POLLINATION BIOLOGY OF DARLINGTONIA CALIFORNICA, THE

POLLINATION BIOLOGY OF DARLINGTONIA CALIFORNICA, THE CALIFORNIA

PITCHER PLANT

by

George A. Meindl

A Thesis

Presented to

The Faculty of Humboldt State University

In Partial Fulfillment

Of the Requirements for the Degree

Master of Arts

In Natural Resources: Biology

December 2009

POLLINATION BIOLOGY OF DARLINGTONIA CALIFORNICA, THE CALIFORNIA

PITCHER PLANT

by

George A. Meindl

We certify that we have read this study and that it conforms to acceptable standards of scholarly presentation and is fully acceptable, in scope and quality, as a thesis for the degree of Master of Arts. Michael R. Mesler, Major Professor Date John O. Reiss, Committee Member Date Erik S. Jules, Committee Member Date Terry W. Henkel, Committee Member Date Michael R. Mesler, Graduate Coordinator Date John Lyon, Dean Research & Graduate Studies Date

iii

ABSTRACT

Pollination biology of Darlingtonia californica, the California pitcher plant

George A. Meindl

The flowers of the California pitcher plant, Darlingtonia californica, are unusual

and have been the subject of much speculation. Despite the efforts of several workers,

the pollination ecology of this plant, including the identities of pollinators, remains

enigmatic. Along with determining visitation frequency, this study sought to describe the

relative contributions of two documented floral visitors, bees and spiders. Fruit and seed

production by emasculated flowers were used to estimate levels of cross-pollination in

natural populations of D. californica. Under the assumption that bees predominantly act

as cross-pollinators and spiders as self-pollinators, this treatment was used to infer which

organisms were responsible for pollen transfer. Levels of pollen-limitation were also

assessed at five study sites in northwest California. In order to identify floral visitors,

extensive pollinator surveys were conducted. A generalist solitary bee, Andrena

nigrihirta, was found to visit D. californica flowers near Scott Mountain and Mt. Eddy,

CA. Despite relatively low visitation rates, individual flowers at all study sites were

expected to receive at least one visit by A. nigrihirta. Other regular floral visitors

included thrips and several species of spiders. Fruit and seed production by emasculated

flowers indicated the occurrence of cross-pollination. Unmanipulated flowers produced

more fruits and seeds, on average, compared to emasculated blooms, suggesting that self-

pollination contributes to D. californica reproductive success as well. While bees were

iv

likely responsible for the majority of cross-pollination, both bees and spiders contributed

to autogamous pollen transfer. Following observations of floral visits by A. nigrihirta, it

was possible to interpret the functional morphology of D. californica’s flowers. The

shape of D. californica’s ovary and petals promote stigma contact both when pollinators

enter and exit a flower, contrary to previous thought. This system provides an excellent

example of the importance of identifying and observing pollinators in order to truly

understand the functional significance of a plant’s floral morphology.

v

ACKNOWLEDGMENTS

First and foremost, I would like to thank my adviser, Dr. Michael Mesler, whose

combination of patience and enthusiasm made this work possible. I am also grateful to

the professors who served on my committee: Dr. Erik Jules, Dr. Terry Henkel, and Dr.

John Reiss. Many thanks to Dave Franklin, whose general knowledge contributed much

to this thesis. Tim Buonaccorsi and Sasan Hariri-Moghadam were invaluable as research

assistants. Without their help I might still be counting Darlingtonia seeds, among other

tasks. Figures 2 and 3 were illustrated by Sasan Hariri-Moghadam. Will Goldenberg

assisted with video editing. As always, thank you to my family and friends.

vi

TABLE OF CONTENTS

Page

ABSTRACT ....................................................................................................................... iii

ACKNOWLEDGMENTS .................................................................................................. v

LIST OF TABLES ............................................................................................................ vii

INTRODUCTION .............................................................................................................. 1

METHODS AND MATERIALS ........................................................................................ 5

Study Species .......................................................................................................... 5

Study Sites .............................................................................................................. 6

Pollinator Surveys ................................................................................................... 9

Analysis of Pollen Loads ...................................................................................... 10

Pollination Treatments .......................................................................................... 11

Plant Community Context .................................................................................... 12

Statistical Analyses ............................................................................................... 13

RESULTS ......................................................................................................................... 14

Flower Visitors...................................................................................................... 14

Floral Mechanism/ Pollinator Behavior ................................................................ 18

Pollination Treatments .......................................................................................... 23

Plant/ Insect Community Context ......................................................................... 24

DISCUSSION ................................................................................................................... 29

Future Research .................................................................................................... 33

LITERATURE CITED ..................................................................................................... 35

vii

LIST OF TABLES

Table Page 1 Elevation and geographic coordinates of five study sites. ...................................... 7

2 Observed visits to Darlingtonia californica flowers. Aside from the one visit recorded by a European honeybee (Apis mellifera), Andrena nigrihirta was the only bee observed to visit the flowers. Numbers in parentheses indicate the number of visits to different flowers observed during a given time period(s). ..... 15

3 Floral visitation rates. The mean number of visits a flower was expected to receive per hour and over its lifetime is presented for each study site. Standard error values for mean visits/hour are given in parentheses for each study site. .... 16

4 Duration of visits to Darlingtonia californica flowers by Andrena nigrihirta. Average visit duration was 2 minutes 8 seconds (SE=12 seconds ....................... 17

5 The percentage of examined flowers at each study site that contained one or more of the following: thrips, spiders, and spider webs (either inside or outside the flower). A total of 1125 flowers were individually examined (150 at CL, 225 at SM1, 250 at SM2, 250 at N17, and 250 at DF). “Evidence of Spider” column represents the percentage of examined flowers at each site that had a spider and/or webbing present. Only 3/1125 (0.27%) flowers contained one or more fungus gnats. ..................................................................................................................... 22

6 The percentage of ground covered by Darlingtonia californica and co-flowering plant species. The total percentage of ground covered by angiosperms both within and outside (50m) the seeps are shown in the first two columns. The percentage of ground covered by Darlingtonia californica within the seeps is also presented. .............................................................................................................. 26

7 Pollinators collected at or near study sites. Order and family is presented for all pollinators (and genus for Hymenopterans). Numbers in parentheses indicate the number of individual pollinators collected from each group ................................ 28

viii

LIST OF FIGURES

Figure Page

1 Map of study area. Triangles represent the five study sites. SM1, SM2, and CL were near the summit of Scott Mountain, while N17 and DF were near Mt. Eddy. The gray line separates Siskiyou County and Trinity County. .................... 8

2 Step by step foraging behavior of A. nigrihirta on a D. californica flower. The bee initially lands on the petals below the windows (a-c) and then enters a window and walks across stigmatic surfaces (d,e). The bee then utilizes the convex portion of one of the five petals to walk onto the ovary and up to collect pollen (f-i). Following pollen collection, the bee uses a petal convexity as before to walk down the ovary, across the stigmas again, and then out one of the windows (j-n). The flower is shown in d-m with one petal removed and half of the two lateral petals removed. F and k show the bee using the convex portion of the petal, which allows the bee to access the stamens. ......................................... 20

3 Interior view of a D. californica flower with the lower portion of petals removed. Arrows highlight the distance between the petals and the ovary both immediately above a window (shorter arrow) and in between two adjacent windows (larger arrow). More space is provided for A. nigrihirta in between the windows than above them, which encourages the bee to enter a window and then walk across the stigmatic surfaces. The bee then utilizes the convex portion of the petal opposite the window it entered en route to the flower’s stamens. ....................................... 21

4 Fruit and seed production by three treatment groups (emasculated, unmanipulated, and hand-pollinated flowers) at each study site. Top: Fruit set (%) of three treatment groups at each field site. Emasculated flowers produced significantly fewer fruits than unmanipulated flowers. No significant difference was found between fruit production of unmanipulated vs. hand-pollinated flowers (χ2=3.50, p=0.0615). Bottom: Average number of seeds produced per capsule from three treatment groups at each field site. Different letters above bars indicate group means are significantly different. .......................................................................... 27

ix

LIST OF APPENDICES

Appendix Page

A Plant species in coincident bloom with Darlingtonia californica near Scott Mountain and Mt. Eddy, CA................................................................................. 39

B Results of percent ground cover analyses. Separate tables are presented for ground cover within versus outside seeps at all five study sites. .......................... 43

1

INTRODUCTION

The study of interactions between plants and their pollinators can provide

adaptive explanations for flower morphology (Fenster et al. 2004, Vogel 2006, Hu et al.

2008, Pauw et al. 2008, Crepet and Niklas 2009). Unless a plant’s effective pollinator is

determined, however, the adaptive significance of individual floral traits cannot be fully

understood. The flowers of the California pitcher plant, Darlingtonia californica, are

unusual and have been the subject of much speculation (Debuhr 1973, Schnell 1976).

For example, some have theorized that D. californica’s bell-shaped ovary serves to limit

self-pollination (Schnell 1976), but direct observations of flower handling by floral

visitors are lacking. Despite the efforts of several workers, the pollination ecology of this

plant, including the identities of pollinators, remains enigmatic (Austin 1875-1877, Elder

1997, Nyoka and Ferguson 1999, Nyoka 2000). Until D. californica’s pollinators are

identified and observed, we will not be in a position to interpret the functional

morphology of the flowers in a meaningful way.

Though pollinator sightings have been rare, fruit set in natural populations of D.

californica has been shown to be quite high, indicating an active pollinator community

since the flowers do not routinely self-pollinate without an animal pollen vector (Elder

1997, Nyoka 2000). Based on appearances, the flowers of D. californica seem adapted

for pollination by bees. They are large, showy, sweetly fragrant, and produce abundant

pollen (Debuhr 1973, Nyoka and Ferguson 1999) – all features commonly associated

with mellitophily. In addition, D. californica’s closest relatives, Sarracenia and

2

Heliamphora spp., are pollinated predominantly by bumble bees (Thomas and Cameron

1986, Renner 1989, Ne’eman et. al. 2006), suggesting that bee pollination may be

primitive for Sarraceniaceae. Nevertheless, bees have seldom been observed as visitors

to D. californica flowers (Austin 1875-1877, Elder 1997, Nyoka and Ferguson 1999,

Nyoka 2000). Spiders, in contrast, are relatively commonly observed on the flowers.

While pollination is generally not a service provided by spiders, recent studies suggest

that they may be significant pollinators of D. californica flowers (Nyoka and Ferguson

1999, Nyoka 2000). This interpretation seems problematic considering D. californica’s

floral morphology, but it is possible that spiders are currently responsible for the majority

of pollination even if flower morphology is the result of past selective pressures applied

by bees. If D. californica is pollinated exclusively by spiders, this system would provide

another example where floral morphology does not necessarily reflect contemporary

pollinator type (Fenster et al. 2004, Zhang et al. 2005, Valdivia and Niemeyer 2006).

Certain spider taxa, including members of the families Clubionidae, Salticidae,

and Theridiidae, use the flowers of D. californica as hunting grounds and may act as

pollen vectors as they move within flowers constructing webs and stalking prey (Nyoka

and Ferguson 1999, Nyoka 2000). By experimentally introducing spiders to bagged

flowers, Nyoka (2000) showed that spiders can cause autogamous pollen transfer. She

also observed pollen-dusted webbing constructed between adjacent flowers, indicating

the potential for xenogamous pollen transfer by spiders as well (Susan Nyoka, personal

communication).

3

The evidence for spider pollination, however, is far from conclusive. While

Nyoka (2000) demonstrated that spiders can potentially act as pollen vectors, fruit set by

open-pollinated flowers (96%, n=25) was much higher than that resulting from spider

introductions (41%, n=22) (Nyoka 2000). Of the flowers that matured fruits, far fewer

seeds were produced by spider-pollinated flowers (average=32 seeds/capsule) than open-

pollinated flowers (average=673 seeds/capsule) (Nyoka 2000). The discrepancy in

reproductive success between spider introduced and open-pollinated flowers suggests that

another, more effective pollinator is active among D. californica blooms. Though some

spiders supplement their diets with nectar and/or pollen (Smith and Mommsen 1984,

Vogelei and Greissl 1989), ultimately they rely on insect prey to sustain themselves. If

spiders feed on potentially effective pollinators, they may reduce seed production more

than they contribute to it.

This study sought to address the following questions regarding D. californica’s

reproductive biology at five study sites in northern California: (1) Do both bees and

spiders contribute to overall reproductive success? (2) Are past interpretations of the

functional morphology of floral traits correct, i.e., does the shape of D. californica’s

ovary limit self-pollination as has been suggested (Schnell 1976)? (3) Is natural

pollination sufficient for effective fruit and seed set, or are plants experiencing pollen-

limitation? (4) Do cross-pollination and self-pollination each contribute to natural

pollination? In order to identify floral visitors, extensive pollinator surveys were

conducted. Once a key floral visitor was identified detailed observations of its flower-

handling behavior were made to elucidate whether the shape of D. californica’s flowers

4

serves to limit self-pollination. Levels of pollen-limitation were assessed by comparing

fruit and seed production by hand-pollinated flowers with fruit and seed production by

unmanipulated flowers. The performance of emasculated flowers was used to estimate

levels of cross-pollination.

5

METHODS AND MATERIALS

Study Species

Darlingtonia californica is endemic to western Oregon and northern California,

and has a patchy distribution across its range due to its unique habitat requirements. The

species is considered an indicator of serpentine soil and is restricted to perennially wet

seeps (Whittaker 1954, Schnell 1976, Juniper et al. 1989). A long-lived perennial, D.

californica annually produces rosettes of carnivorous leaves from a creeping rhizome.

Plants often occur in dense patches, which are likely the result of clonal spread by

rhizomes and stolons (Schnell 1976).

The solitary flowers begin as upright buds, but become pendant when mature

(Debuhr 1973). The flower-bearing scape generally ranges from 40-60 cm, but may

grow as tall as 90 cm (Debuhr 1973). On average, each scape bears nine bracts, all of

which have nectar secreting glands (Macfarland 1908). Unlike some confamilial

Sarracenia spp. (Ne’eman et al. 2006), the flowers of D. californica produce no nectar

(Debuhr 1973). Abundant pollen is the only likely reward for pollinators, though a sugar-

rich stigmatic exudate may also attract visitors (Nyoka 2000). Five lanceolate-ovate,

yellow-green sepals hang loosely around five crimson petals. The five petals almost

completely enclose the reproductive whorls, except for windows formed by notches in

adjacent petals, which allow access to the flower’s interior. The windows are level with

the five stigmatic lobes, a feature that may promote the deposition of outcrossed pollen as

6

pollinators initially enter a flower. Twelve-fifteen stamens are located at the base of the

ovary. The bell-shaped ovary is flared towards the stigmas, which has been postulated to

function to guide pollinators away from the stigmas as they exit a flower and thus limit

self-pollination (Schnell 1976). Flowers mature into upright capsules capable of

producing around 2000 seeds (Debuhr 1973). The flowers of D. californica are self-

compatible, but do not self-pollinate autonomously (Elder 1997, Nyoka 2000).

Study Sites

Five seeps located near Scott Mountain and Mt. Eddy, CA were used in this study

(Figure 1, Table 1). The five study sites will hereafter be referred to as SM1, SM2, CL,

N17, and DF. Distance between sites ranged from ~0.1 to 14.5 km. Near the border of

Trinity and Siskiyou Counties, this portion of the Klamath Bioregion represents the

center of D. californica’s range (Debuhr 1973). Common woody associates adjacent to

seeps include Jeffrey pine (Pinus jeffreyi), huckleberry oak (Quercus vaccinifolia),

western azalea (Rhododendron occidentale), white fir (Abies concolor), red fir (Abies

magnifica) and incense cedar (Calocedrus decurrens). Within the seeps, common

associates include white rushlily (Hastingsia alba), California bog asphodel (Narthecium

californicum), Sierra shootingstar (Dodecatheon jeffreyi), marsh marigold (Caltha

leptosepala var. biflora), and Bigelow’s sneezeweed (Helenium bigelovii). Flowering

occurred at all study populations between June 12, 2008 and June 22, 2008, except for

CL where flowering started earlier (June 6, 2008). Study sites were chosen based on

accessibility and population size.

7

Table 1. Elevation and geographic coordinates of five study sites.

Site Elevation Spatial Coordinates

SM1 1635 m. 41° 16’ 25.00” N; 122° 41’ 58.21” W

SM2 1630 m. 41° 16’ 38.57” N; 122° 41’ 57.54” W

CL 1693 m. 41° 18’ 01.49” N; 122° 40’ 59.90” W

N17 1945 m. 41° 20‘ 08.05“ N; 122° 31‘ 41.53“ W

DF 2001 m. 41° 20’ 09.13” N; 122° 31‘ 11.39“ W

8

Figure 1. Map of study area. Triangles represent the five study sites. SM1, SM2,

and CL were near the summit of Scott Mountain, while N17 and DF were near Mt. Eddy. The gray line separates Siskiyou County and Trinity County.

9

Pollinator Surveys

Three observation points were established in each seep in order to monitor

pollinator activity. At these points a series of timed (15 minute) surveys were conducted,

focusing on 13-17 flowers. I sat quietly and motionless while observing the flowers in an

effort not to disturb active pollinators or alter their behavior. Ten 15-minute surveys (2.5

hours total) were conducted during each trip to a field site. Most surveys were made

between 10:00 a.m. and 6:00 p.m., but several were made in the early morning and late

evening. In total, 57.5 hours were devoted to surveys between June 6, 2008 and July 3,

2008. A subset of pollinator visits was timed and filmed with a digital camera. Timing

began when a pollinator entered one of the windows, and ended when it exited a window.

Videos were used to provide detailed accounts of insect visitation.

Mean flower visitation rates (visits/flower/hour) were calculated for each study

site. The expected number of visits a flower received over its lifetime was estimated by

multiplying the flowering period (in days) by the number of hours in a day pollinators

were active (six hrs.) by the visits/hour calculated for each site. D. californica pollinators

were considered to be active for six hours a day because all visits occurred between 10:30

a.m. and 4:30 p.m. Flower lifespan was determined by monitoring the development of 30

tagged buds at each study site. The flowers were synchronously bisexual (i.e., stigma

receptivity and anther dehiscence occurred simultaneously). Flowers were deemed

mature when stigmas were receptive (exudates present) and anthers were dehiscing

10

pollen and were considered past maturity when stigmas withered and ovaries began to

swell and turn upright. By July 1, 2008, flowers were developing fruits at all sites.

Tagged flowers were considered receptive at CL between June 6, 2008 and June 22, 2008

(17 days), while tagged flowers were receptive at SM1, SM2, N17, and DF between June

12, 2008 and June 22, 2008 (11 days). Visitation rates were calculated for each site

independently.

Following each 15 minute census period, five flowers were carefully examined by

spreading apart the sepals and petals to check for animals already present within the

flowers. A total of 1125 flowers were inspected in this way for spiders, spider webs

(either inside or outside the flower), fungus gnats, and thrips. Insects were captured by

aerial netting or by hand, and identified.

Pollinator surveys were also conducted on concurrently flowering plant species.

Approximately 10 hours were devoted to collecting and describing the local pollinator

community. Surveys were conducted by walking in and around seeps and stopping

periodically to observe and collect pollinators on concurrently blooming plants.

Analysis of Pollen Loads

Each insect collected during surveys that carried a visible pollen load was

systematically dabbed with a small cube of glycerin jelly containing basic fuchsin stain

(Kearns and Inouye 1993). Following pollen removal, the jelly was placed on a

microscope slide, melted and covered with a cover slip for analysis. Pollen grains were

identified by comparing them to a series of slides prepared from flowers at each site.

11

Pollination Treatments

In order to test the assumption that fruit and seed set in natural populations of D.

californica are high, 30 unmanipulated flowers at each site were monitored through their

development. Because flowers do not autonomously self-pollinate (Elder 1997, Nyoka

2000), pollinator activity can be estimated based on the reproductive success of

unmanipulated flowers. Fruit and seed set resulting from unmanipulated flowers were

also compared against that of an equal number of hand-pollinated flowers to determine if

plants were experiencing pollen-limitation. If there is no difference in fruit and seed set

between these two treatment groups then we can conclude that natural pollination is

sufficient, i.e., plants were not pollen-limited. Following the appearance of stigmatic

exudates, supplemental pollen was applied twice (separated by one week) to 30 flowers at

each site by rubbing two-three mature anthers directly against stigmatic surfaces. Pollen

used for hand-pollinations was collected from flowers at least five m away in the same

population.

To gauge the relative importance of spiders versus bees as pollinators, 30 flowers

in each seep were emasculated prior to maturity. Bees, which tend to visit multiple

flowers on any given foraging bout, would likely promote xenogamous pollen transfer for

D. californica (though depending on their foraging behavior and flower handling, bees

may cause some level of autogamy as well). If past interpretations of the functional

morphology of flowers hold true (i.e., if ovary shape limits insect mediated self-

pollination) then bees may contribute minimally to autogamous pollen transfer. Spiders,

however, tend to remain resident within single flowers for longer periods of time and

12

would likely contribute primarily to autogamous pollen transfer. Any seeds produced in

the emasculated treatment group must be the result of cross-pollination, thus levels of

cross-pollination and self-pollination can be estimated by comparing the seed set of the

emasculated flowers with the seed set of unmanipulated flowers. Under the assumption

that bees would act mainly as cross-pollinators and spiders as self-pollinators, this

comparison was also intended to show what organisms were likely responsible for pollen

transfer.

A total of 450 flowers were used for fruit and seed set experiments, with 150

flowers in each of the three treatments: hand-pollinated, emasculated, and unmanipulated.

These treatments were spread equally across the five study sites (i.e., 90 flowers at each

site in three treatment groups of 30). Once fruit maturation began, all treatment flowers

were bagged with Reemay® to ensure seeds were not lost when capsules began to

dehisce. This proved to be an unnecessary precaution since all fruits were collected prior

to dehiscence. Fruit set was determined for each site, as well as the number of seeds

produced by each capsule.

Plant Community Context

To characterize floral resources available to pollinators that were active during the

blooming period of D. californica, all concurrently blooming plant species were

identified in and around the field sites (within 150 m). Due to the close proximity of

SM1 and SM2, all coincidentally blooming plants discovered at either site were

13

considered to be present at both sites. In order to quantify floral resources provided by

these plants, percent ground cover was determined in eight m x eight m plots both within

the seeps, as well as 50 m outside each seep in the surrounding uplands. Five eight m

transects, separated by two m from each other, were laid down to establish the plots.

Plots within the seeps were chosen haphazardly, while the corresponding upland plots

were placed 50 m outside each seep at a right angle to the center of the plot within the

seep. Within each eight m x eight m plot, 25 0.5 m x 0.5 m subplots were used to

describe percent ground cover of all coincidentally blooming species. A frame

constructed of PVC pipe with a wire grid (100 squares) was laid over the vegetation and

used to estimate ground cover on a scale of 0-100% for each species in bloom.

Statistical Analyses

Log linear analysis was used to compare the fruit set of the three experimental

treatment groups, with treatment, site and the interaction term included in the model. A

two-way ANOVA was used to compare seed set across all sites, with treatment and site

as the independent variables. Due to a significant interaction term from the two-way

ANOVA (p=0.041), separate one-way ANOVAs were run for each site independently

using treatment as the independent variable. A multiple comparison of means was also

completed, using a Bonferroni adjustment. A Kruskal-Wallis one-way analysis of

variance was used to compare visitation rates across all sites. All statistical analyses

were performed using NCSS (Hintze 2004).

14

RESULTS

Flower Visitors

Over 57.5 hours of surveys, only 38 visits by flying pollinators were observed: 37

by a solitary bee, Andrena nigrihirta, and one by a European honeybee (Apis mellifera)

(Table 2). Estimated visit rates varied from 0.077 (SE=0.025) visits/flower/hour at N17

to 0.016 (SE=0.029) visits/flower/hour at CL, which correspond to 5.08 and 1.60

visits/flower’s lifetime, respectively (Table 3). Visit rates, however, were not

significantly different across all five sites (Kruskal-Wallis χ2=5.72, p=0.22). A. nigrihirta

stayed in individual flowers for extended time periods. Out of 14 timed visits, A.

nigrihirta foraged on a single D. californica flower for an average of approximately two

minutes and eight seconds (128 seconds +/- 12 seconds; Table 4). Eight individuals were

collected immediately following visits, and all carried D. californica pollen on their

scopae. Of these, six carried D. californica pollen exclusively while two carried

heterospecific pollen as well (Asteraceae). A. nigrihirta was the only pollinator collected

found to carry the pollen of D. californica.

Spiders were common on flowers at all five study sites, and were active at all

hours of the day. Whereas 26.2% of all flowers examined contained a spider, 64.8%

showed evidence of spider occupancy (webbing and/or spider present). Thrips were also

present in large numbers at all five sites: 48.4% of flowers contained thrips actively

foraging for pollen (Table 5). Fungus gnats, while frequently encountered in the seeps,

were only observed within D. californica flowers three times.

15

Table 2. Observed visits to Darlingtonia californica flowers. Aside from the one visit recorded by a European honeybee (Apis mellifera), Andrena nigrihirta was the only bee observed to visit the flowers. Numbers in parentheses indicate the number of visits to different flowers observed during a given time period(s).

Visitor Site Date Time Period(s) Observed

Apis mellifera SM2 6/12/08 4:34-4:49 p.m. Andrena nigrihirta DF 6/13/08 12:07-12:22 p.m. A. nigrihirta (4) N17 6/13/08 1:58-2:13 p.m. A. nigrihirta (3) SM2 6/14/08 10:30-10:45 a.m., 10:48-11:03 a.m. A. nigrihirta (2) CL 6/14/08 2:24-2:39 p.m. A. nigrihirta (3) DF 6/15/08 11:20-11:35 a.m., 11:41-11:56 a.m. A. nigrihirta (5) SM2 6/19/08 12:32-12:47 p.m., 1:45-2:00 p.m. A. nigrihirta (2) SM1 6/19/08 4:24-4:39 p.m. A. nigrihirta (5) N17 6/20/08 11:18-11:33 a.m., 12:12-12:27 p.m., 12:28-12:43 p.m. A. nigrihirta DF 6/20/08 2:20-2:35 p.m. A. nigrihirta (2) SM2 6/21/08 3:34-3:49 p.m., 3:50-4:05 p.m. A. nigrihirta (5) DF 6/22/08 10:51-11:06 a.m., 11:57-12:12 p.m., 12:13-12:28 p.m. A. nigrihirta (2) N17 6/22/08 1:17-1:32 p.m., 1:49-2:04 p.m. A. nigrihirta N17 7/2/08 11:33-11:48 a.m. A. nigrihirta SM1 7/3/08 11:55-12:10 p.m.

16

Table 3. Floral visitation rates. The mean number of visits a flower was expected to receive per hour and over its lifetime is presented for each study site. Standard error values for mean visits/hour are given in parentheses for each study site.

Site Visits/Hour Visits/Lifetime CL 0.016 (0.029) 1.60 SM1 0.041 (0.042) 2.71 SM2 0.073 (0.025) 4.84 N17 0.077 (0.025) 5.08 DF 0.067 (0.025) 4.42

17

Table 4. Duration of visits to Darlingtonia californica flowers by Andrena nigrihirta. Average visit duration was 2 minutes 8 seconds (SE=12 seconds

Site Date Time Period Observed Duration of Visit

CL 6/14/08 2:24-2:39 p.m. 1 min. 54 sec. DF 6/15/08 11:41-11:56 a.m. 2 min. 40 sec. SM2 6/19/08 12:32-12:47 p.m. 1 min. 15 sec. SM2 6/19/08 1:45-2:00 p.m. 2 min. 20 sec. SM1 6/19/08 4:24-4:39 p.m. 3 min. 4 sec. N17 6/20/08 11:18-11:33 a.m. 2 min. 15 sec. N17 6/20/08 12:12-12:27 p.m. 1 min. 49 sec. DF 6/20/08 2:20-2:35 p.m. 2 min. 33 sec. SM2 6/21/08 3:34-3:49 p.m. 1 min. 25 sec. DF 6/22/08 10:51-11:06 a.m. 3 min. 40 sec. DF 6/22/08 10:51-11:06 a.m. 2 min. 15 sec. DF 6/22/08 11:57-12:12 p.m. 2 min. 24 sec. N17 6/22/08 1:17-1:32 p.m. 1 min. 30 sec. N17 6/22/08 1:49-2:04 p.m. 50 sec.

18

Floral Mechanism/ Pollinator Behavior

Detailed observations of visits by A. nigrihirta revealed that the ovary shape of D.

californica promotes stigma contact by bees both as they enter and exit a flower (Figure

2). Immediately above the windows (towards the morphological base of the pendant

flower), the petals overlap and the underlying petal is appressed to the flared portion of

the ovary, which limits the ability of a pollinator the size of A. nigrihirta to enter a

window and crawl directly up onto the ovary on its way to collect pollen (Figure 3). In

between the windows, however, the petals bulge outward (Figure 3), and it is this space

that A. nigrihirta utilized to ascend the ovary to reach the stamens. This convex portion

of each of the five petals is located directly opposite each of the five windows, such that a

pollinator enters a window and walks in a straight line across the stigmas and then onto

the ovary (directed by the convex portion of the petal). The shape of D. californica’s

ovary has previously been thought to guide an insect pollinator away from the receptive

stigmatic surfaces as it exits the flower, thus preventing self-pollination. However, in

exiting the flower, the pollinator was observed to leave in the same fashion as it entered

(guided by petal convexities across the stigmas and out one of the windows, thus likely

effecting autogamy). This behavior was exhibited by multiple individuals, and was

consistent at all sites.

19

a b c d e f g h i j k l m n o p

20

Figure 2. Step by step foraging behavior of A. nigrihirta on a D. californica flower. The bee initially lands on the petals below the windows (a-c) and then enters a window and walks across stigmatic surfaces (d,e). The bee then utilizes the convex portion of one of the five petals to walk onto the ovary and up to collect pollen (f-i). Following pollen collection, the bee uses a petal convexity as before to walk down the ovary, across the stigmas again, and then out one of the windows (j-n). The flower is shown in d-m with one petal removed and half of the two lateral petals removed. F and k show the bee using the convex portion of the petal, which allows the bee to access the stamens.

21

Figure 3. Interior view of a D. californica flower with the lower portion of petals removed. Arrows highlight the distance between the petals and the ovary both immediately above a window (shorter arrow) and in between two adjacent windows (larger arrow). More space is provided for A. nigrihirta in between the windows than above them, which encourages the bee to enter a window and then walk across the stigmatic surfaces. The bee then utilizes the convex portion of the petal opposite the window it entered en route to the flower’s stamens.

22

Table 5. The percentage of examined flowers at each study site that contained one or more of the following: thrips, spiders, and spider webs (either inside or outside the flower). A total of 1125 flowers were individually examined (150 at CL, 225 at SM1, 250 at SM2, 250 at N17, and 250 at DF). “Evidence of Spider” column represents the percentage of examined flowers at each site that had a spider and/or webbing present. Only 3/1125 (0.27%) flowers contained one or more fungus gnats.

Site Web Outside Flw. Web Inside Flw. Spider Present Evidence of Spider Thrips

CL 38.7 13.3 16.7 48.7 25.3 SM1 48.9 39.6 20 61.8 40.9 SM2 47.2 30.4 24.8 57.2 31.6 N17 69.6 20 34 74 75.6 DF 68.8 30.8 31.2 75.6 58.4 TOTAL 56.2 27.7 26.2 64.8 48.4

23

Pollination Treatments

Both fruit and seed production varied depending on treatment. Fruit set was

significantly affected by floral treatment (χ2=37.69, p<<0.01) and treatment effects were

similar across all sites (χ2=0.85, p=0.99). Differences in mean seed production between

the three treatment groups were also evident at all five sites (SM1: F2, 63=65.35, p<<0.01;

SM2: F2, 65=53.76, p<<0.01; CL: F2, 59=52.49, p<<0.01; N17: F2, 58=46.31, p<<0.01; DF:

F2, 57=24.19, p<<0.01; Fig. 3).

Fruit set of D. californica populations near Scott Mountain and Mt. Eddy, CA was

high. Fruit production by unmanipulated flowers (76%) was marginally comparable to

that of hand-pollinated flowers (96%) (χ2=3.50, p=0.0615). Though fruit set by

unmanipulated flowers did not indicate significant pollen-limitation, seed production did.

Hand-pollinated flowers produced significantly more seeds than unmanipulated flowers

at each of the five study sites (Fig. 3), indicating that plants in all five populations

experienced pollen-limitation. On average, unmanipulated flowers produced 674

(n=114) seeds per capsule, versus 1422 (n=144) by hand-pollinated flowers and 439

(n=59) by emasculated flowers.

Self- and cross-pollination both contribute to D. californica reproductive success.

Emasculated flowers produced fruit and seed at all five sites, indicating that cross-

pollination occurred. However, overall fruit set of emasculated flowers (39%) was

significantly lower than that of unmanipulated flowers (76%) (χ2=17.79, p<0.001),

highlighting the importance of autogamous pollen transfer for fruit production.

24

Unmanipulated flowers produced significantly more seeds, on average, than emasculated

flowers at SM1 and SM2, but there was no significant difference found between these

two treatment groups at the remaining three sites (Fig. 3). Average seed production by

unmanipulated flowers was always higher than that of emasculated flowers, regardless of

statistical significance, suggesting that cross-pollination cannot account for all of the

seeds that were produced by unmanipulated flowers. Therefore, fruit and seed production

of naturally pollinated flowers were the result of both autogamous and xenogamous

pollen transfer.

Plant/ Insect Community Context

Plant communities in and around D. californica seeps were diverse. A total of 51

angiosperm species, all with blooming periods that at least partially overlapped that of D.

californica, were found at the study sites (Appendix 1). The plant communities at all five

sites were similar, with approximately 1/3 of all observed taxa found at every site. 42

concurrently blooming species were found at SM1 and SM2 combined, 35 at DF, 32 at

N17, and 27 at CL.

Species richness and percent ground cover were greater in the mesic areas within

the seeps compared to adjacent xeric habitats (Table 6, Appendix 2). In the seeps, D.

californica covered 31.7% of the ground and concurrently blooming plants covered

34.1% of the ground. In the more xeric areas surrounding the seeps, an average of 14.5%

of the ground was occupied by coflowering species. As judged by cover values, more

floral resources were available within the seeps than outside them.

25

Eighty eight pollinators (including the eight A. nigrihirta individuals collected

after visits to D. californica flowers) were collected from the community, representing

four orders of insects (Coleoptera, Diptera, Hymenoptera, and Lepidoptera) (Table 8).

Hymenopterans were the most abundant insect floral visitors, representing 62% of all

collected insect pollinators (n=49). Mason bees (Osmia spp.) were the most frequently

collected pollinator (n=23), followed by andrenid bees (Andrena spp., n=17) and

bumblebees (Bombus spp., n=9). A. nigrihirta was not collected on any plant other than

D. californica, but one individual was collected in flight (i.e., not on a flower) that carried

D. californica pollen.

26

Table 6. The percentage of ground covered by Darlingtonia californica and co-flowering plant species. The total percentage of ground covered by angiosperms both within and outside (50m) the seeps are shown in the first two columns. The percentage of ground covered by Darlingtonia californica within the seeps is also presented.

Site % cover within % cover outside % D. californica cover within

SM1 49.4 35.9 17.8

SM2 78.2 8.8 38.3

CL 63.6 5.4 34.7

DF 66.6 7.2 42.4

N17 71.2 15.2 25.4

TOTAL 65.8 14.5 31.7

27

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

SM1 SM2 N17 CL DF

Frui

t set

(%)

Emasculated Unmanipulated Hand-Pollinated

0

300

600

900

1200

1500

1800

SM1 SM2 N17 CL DF

Ave

rage

# o

f see

ds p

er fr

uit

Emasculated Unmanipulated Hand-Pollinated

Figure 4. Fruit and seed production by three treatment groups (emasculated, unmanipulated, and hand-pollinated flowers) at each

study site. Top: Fruit set (%) of three treatment groups at each field site. Emasculated flowers produced significantly fewer fruits than unmanipulated flowers. No significant difference was found between fruit production of unmanipulated vs. hand-pollinated flowers (χ2=3.50, p=0.0615). Bottom: Average number of seeds produced per capsule from three treatment groups at each field site. Different letters above bars indicate group means are significantly different.

a

b

c

a

b

c

a

a

b

aa

b

a a

b

28

Table 7. Pollinators collected at or near study sites. Order and family is presented for all pollinators (and genus for Hymenopterans). Numbers in parentheses indicate the number of individual pollinators collected from each group

Diptera (18) Anthomyiidae (1) Asilidae (1) Bombyliidae (6) Callophoridae (1) Muscidae (1) Syrphidae (8) Colleoptera (5) Hymenoptera (58) Andrenidae Andrena nigrihirta (9) Other Andrena spp. (7) Apidae Apis (1) Bombus (9) Colletidae Hylaeus (1) Halictidae Agapostemon (2) Lasioglossum (4) Megachilidae Osmia (23) Vespidae (2) Lepidoptera (7)

29

DISCUSSION

Near the summits of Scott Mountain and Mount Eddy, CA, populations of

Darlingtonia californica are pollinated by the solitary bee Andrena nigrihirta, with

additional pollination likely provided by spiders and small insects. Direct observations of

floral visits and the results of pollination treatments suggest pollination by both bees and

spiders. The success of emasculated flowers indicated that cross-pollination occurred at

all sites, implicating bees as pollen vectors. However, considering that average fruit and

seed production was always higher in unmanipulated versus emasculated flowers, some

level of autogamy must have occurred at all sites as well. Based on observations of visits

by bees and spiders, both organisms have the potential to effect self-pollination. Because

both self-pollination and cross-pollination contributed to fruit and seed production, both

spiders and bees likely contributed to D. californica reproductive success.

Both fruit and seed production by emasculated flowers implicate bees as pollen

vectors. However, because bees contact stigmatic surfaces when they exit a flower, they

have the ability to effect self-pollination and likely contributed to autogamous pollen

transfer as well. In light of this, the great majority of pollination may be mediated

exclusively by A. nigrihirta. Spiders, which were highly abundant on flowers and have

already been shown to effect autogamy in D. californica (Nyoka 2000), likely further

contributed to fruit and seed production via self-pollination. Spiders were constantly

seen patrolling and building webs on flowers, and in several instances webs were

30

constructed within flowers linking anthers and stigmas and were completely dusted with

pollen, indicating spider facilitated pollen movement within flowers. Thrips, which also

tend to remain resident within single flowers, were also present in large numbers and

were observed within D. californica flowers at all sites. Though fungus gnats do not

appear to be major pollinators near Scott Mountain and Mt. Eddy, CA, Nyoka and

Ferguson (1999) collected fungus gnats in southwestern Oregon that carried the pollen of

D. californica. Repeated floral visits by small insects like thrips and fungus gnats have

been shown to contribute substantially to fruit set in other angiosperms (Mesler et al.

1980, Zamora 1999), and may contribute to seed set in D. californica as well.

The lifespan of D. californica flowers is much longer than most temperate zone

flowering plants, and near sea level D. californica populations may bloom for as long as

48 days (Debuhr 1973). Assuming an active pollinator community, extended flower

longevity will result in an increase in pollinator visits (Primack 1985, Ashman and

Schoen 1994, Rathke 2003). The estimated visitation rates from this study show that

visits to D. californica flowers by its main insect pollinator, A. nigrihirta, are relatively

few. Despite low visit rates, flowers are still likely to receive at least one visit by A.

nigrihirta due to the flowers’ prolonged lifespans. A long blooming period not only

promotes visits by effective cross pollinators like bees, but also allows for repeated visits

by less effective pollinators like spiders and thrips. The longevity of D. californica

flowers may be an adaptation to deal with an unpredictable pollinator community and

favors pollination by several groups of organisms.

31

Plant species with overlapping flowering periods may either facilitate each other’s

pollination (Gross et al. 2000, Bruno et al. 2003, Moeller 2004) or inhibit it through

competition for pollinator services (Vamosi et al. 2006). Darlingtonia californica plants

at all five sites showed evidence of pollen-limitation of seed production. Due to the

abundance of heterospecific taxa with overlapping flowering times and the scarcity of

large bodied pollinators found to carry the pollen of D. californica, it is likely that these

populations are experiencing a reduction in seed set due to competition for floral visitors.

Other than spiders and thrips, A. nigrihirta was the only pollinator seen to consistently

visit D. californica flowers, and was the only insect taxon collected found to carry the

pollen of D. californica.

How close is the relationship between D. californica and A. nigrihirta? Though

many species of Andrena are specialists (Larsson 2005, Diamond et al. 2006), only

utilizing the pollen from particular groups of angiosperms, many are also generalist

foragers using a wide range of pollen hosts (Nyoka 2000). Across its range, which spans

North America and greatly exceeds that of D. californica, A. nigrihirta is a generalist that

has been observed to visit flowers from a diverse array of plants, including members of

Portulacaceae (Motten et al. 1982), Fabaceae (Tepedino et al. 1995), and Ericaceae

(Barry Rice, personal communication), along with D. californica. Three individuals of A.

nigrihirta were collected that carried both D. californica and Asteraceae pollen,

indicating that A. nigrihirta is utilizing floral resources from multiple species of

flowering plants. As the general biology and life history of A. nigrihirta is still poorly

described, future studies are needed to identify what floral resources are used by A.

32

nigrihirta and how much these bees rely on resources provided by D. californica in the

Pacific Northwest. Though D. californica is not considered threatened or endangered by

state or federal government, the California Native Plant Society has placed it on their

watch list of species with limited distributions (Skinner and Pavlik 1994). Because D.

californica may rely on A. nigrihirta for reproductive success, both organisms should be

considered in management efforts aimed at conserving present D. californica

populations.

Pollinator communities have been known to fluctuate in composition and

abundance from year to year (Wolfe 1988, Price et al. 2005), and past researchers trying

to determine the pollinators of D. californica may have inadvertently chosen time periods

when bees were largely absent. Others have witnessed visitation of D. californica by A.

nigrihirta as well, but only on a single day over the course of nine years observing the

flowers (Barry Rice, personal communication). Whether there is synchronicity between

the emergence of A. nigrihirta and the flowering period of D. californica throughout its

range needs to be determined. For D. californica populations near sea level, A. nigrihirta

may only be active for a fraction of the time D. californica is in bloom. Also, there may

be geographic regions where D. californica populations exist, but those of A. nigrihirta

do not. Either of these possibilities could potentially hinder efforts to witness floral

visitation. Alternatively, the foraging behavior of A. nigrihirta on D. californica flowers

may have limited prior pollinator sightings. After entering a D. californica flower the

bee is out of sight until emerging up to four minutes later. Therefore, if the initial

33

approach of the bee is not witnessed, an observer may never realize a flower had been

entered.

The bell-shaped ovary of D. californica was previously thought to prevent self-

pollination from occurring by guiding an insect pollinator away from stigmatic surfaces

as it exits a flower. However, following observations of visits by A. nigrihirta, it was

determined that the shape of the ovary actually promotes stigma contact both when bees

enter and exit flowers. This system provides an excellent example of the importance of

identifying and observing pollinators in order to truly understand the functional

significance of a plant’s floral morphology.

Future Research

While the present study sought to estimate the relative contributions of spiders vs.

other pollinators to D. californica seed set, these contributions were not directly

quantified. To better understand the importance of spiders as pollinators, future studies

should develop spider exclusion treatments that would prevent spiders from colonizing

flowers. By comparing the seed set of open-pollinated flowers with those that exclude

the presence of spiders, the contribution of spiders to seed and fruit production would

become evident. Spider exclusions may prove to be difficult, however. Not only can

some spiders jump relatively great distances (e.g. salticid spiders), but smaller spiders can

also “fly” by releasing a silken strand into the wind, which may then carry them to a new

location (potentially a D. californica flower). Therefore, simply coating the scape with a

34

sticky substance to limit cursorial colonization of flowers may not provide an adequate

barrier to all spiders. Further development of this method is needed.

There are a number of interesting ecological questions that have yet to be

addressed regarding D. californica pollination. For instance, how do spiders occupying

D. californica flowers interact with bees? Does the presence of spiders within a flower

deter visitation by bees, or do bees frequently fall victim to lurking spiders, and what

bearing does this have on D. californica reproductive success? Over the course of floral

observations conducted in this study, A. nigrihirta was seen “buzzing” flowers, i.e.

approaching flowers but not entering them, more frequently than entering flowers (37

flowers visited, 50 flowers buzzed). This behavior could be the result of floral marking

by bees, which may be done to alert future visitors of resource availability (Schmitt and

Bertsch 1990, Goulson et al. 2001), but may also be the result of altered foraging

behavior due to the presence of flower-occupying spiders (Bruce et al. 2005, Goncalves-

Souza 2008). Also, do the same floral traits that promote pollen deposition on stigmatic

surfaces by bees (shape of ovary, etc.) also promote pollen deposition by spiders, or

should we expect divergence of floral morphology in D. californica populations that

occur in areas where A. nigrihirta is absent over time? As we seek to explain the

adaptive significance of D. californica’s floral traits, we need to understand, in greater

detail, the effects of these multi-species interactions on trait selection.

35

LITERATURE CITED

Ashman, T. L. and D. J. Schoen. 1994. How long do flowers live? Nature 371: 788-791.

Austin, R. M. 1875-1877. Letters to W. M. Canby on Darlingtonia. The Society of Natural History of Delaware, Wilmington, DE: Wilmington Institute Free Library.

Bruce, M. J., A. M. Heiling, and M. E. Herberstein. 2005. Spider signals: are web decorations visible to birds and bees? Biology Letters 1: 299-302.

Bruno, J. F., J. J. Stachowicz, and M. D. Bertness. 2003. Inclusion of facilitation into ecological theory. Trends in Ecology & Evolution 18: 119-125.

Crepet, W. L., and K. J. Niklas. 2009. Darwin’s second “abominable mystery”: why are there so many angiosperm species? American Journal of Botany 96: 366-381.

Debuhr, L. E. 1973. Distribution and reproductive biology of Darlingtonia californica. Master’s thesis. Claremont Graduate School, Claremont, CA.

Diamond, A. R., D. R. Folkerts, and R. S. Boyd. 2006. Pollination biology, seed dispersal, and recruitment in Rudbeckia auriculata (Perdue) Kral, a rare southeastern endemic. Castanea 71: 226-238.

Elder, C. L. 1994. Reproductive biology of the California pitcher plant (Darlingtonia californica). Fremontia 22: 29-30.

Elder, C. L. 1997. Reproductive biology of Darlingtonia californica. Master’s thesis. Humboldt State University, Arcata, CA.

Fenster, C. B., W. S. Armbruster, and P. Wilson. 2004. Pollination syndromes and floral specialization. Annual Review of Ecology, Evolution and Systematics 35: 375-403.

Forrest, J. and J. D. Thomson. 2009. Pollinator experience, neophobia and the evolution of flowering time. Proceedings of the Royal Society Biological Sciences Series B 276: 935-943.

Goncalves-Souza, T., P. M. Omena, J. C. Souza, and G. Q. Romero. 2008. Trait-mediated effects on flowers: artificial spiders deceive pollinators and decrease plant fitness. Ecology 89: 2407-2413.

36

Goulson, D. 1999. Foraging strategies of insects for gathering nectar and pollen, and implications for plant ecology and evolution. Perspectives in Plant Ecology Evolution and Systematics 2: 185-209.

Goulson, D., J. W. Chapman, W. O. H. Hughes. 2001. Discrimination of unrewarding flowers by bees; direct detection of rewards and use of repellent scent marks. Journal of Insect Behavior 14: 669-678.

Gross, C. L., D. A. Mackay, and M. A. Whalen. 2000. Aggregated flowering phenologies among three sympatric legumes: the degree of non-randomness and the effect of overlap on fruit set. Plant Ecology 148: 13-21.

Hintze, J. 2004. NCSS and PASS. Number Cruncher Statistical Systems. Kaysville, Utah.

Hu, S., D. L. Dilcher, D. M. Jarzen, and D. W. Taylor. 2008. Early steps of angiosperm-pollinator coevolution. Proceedings of the National Academy of Sciences of the United States of America 105: 240-245.

Juniper, B. E., R .J. Robbins and D. M. Joel. 1989. The carnivorous plants. Academic Press, London. 353 pp.

Kearns, C. A. and D. W. Inouye. 1993. Techniques for pollination biologists. University Press of Colorado, Niwot. 583 pp.

Larsson, M. 2005. Higher pollinator effectiveness by specialist than generalist flower-visitors of unspecialized Knautia arvensis (Dipsacaceae). Oecologia 146: 394-403.

Macfarlane, J. M. 1908. Sarraceniaceae. In A. Engler [ed.], Das Pflanzenreich. Regni vegetabilis conspectus, vol. IV, pp. 1–39. Verlag von WilhelmEngelmann, Leipzig, Germany.

Mesler, M. R., J. D. Ackerman and K. L. Lu. 1980. The effectiveness of fungus gnats as pollinators. American Journal of Botany 67: 564-567.

Moeller, D. A. 2004. Facilitative interactions among plants via shared pollinators. Ecology 85: 3289‐3301.

Motten, A. F., D. R. Campbell, D. E. Alexander, and H. L. Miller. 1981. Pollination effectiveness of specialist and generalist visitors to a North Carolina population of Claytonia virginica. Ecology 62: 1278-1287.

37

Ne’eman, C., G. Ne’eman and A. M. Ellison. 2006. Limits to reproductive success of Sarracenia purpurea (Sarraceniaceae). American Journal of Botany 93: 1660-1666.

Nyoka, S. E., and C. Ferguson. 1999. Pollinators of Darlingtonia californica Torr., the California pitcher plant. Natural Areas Journal 19: 386-391.

Nyoka, S.E. 2000. The spider and the fly: a proposed pollination scenario for Darlingtonia californica, the California pitcher plant. Field research grant report for the Native Plant Society of Oregon.

Pauw, A., J. Stofberg, R. J. Waterman. 2008. Flies and flowers in Darwin’s race. Evolution 63: 268-279.

Price, M.V., N. M. Waser, R. E. Irwin, D. R. Campbell, and A. K. Brody. 2005. Temporal and spatial variation in pollination of a montane herb: a seven-year study. Ecology 86: 2106-2116.

Primack, R. B. 1985. The longevity of individual flowers. Annual Review of Ecology and Sytematics 16: 15-37.

Rathcke, B. J. 2003. Floral longevity and reproductive assurance: seasonal patterns and an experimental test with Kalmia latifolia (Ericaceae). American Journal of Botany 90: 1328-1332.

Renner, S. S. 1989. Floral biological observations on Heliamphora tatei (Sarraceniaceae) and other plants from Cerro de la Neblina in Venezuela. Plant Systematics and Evolution 163: 21-29.

Schmitt, U., and A. Bertsch. 1990. Do foraging bumblebees scent-mark food sources and does it matter? Oecologia 82: 137-144.

Schnell, D. E. 1976. Carnivorous plants of the U. S. and Canada. John F. Blair, Winston- Salem. 125 pp.

Skinner, M. W. and B. M. Pavlik. 1994. California Native Plant Society’s inventory of rare and endangered vascular plants of California. Special publication No. 1. Fifth Edition. California Native Plant Society, Sacramento, CA. 338 pp.

Tepedino, V. J., T. L. Griswold, and W. R. Bowlin. 1995. Pollinator sharing by three sympatric milkvetches including the endangered species Astragalus montii. Great Basin Naturalist 55: 19-25.

38

Thomas, K. and D. M. Cameron. 1986. Pollination and fertilization in the pitcher plant Sarracenia purpurea. American Journal of Botany 73: 678.

Valdivia, C. E., and H. M. Niemeyer. 2006. Do floral syndromes predict specialization in plant pollination systems? Assessment of diurnal and nocturnal pollination of Escallonia myrtoidea. New Zealand Journal of Botany 44: 135-141.

Vamosi, J. C., T. M. Knight, J. A. Steets, S. J. Mazer, M. Burd, and T. L. Ashman. 2006. Pollination decays in biodiversity hotspots. Proceedings of the National Academy of Sciences of the United States of America 103: 956-961.

Vogel, S. 2006. Floral syndromes: empiricism versus typology. Botanische Jahrbuecher fuer Systematik Pflanzengeschichte und Pflanzengeographie 127: 5-11.

Vogelei, A., and R. Greissl. 1989. Survival strategies of the crab spider Thomisus onustus Walckenaer 1806 (Chelicerata, Arachnida, Thomisidae). Oecologia 80: 513-515.

Whittaker, R. H. 1954. The ecology of serpentine soils IV. The vegetational response to serpentine soils. Ecology 35: 275-288.

Wolfe, L. M., S. C. H. Barrett. 1988. Temporal changes in the pollinator fauna of tristylous Pontederia cordata, an aquatic plant. Canadian Journal of Zoology 66: 1421-1424.

Zamora, R. 1999. Conditional outcomes of interactions: the pollinator-prey conflict of an insectivorous plant. Ecology 80: 786-795.

Zhang, L., S. C. H. Barrett, J. Y. Gao, J. Chen, W. W. Cole, Y. Liu, Z. L. Bai, and Q. J. Li. 2005. Predicting mating patterns from pollination syndromes: the case of ‘sapromyophily’ in Tacca chantrieri (Taccaceae). American Journal of Botany 92: 517-524.

39

Appendix A. Plant species in coincident bloom with Darlingtonia californica near Scott Mountain and Mt. Eddy, CA.

Species Name Family Habitat Flw. First Obs. Fruit First Obs. Sites Found

Lomatium sp. Apiaceae xeric

6/22/2008

7/12/2008

CL, SM1, SM2

Achillea millefolium Asteraceae

mesic

6/19/2008

7/12/2008

SM1, SM2, CL, DF, N17

Aster alpigenus

Asteraceae

mesic 6/20/2008 7/1/2008

SM1,SM2, N17,DF

Eriophyllum lanatum

Asteraceae

xeric

6/22/2008

7/12/2008

N17, DF

Helenium bigelovii

Asteraceae

mesic

6/22/2008

7/12/2008

SM1, SM2, CL

Senecio integerrimus var.exaltatus

Asteraceae

xeric

6/6/2008

7/1/2008

SM1,SM2, CL, N17,DF

Senecio triangularis

Asteraceae

xeric

6/19/2008

7/1/2008

SM1,SM2, CL, N17,DF

Taraxacum officinale

Asteraceae

mesic

6/6/2008

7/1/2008

SM1,SM2, CL, N17, DF

Arenaria congesta

Caryophyllaceae

xeric

6/22/2008

7/12/2008 N17

Pseudostellaria jamesiana

Caryophyllaceae

xeric

6/22/2008

7/12/2008

SM1, SM2, DF, N17

Silene lemmonii

Caryophyllaceae

xeric

6/22/2008

7/12/2008

SM1, SM2, CL N17, DF

Eriophorum criniger

Cyperaceae

mesic

6/21/2008

7/11/2008


Arctostaphylos sp.

Ericaceae

xeric

6/6/2008

7/1/2008

SM1, SM2, CL

Rhododendron occidentale

Ericaceae

xeric

6/6/2008

7/12/2008 SM1, SM2

Lupinus croceus

Fabaceae

xeric

6/22/2008

7/12/2008 N17,DF

Lotus pinnatus

Fabaceae

mesic

6/22/2008

7/12/2008

SM1,SM2, CL, N17,DF

40

Appendix A. Plant species in coincident bloom with Darlingtonia californica near Scott

Mountain and Mt. Eddy, CA. Species Name Family Habitat Flw. First Obs. Fruit First Obs. Sites Found Trifolium longipes

Fabaceae

mesic

6/19/2008

7/1/2008

SM1,SM2, CL, N17,DF

Ribes roezlii

Grossulariaceae

xeric

6/19/2008

7/1/2008

SM1,SM2, N17

Sisyrinchium idahoense ssp.occidentale

Iridaceae

mesic

6/6/2008

7/4/1998


Prunella vulgaris var. lanceolata

Lamiaceae

mesic

6/22/2008

7/12/2008

SM1, SM2, DF

Allium validum Liliaceae mesic 6/22/2008 7/12/2008 N17 Calochortus nudus

Liliaceae

xeric

6/19/2008

7/11/2008

SM1,SM2,CL, N17, DF

Calochortus tolmiei

Liliaceae

xeric

6/19/2008

7/11/2008

SM1, SM2, CL, N17, DF

Dichelostemma multiflorum

Liliaceae

xeric

6/22/2008

7/12/2008 SM1, SM2

Hastingsia alba

Liliaceae

mesic

6/22/2008

7/12/2008

SM1,SM2,CL,N17, DF

Lilium pardalinum ssp. shastense

Liliaceae

xeric

6/22/2008


Narthecium californicum Liliaceae

mesic

6/22/2008

7/12/2008 SM1, SM2

Xeropyhylum tenax

Liliaceae

xeric

6/19/2008

7/1/2008 SM1, SM2

Sidalcea glaucescens Malvaceae

xeric

6/22/2008

7/12/2008

SM1, SM2, N17

Sidalcea oregana

Malvaceae

mesic

6/22/2008

7/12/2008

SM1, SM2, N17, DF

Epilobium ciliatum ssp. ciliatum Onagraceae

mesic

6/22/2008

7/12/2008

SM1, SM2, DF

Corallorhiza maculata Orchidaceae

xeric

6/22/2008

SM1, SM2

41


Mountain and Mt. Eddy, CA. Species Name Family Habitat Flw. First Obs. Fruit First Obs. Sites Found Platanthera leucostachys Orchidaceae

mesic

6/19/2008

SM1, SM2, N17, DF

Platanthera sparsiflora Orchidaceae

mesic

6/22/2008

DF

Polygonium bistortoides Polygonaceae

mesic

6/22/2008

7/11/2008

SM1, SM2, N17, DF

Dodecatheon jeffreyi Primulaceae

mesic

6/6/2008

7/12/2008

N17,SM1,SM2,CL, DF

Aquilegia formosa Ranunculaceae

xeric

6/19/2008

7/12/2008


Caltha leptosepala var. biflora Ranunculaceae

mesic

6/6/2008

7/12/2008 CL , N17, DF

Delphinium glaucum Ranunculaceae

xeric

6/21/2008

7/12/2008

SM1, SM2, CL, N17, DF

Amelanchier utahensis Rosaceae

xeric

6/6/2008 7/12/2008 SM1,SM2

Potentilla drummondii ssp. breweri Rosaceae mesic

6/20/2008

7/4/2008


Rosa woodsii var. ultramontana Rosaceae

xeric

6/22/2008

7/12/2008 SM1, SM2

Spiraea densiflora Rosaceae

mesic

6/22/2008

7/12/2008 SM1,SM2

Castilleja sp. Scrophulariaceae xeric 6/19/2008 7/12/2008 SM1,SM2 Mimulus guttatus Scrophulariaceae

mesic

6/22/2008

7/12/2008


Mimulus primuloides Scrophulariaceae

mesic

6/6/2008

7/4/2008


Penstemon speciosus Scrophulariaceae

xeric

6/22/2008

7/12/2008 SM1, SM2

Viola glabella Violaceae mesic 6/22/2008 7/11/2008 DF

42


Mountain and Mt. Eddy, CA. Species Name Family Habitat Flw. First Obs. Fruit First Obs. Sites Found Viola lobata ssp. lobata Violaceae

mesic

6/6/2008

7/4/2008

SM1,SM2, CL, N17,DF

Viola sororia ssp. affinis Violaceae

mesic

6/6/2008

7/4/2008

SM1,SM2

Viola maclosky Violaceae mesic 6/6/2008 7/4/2008 SM1, SM2

43

Appendix B. Results of percent ground cover analyses. Separate tables are presented for ground cover within versus outside seeps at all five study sites.

SM1 (within seep) Plot Aster

alpigenus Darlingtonia californica

Hastingsia Alba

Helenium bigelovii

Lotus pinnatus

Narthecium californicum

Potentilla drummondii

Sisyrinchium sp.

Trifolium longipes

1 0 14 8 0 15 0 0 4 0 2 4 11 0 0 17 3 0 7 0 3 0 29 3 6 2 0 0 16 3 4 2 16 1 4 9 2 0 12 4 5 4 17 4 4 10 2 0 11 7 6 2 11 1 3 2 0 0 10 0 7 1 11 4 3 4 0 0 6 0 8 0 10 3 1 6 1 0 8 4 9 2 9 2 3 9 3 0 9 3 10 2 9 7 5 4 0 0 12 7 11 3 6 0 0 5 2 0 9 0 12 1 14 10 4 8 0 1 6 9 13 0 9 0 5 13 0 0 13 12 14 0 21 0 4 19 0 0 20 0 15 2 17 0 1 15 3 0 7 0 16 5 13 1 2 3 6 0 13 2 17 3 27 0 7 1 0 0 10 1 18 2 16 0 8 8 0 0 26 4 19 3 26 2 10 9 2 0 11 0 20 0 9 6 16 8 0 0 14 6 21 1 16 5 14 14 0 0 5 1 22 2 33 2 6 9 0 0 12 0 23 0 37 1 1 4 0 0 13 0 24 4 34 0 5 5 0 0 8 6 25 1 29 3 2 6 3 0 4 3 Average: 1.76 17.76 2.52 4.56 8.2 1.08 0.04 10.64 2.88

44


SM1 (outside seep) Plot Achillea millefolium Arctostaphylos sp. Ceanothus sp. Rosa woodsii Senecio integerrimus 1 0 0 7 7 2 2 0 0 0 0 2 3 0 0 43 0 1 4 0 0 5 0 0 5 0 85 0 0 0 6 0 89 0 0 0 7 0 65 0 0 1 8 0 0 0 0 2 9 0 22 2 0 2 10 0 0 8 27 2 11 3 0 0 40 3 12 0 94 0 0 1 13 1 9 0 45 0 14 0 84 0 0 4 15 0 18 0 0 0 16 0 0 0 0 2 17 0 0 0 0 2 18 0 0 27 76 2 19 0 0 11 21 1 20 0 0 0 0 31 21 0 0 26 0 1 22 0 0 0 0 2 23 0 0 13 8 1 24 0 0 0 0 0 25 0 0 0 0 0 Average: 0.16 18.64 5.68 8.96 2.48

45


SM2 (within seep) Plot Aster alpigenus Darlingtonia

californica Dodecatheon jeffreyi

Hastingsia alba Helenium bigelovii

Lotus pinnatus Mimulus primuloides

Sisyrinchium sp.

Trifolium longipes

1 0 14 0 0 8 0 0 6 0 2 0 32 3 0 2 0 0 18 0 3 2 27 0 2 10 0 0 5 0 4 6 72 0 6 1 0 0 11 5 5 0 94 8 0 0 0 0 0 3 6 12 43 0 0 0 0 8 0 0 7 11 25 0 0 0 0 14 4 0 8 14 37 0 3 0 0 0 4 0 9 12 62 3 2 0 0 0 3 0 10 27 73 0 0 0 0 0 4 0 11 15 62 0 6 8 0 0 3 0 12 19 54 4 0 4 0 0 8 17 13 22 23 7 4 0 0 0 3 0 14 11 19 3 12 0 0 0 10 5 15 0 13 0 12 0 0 59 0 0 16 12 9 6 23 0 0 46 3 0 17 4 63 0 18 3 0 0 16 15 18 15 39 2 2 2 0 0 14 0 19 21 40 0 12 0 0 0 32 2 20 3 13 9 2 29 8 0 9 0 21 21 21 7 3 20 0 0 26 0 22 11 24 9 0 0 0 0 8 0 23 31 46 8 3 0 0 0 6 0 24 13 31 11 2 2 0 0 16 0 25 2 22 2 5 24 0 0 5 4 Average: 11.36 38.32 3.28 4.68 4.52 0.32 5.08 8.56 2.04

46

Appendix B. Results of percent ground cover analyses. Separate tables are presented for ground cover within versus outside

seeps at all five study sites. SM2 (outside seep) Plot Arctostaphlyos sp. Castilleja sp. Rosa woodsii Silene lemmonii 1 0 0 34 0 2 0 0 27 0 3 0 0 0 0 4 0 0 0 0 5 0 0 0 0 6 0 0 0 0 7 0 0 11 0 8 0 0 0 0 9 0 0 4 0 10 0 0 1 0 11 0 0 5 2 12 0 0 0 0 13 0 0 5 0 14 0 0 0 0 15 0 0 18 0 16 0 0 0 0 17 0 0 2 0 18 0 0 0 4 19 0 0 31 1 20 0 0 3 0 21 33 0 0 0 22 16 3 0 0 23 0 0 0 3 24 0 0 3 4 25 0 0 0 11 Average: 1.96 0.12 5.76 1

47


seeps at all five study sites. CL (within seep) Plot Darlingtonia

californica Hastingsia alba Helenium bigelovii Lotus pinnatus Mimulus primuloides Sisyrinchium sp.

1 16 7 0 5 0 0 2 29 13 0 0 0 0 3 26 3 5 7 0 0 4 27 0 5 0 0 0 5 9 0 8 0 0 0 6 19 0 8 0 0 9 7 37 0 2 2 0 5 8 29 3 8 4 0 7 9 7 6 8 4 0 19 10 6 7 1 0 7 0 11 41 12 5 0 0 1 12 21 6 12 0 0 4 13 11 15 7 0 0 10 14 37 29 5 0 0 4 15 48 19 4 0 0 11 16 88 6 4 0 0 12 17 83 9 8 0 0 4 18 49 12 7 4 0 6 19 43 23 3 0 0 18 20 83 17 4 0 0 9 21 31 3 16 36 0 19 22 21 4 7 32 0 6 23 62 6 7 21 0 4 24 11 5 14 19 0 18 25 33 4 12 21 23 3 Average: 34.68 8.36 6.4 6.2 1.2 6.76

48


seeps at all five study sites. CL (outside seep) Plot Achillea millefolium Amelanchier utahensis Arenaria congesta Lomatium sp. Pseudostellaria

jamesiana Trifolium longipes

1 9 5 8 0 7 0 2 0 0 0 0 0 0 3 0 0 0 0 0 0 4 0 0 0 0 0 0 5 0 0 0 0 0 0 6 0 5 0 7 0 0 7 0 0 2 2 10 2 8 0 0 0 0 3 0 9 0 0 0 3 0 1 10 0 0 0 0 0 1 11 0 0 0 0 0 0 12 0 0 0 0 0 0 13 0 0 2 0 0 4 14 0 0 2 4 0 1 15 0 0 0 0 0 1 16 0 0 1 4 0 1 17 0 0 5 0 0 6 18 0 0 0 0 0 0 19 0 0 0 3 0 2 20 0 0 2 2 0 0 21 0 0 0 0 0 2 22 3 0 0 3 0 6 23 0 0 0 11 0 1 24 0 0 0 2 0 0 25 0 0 0 0 0 0 Average: 0.48 0.4 0.88 1.64 0.8 1.12

49


seeps at all five study sites. N17 (within seep) Plot Aster

alpigenus Caltha leptosepala

Darlingtonia californica

Dodecatheon jeffreyi

Epilobium ciliatum

Hastingsia alba

Helenium bigelovii

Lotus pinnatus

Mimulus guttatus

Senecio triangularis

Sisyrinchium sp.

1 0 30 1 0 2 26 9 0 0 4 4 2 0 26 27 2 0 18 6 2 0 0 7 3 2 4 22 8 0 13 0 3 0 1 3 4 0 2 39 3 0 3 4 27 0 0 0 5 0 60 29 5 0 0 4 6 0 0 2 6 2 51 16 0 0 0 0 12 0 0 1 7 8 0 20 0 0 26 7 41 0 0 0 8 13 7 34 0 0 0 6 3 4 0 7 9 0 74 4 0 0 0 1 0 0 0 0 10 0 19 0 0 3 7 5 0 0 9 0 11 0 21 0 0 0 0 7 7 0 12 0 12 0 0 14 3 0 3 6 4 0 0 2 13 25 0 25 2 0 3 7 9 0 0 6 14 12 3 22 7 0 0 2 22 0 0 2 15 0 14 26 5 0 2 7 21 0 0 0 16 0 0 5 8 0 0 7 16 0 0 5 17 0 9 18 7 0 15 1 12 0 0 15 18 0 0 42 11 0 8 0 0 0 1 4 19 0 0 40 17 0 26 0 0 0 0 6 20 0 0 43 5 0 2 0 1 0 0 4 21 0 7 9 27 0 0 7 5 0 1 0 22 0 0 52 2 0 0 0 0 0 4 3 23 0 0 67 4 0 13 7 4 0 0 10 24 7 5 29 3 0 9 0 12 0 0 8 25 0 0 51 0 0 7 4 7 0 0 4 Average: 2.76 13.3 25.4 4.76 0.2 7.24 3.88 8.56 0.16 1.28 3.72

50


N17 (outside seep) Plot Achillea

millefolium Arenaria congesta

Eriophyllum lanatum

Lomatium sp. Pseudostellaria jamesiana

Senecio integerrimus

Taraxacum officinale

Viola sororia

1 7 3 0 0 0 3 0 3 2 5 0 0 1 0 0 2 2 3 0 0 3 0 4 0 1 2 4 0 0 0 3 0 0 0 1 5 0 0 0 0 6 0 0 5 6 6 0 0 0 0 1 0 0 7 5 0 9 0 3 2 0 0 8 7 0 3 0 4 0 0 1 9 8 14 5 0 0 0 0 3 10 3 0 0 0 0 2 0 0 11 20 7 0 0 0 4 1 0 12 2 0 0 0 5 5 0 1 13 0 0 2 0 3 2 1 0 14 2 0 4 0 4 0 0 0 15 1 0 5 0 2 0 0 0 16 0 0 0 0 4 0 0 0 17 0 0 7 3 0 7 0 2 18 6 2 13 2 0 2 0 0 19 4 0 0 0 4 0 1 0 20 6 0 2 0 1 0 0 0 21 3 1 10 0 2 5 0 0 22 6 0 11 0 0 7 0 0 23 3 11 0 0 6 2 0 2 24 5 0 0 0 6 0 0 0 25 0 0 3 0 1 0 0 0 Average: 3.96 1.52 3.08 0.36 2.2 1.68 0.24 0.88

51


DF (within seep) Plot Aster

alpigenus Darlingtonia californica

Hastingsia alba

Helenium bigelovii

Mimulus primuloides

Platanthera leucostachys

Sidalcea oregano

Sisyrinchium sp.

Trifolium longipes

Violoa sororia

1 2 35 25 0 0 0 0 0 0 0 2 4 14 18 2 0 0 0 10 0 0 3 9 70 6 8 0 2 0 0 0 0 4 0 61 11 5 0 0 0 0 16 0 5 0 50 16 0 0 0 0 2 0 0 6 4 62 11 9 0 0 0 0 7 0 7 0 43 13 11 0 0 0 0 5 4 8 7 20 14 0 0 0 0 0 2 0 9 2 23 10 3 0 0 0 0 0 0 10 3 37 5 2 0 5 0 0 0 0 11 3 11 3 0 0 0 0 2 9 0 12 3 26 12 6 0 0 0 4 3 0 13 1 43 8 0 0 0 0 3 7 0 14 5 25 9 15 0 0 0 2 3 0 15 0 26 13 11 0 0 0 0 0 0 16 3 34 37 0 0 0 0 3 0 0 17 5 43 4 0 0 0 0 0 0 0 18 5 31 7 7 0 0 0 9 0 0 19 6 46 9 10 19 0 0 0 0 0 20 2 62 2 0 0 0 0 3 0 0 21 9 38 8 0 0 0 5 0 0 0 22 3 71 6 8 0 0 5 0 0 0 23 5 41 0 9 0 0 0 3 0 0 24 0 81 4 0 0 0 0 2 0 0 25 4 67 2 16 0 0 8 0 0 0 Average: 3.4 42.4 10.12 4.88 0.76 0.28 0.72 1.72 2.08 0.16

52


DF (outside seep) Plot Arctostaphylos sp. Delphinium glaucum Lupinus croceus Pseudostellaria

jamesiana Ribes roezlii Senecio integerrimus

1 0 0 71 0 0 0 2 0 0 0 0 0 0 3 0 0 0 0 0 0 4 0 0 0 0 0 0 5 0 0 0 2 47 0 6 0 0 0 0 0 0 7 0 0 0 0 0 0 8 0 0 0 0 0 0 9 0 0 0 0 0 2 10 0 0 0 0 0 3 11 0 0 0 4 0 0 12 0 0 0 0 0 0 13 0 0 6 3 0 0 14 0 0 0 0 0 0 15 0 0 0 2 0 0 16 0 0 0 5 0 0 17 0 0 0 0 0 0 18 0 13 0 0 0 0 19 0 0 0 0 0 0 20 0 0 0 0 0 0 21 13 0 0 3 0 0 22 0 0 0 0 0 0 23 0 0 0 0 0 0 24 0 0 2 0 0 0 25 0 0 0 0 0 0 Average: 0.52 0.52 3.16 0.76 1.88 0.2

53

Documents

POLLINATION BIOLOGY OF DARLINGTONIA CALIFORNICA, THE