Invasive Species as a global threat to biodiversity

What prevents species from dispersing globally?

Geographic Barriers:

Oceans

Mountains

Deserts

Large Lakes

Barriers are in the eye of the beholder: what is a barrier for one species is not a barrier to another

e.g. mountains may restrict plant distributions, but not birds

Limits to Dispersal

• Wallace identified 6 global biodiversity realms, each different from the other.

Nearctic, Ethiopian Palearctic, Oriental Australasian•Neotropical,

Invasive Species: Species introduced to regions outside of their historic native range;

Species are being transported across these barriers at an increasing rate owing to human movement and commerce (50,000 times greater rate of spread than by natural dispersal in some cases) major vectors are planes, ships and humans

Invasive Species:

• What are they?

• Why should we care?

• ecological concerns

• human, plant and animal health

• economic concerns

What are invasive Species?

• Invasive Species– implies exotic and a threat to native species

• Exotic Species– from another part of the world

• Introduced Species– implies introduction but not a threat

• Alien Species– Implies introduction to a particular ecosystem

Classical Model of Invasion

Natural Colonization

Establishment requires dispersal across barriers, colonization in acceptable number, and successful reproduction

Natural colonization and human-mediated invasion

from Rahel (2002), Homogenization of freshwater faunas. Ann. Rev. Ecol. System.

• Only some novel species will survive and establish self-sustaining populations in the novel habitat.

• A subset of these species may not only survive, but become invasive, dominating the new community and even causing the extinction of natives.

• But, what allows a species to become invasive?

What allows invaders to invade?

What allows invaders to invade?

Broad Environmental Tolerance

- posses life history traits that confer superior colonizing ability or ability to acclimate to a wide range of habitats.

Local Adaptation

- readily adapt to local selective pressures.

Sexton et al. 2002. Ecological Applications 12: 1652-1660.

Evolution of Increased Competitive Ability Hypothesis (EICA)

• As applied to plants –

• Under identical growing conditions, species will produce more biomass in an area where it has been introduced vs. in its native range.

• Invasive species will exhibit lower herbivore defense rates in introduced range than in native range.

• A species is not as fit (in its native habitat) at the time of introduction vs. when it becomes invasive.

Blossey and Notzold. 1995. Journal of Ecology 83(5):887-889.

Chinese Tallow Tree (Sapium sebiferum)

• Introduced to SE US in 1700s from China

• Soap from seed oils ornamental

• Naturalized throughout much of South

• Alters access to light for other plants

• Leaves contain toxins that can kill other plants

• Creates monospecific stands

• Collected seeds from native and introduced ranges

• Seeds planted and raised for ~ 1 year in native range

• Measured growth and herbivore leaf damage

• Compared native plants with individuals from introduced range

Chinese Tallow Tree: A Test of EICA hypothesis

Zou et al. 2006. Oecologia 150:272-281.

• Shoot mass, root mass and total mass higher in invasive range

• Leaves tended to be more damaged by herbivores when grown in native range

Chinese Tallow Tree (Sapium sebiferum)

Sapium has evolved reductions in defense allocation and increased growth and reproduction in the absence of

herbivores in its introduced range.

Growth

Leaf Damage

Do invasives evolve?Experimental design

18th centuryearly 20th century

• Collected seeds from source trees in China(native range), Georgia, Texas and Louisiana.

• grown in field for 14 years and then measured size, seed production, leaf chemistry and defense chemicals.

Siemann & Rogers. 2001. Ecology Letters 4:514-518.

Tallow Tree EICA Results

• Native genotypes were less vigorous than invasive genotypes. Propagules from areas of recent invasion produced largest genotypes.

• Foliage from native genotypes was of ~ higher quality and had greater concentrations of defense compounds.

Siemann & Rogers. 2001. Ecology Letters 4:514-518.

20th century

17th century

native

Invasion model

Local adaptation

Phenotypic plasticity

Introduced Naturalized Lag Invasive

Sexton et al. 2002. Ecological Applications 12:1652-1660.

• Plasticity and adaptive evolution can lead to greater invasiveness

Why should we care?

Lawler et al. (2006), Frontiers in Ecology & the Environment

Causes of Global Species Endangerment

All Species

Marine Species

0.0

0.5

1.0 Arctic

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1.0 Boreal

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0.5

1.0 Temperate Forests

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0.5

1.0 Grassland

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0.5

1.0 Lakes

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1.0 Streams

Climat

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CO 2

Land

use

Driversof

SpeciesChange

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CO 2

Land

use

Invasive Species a major threat to some systems (Sala et al. Science 2000)

Impacts of Invasive Species and Changes in Biodiversity

Chapin et al. 2000. Nature 405: 234-242.

Negative Impacts of Invasive Species

Ecosystem Level Impacts

• Disturbance Regimes• Hydrology: Alterations of Water Regimes• Geomorphological processes (erosion, sedimentation)• Soil chemistry

Community or Population Level Impacts

• Habitat structure• Community composition• Resource competition• Population reductions, eliminations• Genetic Impacts

Alteration of disturbance regimes

1) cogon grass (Imperata cylindrica): increases vulnerability of vegetation to fire, which it itself is invulnerable to since it regenerates quickly from belowground rhizomes (roots); result is that the plant completely takes over the region.

Alteration of disturbance regimes

Hydrology: alteration of water regimes

salt cedar (Tamarisk): absorbs large quantities of water along riverbanks in arid regions, and excretes salt into soils; forms monocultures.

Gaskin and Shaal. 2002. PNAS 99(17): 11256-11259.

Soil chemistry

Zou et al. 2006. Oecologia 150: 272-281.

Community or Population Level Impacts

Community Composition and Structure

a) Predation

b) Competition

c) Parasitism

d) Disease

Homogenization of Flora and Fauna

Introduced species

X extirpated species

Rahel (2002), Homogenization of freshwater faunas. Ann. Rev. Ecol. System.

Homogenization of Flora and Fauna

E. Taylor, Canadian Journal of Fisheries and Aquatic Sciences (2004)

• more species change due to introduction of nonindigenous fishes than to loss of native fishes

• this pattern may not be general - may vary from system to system

Predation

Lake Victoria, Africa

• introduced Nile perch drove hundreds of cichlid fishes extinct

• current problem with introduced water hyacinth (plant) from S. America

largest lake in Africa

hyacinth: spread from 300 to 700Ha coverage in 2007

Nile perch

cichlid fish

Predation

Island of Guam

• brown tree snake (Boiga irregularis) introduced accidentally

•Species moved across the island, preying on and eliminating native birds, which evolved in the absence of predators and lacked the ability to fly

Predation

Competition

Zebra mussels (Dreissena) eliminated native unionid mussels from Lake St. Clair

Nalepa (1994) Can. Jour. Fish. Aquatic. Sci.

Zebra mussels swept from S to N in L. St. Clair, wiping out native mussels as they dispersed across the lake.

This followed population decline caused by human exploitation of the shells and predation by introduced biological control agents (another snail)

Cunningham and Daszak (1998) Conservation Biology

Parasitism

South Pacific snail Partula turigida driven extinct following infection with microsporidian parasite called Steinhausia

Human, Plant and Animal Diseases

• Cholera spread (e.g. Peru from India)

• West Nile Virus (spread by birds and mosquitoes)

• Dutch Elm disease (fungus arrived with beetles from Europe)

• Chronic Wasting Disease (affects cattle in Alberta)

• Infectious Salmon Anemia (came to farmed salmon in N.B. from Europe)

• SARS and HIV in humans

Disease

Dogwood anthracnose: wilt and death caused by Discula destructiva

Dutch elm disease (beetle transmitted fungus Ophiostoma ulmi, that kills American elm)

Economic Impacts

Along with irreplaceable losses to biodiversity - Billions per year from

• Lost agricultural productivity

• Lost forest productivity

• Lost recreational opportunity

Pimental et al. 2005. Ecological Economics 52:273-288.

Notable invasive species in Essex County

European starlinghouse sparrow Phragmites

purple loosestrife

zebra mussel

sea lamprey

emerald ash borer

1830

1850

1870

1890

1910

1930

1950

1970

1990

2010

0

25

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75

100

125

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Ricciardi (2006), Canadian Journal of Fisheries and Aquatic Sciences

Cum

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Invasive Species in the Great Lakes

Early dominance by plants, currently most new invaders are invertebrate animals

05

1015202530354045

1810

-183

9

1840

-186

9

1870

-189

9

1900

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9

1930

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9

1960

-199

0

1991

-200

5

Invasion History in Great LakesN

umbe

r of

Spe

cies

Fish

Algae

Plants

Invertebrates

Holeck et al. (2004), Bioscience

Invasion Vectors post-1959 (Seaway opens)

Ships are implicated in 75% of NIS invasions since 1959

(wind, waterfowl)

9

ships

13

Holeck et al. (2004), Bioscience

Asian Carp Are Poised to Enter the Great Lakes

1) Bighead Carp - 3 found in Lake Erie in 2000- sold live in Asian food markets in Toronto

2) Silver Carp

Our Lakes are Vulnerable

restrictions on sale of live fishes in Ontario since 2005

Ballast Water in Ships

• Ships loaded with cargo called are stable and do not need ballast water

• Ships without cargo carry ballast water to increase stability

• Probably the single biggest source of invasive species globally (when combined with hull fouling species)

Opening of the St. Lawrence Seaway 1959

with water from the 7 Seas of the world

...little did they know what they were doing

Welland Canal opened in 1959, allowing large ships into Lakes Ontario, Erie, Huron, Michigan

Nonindigenous animals established in the Great Lakes drainage since the mid-1980s

Common name Year of

Discovery

Endemicregion

Mode oftransfer

Probabledonorregion

RuffeZebra musselQuagga musselRuddRound gobyTubenose gobyNew Zealand mudsnailEchinogammarus amphipod

19861988198919891990199019911994

Ponto-CaspianPonto-CaspianPonto-CaspianEurasiaPonto-CaspianPonto-CaspianNew ZealandPonto-Caspian

Ballast waterBallast waterBallast waterBait releaseBallast waterBallast waterBallast waterBallast water

Danube RiverBaltic SeaBlack Sea--Black SeaBlack SeaBaltic SeaBaltic Sea

Sphaeromyxa sevastopoli protist 1994 Black Sea Ballast water Black SeaScolex pleuronectis cestode 1994 Black Sea Ballast water Black SeaIchthyocotylurus pileatus trematode1994 Black Sea Ballast water Black SeaBlueback herring 1995 Atlantic, N.A. Canal Atlantic N.A.Heteropsyllus nr. nunni 1996 Atlantic N.A. ? Atlantic N.A.Acineta nitocrae ciliate 1997 Eurasia Ballast water Black SeaCercopagis waterflea 1998 Ponto-Caspian Ballast water Baltic SeaDaphnia lumholtzi 1999 Africa Fish? Ohio ReservoirsSchizopera borutzkyi 1999 Ponto-Caspian Ballast water Danube RiverNitocra incerta copepod 1999 Ponto-Caspian Ballast water Black Sea 3 testate rhizopod spp. 2003 Ponto-Caspian Ballast water Eurasia Gammarus tigrinus 2003 Atlantic, N.A. Ballast water Atlantic N.A.

Invaders use ‘Corridors’ to the Great Lakes

Baltic and North Sea ports are major sources of ships for the Great Lakes; most of our invaders began in the northern Black Sea region

How can we determine where invasive species originated?

1. Track the vector: look at import: export records

2. Look at pathways that airlines & ships utilize

3. Assess at genetic composition of the populations in introduced areas and source areas

Eurasian distribution of the fishhook flea

• Native to Aral and Caspian Lakes, Azoz and Black Seas

• Introduced to several rivers and Baltic Sea

• Discovered in Lake Ontario in 1998

fishhook flea, Cercopagis pengoi

MacIsaac et al. (1999), Can. J. Fisheries and Aquatic Sciences

Cercopagis distribution

1998 1999 2001 2002

MacIsaac et al. (1999), Can. J. Fisheries and Aquatic Sciences

Cercopagis invasion genetics

mitochondrial ND5 gene

Hebert & Cristescu (2002), Can. J. Fisheries and Aquatic Sciences

Animal and protist NIS ‘hotspots’ in the Great Lakes

Ships discharge mainly into Lake Superior, yet most invasions are focused in the Huron-Erie corridor

Grigorovich et al. (2003), Canadian Journal of Fisheries and Aquatic Sciences

Spiny waterflea invasion history in Ontario

Year

MacIsaac et al. (2004), Ecological Applications

Ontario

Michigan

Ohio

Distribution of spiny waterfleas in Canada (2005)

Minnesota

+ 13 new reported invasions in 2006 N. Yan, pers. comm.

Invasion causes a decline in zooplankton diversity in Harp Lake, Ontario

80 85 90 95

7

8

9

10

11

12

Pre-invasion mean

Cru

stac

ean

Ric

hnes

s (s

pp.s

ampl

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Year

Dr. Norman Yan, York Univ.

spiny waterflea invades

Post-invasion mean

~ 20% loss in species richness

Waterflea infestations are a major nuisance for commercial fishermen on Lake Erie

Overland transport mechanisms

Bythotrephes:

• Fishing/Downrigger lines • Bait buckets• Live well water• Bilge water• Macrophytes attached to boat

What can be done?

Grigorovich et al. (2003), Canadian Journal of Fisheries and Aquatic Sciences