Invasive Species. We must make no mistake: We are seeing one of the Great historical convulsions in...

Invasive Species

"We must make no "We must make no mistake: We are seeing mistake: We are seeing one of the Great one of the Great historical convulsions in historical convulsions in the world's flora and the world's flora and fauna. We might say, fauna. We might say, with Professor with Professor Challenger, standing on Challenger, standing on Conan Doyle's 'Lost Conan Doyle's 'Lost World', with his black World', with his black beard jutting out: 'We beard jutting out: 'We have been privileged to have been privileged to be present at one of the be present at one of the typical decisive battles typical decisive battles of history‑‑the battles of history‑‑the battles which have determined which have determined the fate of the world.'" the fate of the world.'" C. S. Elton, C. S. Elton, The Ecology The Ecology of Invasions by Plants of Invasions by Plants and Animalsand Animals, 1958, 1958

Invasive problems in the U.S.

Lodge et al.• kudzu (Pueraria lobata) in the SE U.S.• cheat grass (Bromus tectorum) in western

U.S. crops and rangelands• zebra mussel (Dreissena polymorpha) in

the Great Lakes region• the seaweed caulerpa (Caulerpa taxifolia)• Asian longhorn beetle (Anoplophora

glabrapennis)• emerald ash borer beetle (Agrilus

planipennis)• sudden oak death (Phytophthora ramorum)• Viruses: West Nile, monkeypox, and SARS

Melaleucain S Florida

• Transpiration higher

• Lower water table

• Hotter fire• Deeper burn in

organic matter, more severe effects

Economic & other impacts to human

well-being• Forestry, agriculture• Boating, fishing, swimming,

water supply• Allergies, toxins• Fire: human life and property• Cost of control• Environmental cost of toxic

chemical use

Where did the invasive species problem come

from?• Why is the earth a loaded gun of biological invasions waiting to happen?

Darwin (1859):Darwin (1859):In considering the distribution of In considering the distribution of organic beings over the face of the organic beings over the face of the globe, the first great fact which globe, the first great fact which strikes us is that strikes us is that neither the similarity nor the neither the similarity nor the dissimilarity of the inhabitants of dissimilarity of the inhabitants of various regions can be wholly various regions can be wholly accounted for by climatal and other accounted for by climatal and other physical conditions…physical conditions…There is hardly a climate or condition There is hardly a climate or condition in the Old World which cannot be in the Old World which cannot be paralleled in the New…[yet] how paralleled in the New…[yet] how widely different their organic widely different their organic productions!productions!

Summary 1: Separate evolution in separate placesA global potential for invasionDarwin: Why separate creation for separate deserts

Is MORE SPP a problem?

The Homogocene’s Biodiversity EquationWhen does 1+1 not equal 2?Native Spp Alien Spp TotalComment/example

1 + 1 = 2 ComplementarityDaylilies?

1 + 1 = 1 CompetitionJapanese honeysuckle?

1 + 1 = <1 Changed processMelaleuca in FloridaMyrica in Hawaii

Where did the invasive species problem come

from?Part 2

Darwin (1859):

There is no exception to the rule that every organic being naturally increases at so high a rate, that, if not destroyed, the earth would soon be covered by the progeny of a single pair.The elephant is reckoned the slowest breeder of all known animals...[yet] after a period of from 740 to 750 years there would be nearly nineteen million elephants alive, descended from the first pair.

20,442 worlds of Paulownia

“Walker counted the seed in a Paulownia pod and found ‘almost exactly 2,000’. He estimated the number borne on the trees as over 21 million. If each developed into a plant, which produced the same number of seeds the next generation, in the third generation there would be plants enough to cover 20,442 worlds the size of ours (American Forestry 25: 1486. 1919).

Coker and Totten, Trees of the Southeastern States, 1945.

LOSSES: THE ROLE OF NATURAL ENEMIES

Douglas fir seeds --after Lawrence & Rediske 1962

100 Seeds dispersed47 At germination

21 3 month old seedlings8 One year old individuals

Where did the invasive species problem come

from?Summary 1 & 2• Evolution in isolation

producing adapted species which are unable to reach all appropriate sites

• All species can increase exponentially

THEREFORE the potential for invasions

is clear• BUT NOT ALL SPECIES ARE

INVASIVE• CAN WE EXPLAIN AND PREDICT

INVASIONS?• AN OUNCE OF PREVENTION IS

WORTH A POUND OF CURE…

What does science tell us about invasions and how might we use that

information in prevention? 5 invasion hypotheses

• 1a-d. Innate biology: Weediness, competitiveness, tolerance, preadaptation

• 2. Enemy release/Biotic resistance• 3a-c. Community invasibility:

diversity, productivity, disturbance

• 4. Availability• 5. Rapid evolution of invasiveness

2. Enemy release hypothesis (ERH)

Biotic resistance hypothesis (BRH)

Mitchell & Power 2003

Resources X Enemy ReleaseResources X Enemy ReleaseBlumenthal 2005. Science 310:243-244.Blumenthal 2005. Science 310:243-244.

Digression: Asia as a Digression: Asia as a source of invasive plants source of invasive plants & diseases& diseases

Close taxonomic relationship has its own problemsSpecialized pests & diseases

Chestnut blight, Dogwood anthracnose, Balsam & Hemlock woolly adelgids

MANY OTHERS!

THE COEVOLUTIONARY HYPOTHESIS Bounded variation among enemiesPersistence of the plant and its enemies results from a balance involving virulence, dispersal, and increase rate of the enemyANDdefense, dispersal, and increase rate of the hostBiological control tries to reestablish this coevolutionary context

What does science tell us about invasions and how might we use that

information in prevention? 5 invasion hypotheses

• 1a-d. Innate biology: Weediness, competitiveness, tolerance, preadaptation

• 2. Enemy release/Biotic resistance• 3a-c. Community invasibility:

diversity, productivity, disturbance

• 4. Availability• 5. Rapid evolution of invasiveness

5 invasion hypotheses:What to do

1a-d. Innate biology: Weediness, competitiveness, tolerance, preadaptation: SOME SPP ARE INVASIVE, PROHIBIT THROUGH RISK ASSESSMENT, DEVELOP STERILE CULTIVARS—YES

2. Enemy release/Biotic resistance: MANY SPP ARE INVASIVE, ESPECIALLY THOSE WITH HIGH GROWTH RATES AND HIGH RESOURCE DEMANDS, ASSESS ROLE OF ENEMIES—YES, but research is demanding

3a-c. Community invasibility: diversity, productivity, disturbance: SOME COMMUNITIES ARE INVASIBLE, MANAGE AGAINST INVASION, MANAGE AGAINST DISTURBANCE AND HIGH RESOURCE LEVELS, MANAGE FOR HIGH NATIVE RICHNESS—SOMETIMES, but not always feasible (disturbance, low richness, high resources are natural, too)

4. Availability: MOST SPP ARE INVASIVE, REDUCE AVAILABILITY—YES

5. Rapid evolution: RESTRICT GENETIC DIVERSITY—YES, but seems unlikely given horticultural interest in selection