and > 70 years
(crosses). The slope of the heavy line (open circles, youngest stand) does not differ from
a slope of 2.
y = 1.96x + 2.59, R² = 0.9520-35 years, open circles
y = 1.63x + 1.61, R² = 0.9336-69 years, diamonds
y = 1.55x + 1.77, R² = 0.96>70 years, crosses
-4
-3
-2
-1
0
1
2
3
4
5
6
-4 -3 -2 -1 0 1 2 3
lnva
ria
nce
ln mean
61
Figure 3.4 Plot of lnmean vs lnvariance of daily trap catches of Chrysops spp (left) and Hybomitra spp (right) in
regions of three stand ages: 20-35 years (open circles), 36-69 years (black diamonds) and > 70 years (crosses) post harvest.
The slope of the heavy line (open circles, youngest stand) does not differ from a slope of 2 for Chrysops.
-4
-3
-2
-1
0
1
2
3
4
5
6
-4 -3 -2 -1 0 1 2 3
lnm
ean
ln variance
-4
-3
-2
-1
0
1
2
3
4
5
6
-4 -3 -2 -1 0 1 2 3ln
mean
ln variance
Hybomitra Chrysops
years 20 – 35 y = 1.97x + 2.39 R² = 0.97 36 – 69 y = 1.79x + 1.88 R² = 0.96 > 70 y = 1.59x + 1.98 R² = 0.98
years 20 – 35 y = 1.50x + 2.84 R² = 0.92 36 – 69 y = 1.38x + 1.22 R² = 0.93 > 70 y = 1.54x + 1.62
R² = 0.96
ln mean mean
ln mean
ln v
ariance
62
Table 3.1. Test results for differences in richness and abundance of tabanids in harvested
versus unharvested stands of ANCOVA, using the mean temperature at each site as the
covariate. There were 62 sites divided into 3 stand ages. Ages (years) of harvested and
unharvested stands are noted.
Stand type adjusted meansa
Harvested Unharvested
Test F(2, 58) P (20-35 yrs) (36-69 yrs) (≥70 yrs)
Tabanidae abundance 3.376 0.041 10.63 13.36 8.56
Hybomitra abundance 0.960 0.389 3.83 4.64 3.70
Chrysops abundance 3.468 0.038 6.80 8.72 4.86
Tabanidae species richness 5.407 0.007 2.58 3.09 2.31
Hybomitra species richness 3.738 0.030 1.35 1.71 1.32
Chrysops species richness 4.042 0.023 1.22 1.37 0.97
aUnadjusted means are in Table 3. 2.
63
Table 3.2. Summary of mean abundance and richness of Tabanidae, Hybomitra, and
Chrysops.
Stand age N Abundance
Species richness
Mean 95% C.I.
Mean 95% C.I.
Tabanidae
20-35 yrs 17 11.245 8.844 13.647
2.665 2.335 2.994
36-69 yrs 14 12.039 6.871 17.207
2.907 2.271 3.543
> 70 yrs 31 8.822 6.502 11.142
2.346 2.033 2.659
Hybomitra
20-35 yrs 17 4.013 2.958 5.068
1.395 1.153 1.638
36-69 yrs 14 4.246 3.237 5.254
1.620 1.342 1.899
> 70 yrs 31 3.781 2.813 4.749
1.338 1.146 1.531
Chrysops
20-35 yrs 17 7.233 5.393 9.072
1.262 1.036 1.488
36-69 yrs 14 7.793 3.351 12.235
1.277 0.845 1.710
> 70 yrs 31 5.041 3.397 6.686 0.988 0.839 1.137
64
Table 3.3 Comparison of ln(variance)/ln(mean) slopes in Taylor’s Power Law using a
dummy*X variable.
test of slopes t Stat P-value d.f.
20-35 yrs vs 36-69 yrs 1.47 0.147 68
20-35 yrs vs ≥ 70 yrs 2.18 0.033 68
36-69 yrs vs ≥ 70 yrs 1.96 0.053 68
65
Table 3.4. Slopes of ln(variance/ln(mean) for three different stand ages tested against a
slope of 2 using a t-test. Significant p values are for slopes that are less than 2; bold p-
values are those not significantly less than 2.
All species
Stand age slope SE slope t df p y-intercept R²
20-35 years 1.96 0.079 0.50 34 0.31 2.59 0.95
36-69 years 1.63 0.076 4.84 34 1.4E-05 1.61 0.93
> 69 years 1.55 0.052 8.52 34 2.9E-10 1.77 0.96
Chrysops
20-35 years 1.97 0.086 0.38 16 0.36 2.39 0.97
36-69 years 1.79 0.098 2.19 16 0.02 1.88 0.96
> 69 years 1.59 0.066 6.14 16 7.1E-06 1.98 0.98
Hybomitra
20-35 years 1.50 0.111 4.51 18 0.00013 2.84 0.92
36-69 years 1.38 0.094 6.62 18 1.6E-06 1.22 0.93
> 69 years 1.54 0.082 5.63 18 1.2E-05 1.62 0.96
66
Chapter 4: General Conclusion
The first objective of my thesis was to examine species abundance, distributions
and diversity of tabanids in an understudied geographic area in the Near North of the
Province of Ontario. This work is important because it provides baseline data for further
investigations, particularly as there is increased northern development and a changing
climate. The second objective of my thesis was to test whether there was an effect of
stand age and forest cover type on the spatial and temporal distribution of the Tabanidae
in my study site.
For the first and most important objective, I have increased the baseline
distributional knowledge of Tabanidae. In the second chapter, I presented my collections
of 8928 tabanids. From these collections, I extended the known distribution of 18
Tabanidae species, 8 northward and 10 range infills, many of these in conjunction with
the additions by Ringrose et al. (2014) to the northern Ontario distributions of tabanids.
Chrysops shermani in particular had its range extended approximately 450 km north;
over 350 individuals were found over 2 years, indicating that this is likely a breeding
population and not merely a transfer on a weather front. This finding is important because
it indicates that there is still much to be learned from studying this region. This small
study added to the body of knowledge of tabanids in northern Ontario. Existing
distribution records are based on a few earlier studies (Teskey 1990, Thomas 2009,
Thomas and Marshall 2011, Ringrose 2014). While extensive, these are nonetheless
limited by the remoteness and the scale of sampling in northern Ontario. More sampling
would likely lead to further gains in species information such as range and season.
67
The increased land use and habitat changes due to forestry, mineral extraction,
population increase and climatic effects argues for an urgency in increasing knowledge of
species distributions in northern Ontario (Able, 2016). The area cannot be considered
pristine, but an evaluation of current distributions does provide us with a baseline for
assessing future change. Tabanids are primarily blood-feeding insects that therefore rely
heavily on other species as hosts. Their preferences of host are often specific to large
mammals and birds; they are therefore affected by the type of habitat surrounding them,
including forest cover because these features of the environment also affect the locations
of their hosts. Forest harvesting changes the density of brush and host/prey dynamics of
species in the area (Teskey, 1990; Thomas, 2011; Thomas and Marshall, 2009). Tabanids
also have aquatic larvae, and are therefore susceptible to changes in both aquatic and
terrestrial habitats (Teskey, 1990). Their annual generation times, which are rapid in
comparison to many other species, including large mammals, mean that changes to
populations occur rapidly and can be indicative of larger change. While there are not
studies using Tabanidae to monitor environmental change, insects in general provide an
ideal group of organisms for this purpose (Devictor et al., 2012). More knowledge can
only help in the task of monitoring change, which has a sense of increased urgency as
climate change effects are becoming more commonly felt (Hughes et al., 2003; Sanders,
2014).
The second objective was to find evidence of habitat specificity of species or
groups of tabanids. In general no differences could be seen in the distribution of biting
tabanids in this study, between forest stand types or in their temporal pattern of
distributions within the summer season. The scale of the study may have been too fine to
68
elucidate any differences. In general harvested stands, those under 60 years of age, were
found to host more individuals, and had over 30% greater richness. Specifically the most
common tabanid, Chrysops excitans, an aggressive host seeker, preferred younger stands.
This could indicate a link between forest management strategies and responses of
particularly large mammals to this type of change (Simberloff, 1988). Rangifer tarandus
caribou, woodland caribou, is a boreal species whose populations are threatened. Raponi
et al. (2018) discerned that this species show lowered activity during periods of high
densities of active tabanids. This conceivably could cause weight loss as it reduces
foraging time. If this connection between forest harvesting and caribou pest populations
can be strengthened, it may indicate that woodland caribou are facing increased stress
from increased pest numbers in younger stands of wood (Hins et al., 2009; Nadeau et al.,
2016; Raponi et al., 2018). Therefore even if food and other habitat requirements are
available, caribou may still not be able to fully access these resources if they are
displaying host avoidance behaviours because of the tabanids. It would add another
aspect to planning of forestry management. Cooler, older stands reduce tabanid activity
and may provide a possible refugium from tabanid pests for large mammals.
In general, my thesis provided information to build baseline data of species
richness, relative abundance and distribution of an important taxon of insects. As this is
the fundamental unit of biogeography it will allow for informed future tracking and
provide information to help inform forestry management, species at risk and climate
change monitoring.
The difficulties of lack of sampling in northern Ontario has been mentioned a
number of times throughout this thesis. Future research should focus on sampling in new
69
area of northern Ontario in order to expand our knowledge of species ranges. It would
also be useful to sample more intensively at a small site using sweep netting and more
passive methods of capture. This would allow for a greater diversity of species caught
and a more detailed picture of species usage of an area over a season. If this were done
then competition between anautogenous species could be examined. It would also be
interesting to compare forest stands of similar ages, but different weather to try and
determine if tabanid activity is linked to canopy cover or temperature. Developing the
understanding of competition by tabanid species in stands of different ages. Forest stands
in this study area were also very small. Larger stands, may show more differentiation of
species usage. All of this research will add to the relatively sparse knowledge of tabanids
in northern Ontario and build upon the baseline knowledge acquired in this thesis.
70
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Appendix
Table A.1: List of Study sites exclusive to one year of sampling (Raponi 2014).
2011 2012
AB02
AB06
AC03
AC18
AC25
AL28
AC24
AP01
AP02
AP03
AS01
AS02
AS03
OL01
OL02
OL03
OL04
TL01
