Invasives Exam Two

What is the paradox of invasion genetics?

Small founder populations with presumably low genetic diversity that are at high risk of extinction

Invaders go through a genetic bottleneck. What does this mean?

Severe reduction in genetic diversity occurring when a small number of individuals colonize a new area, taking only a fraction of their source population's genetic variation with them

What are 2 things invaders (should be) susceptible to?

1. Inbreeding depression

2. Genetic drift

Why is loss of genetic diversity a risk for population viability?

Genetic drift fixes common alleles and rare alleles are lost

diminishes capacity to adapt to environmental changes

Invader evolution:

Physiological or behavioral changes might be harder to think about, but changes in an invader's morphology are more obvious

ex: Cane Toad in Australia

Cane toads under positive selection to colonize new habitats:

Ones that get there first have little competition and move faster; ones that move faster have longer limbs

Native fauna under selection to resist the toxins in cane toads:

Australian black snake

other species have some behavioral changes

2 evolutionary changes due to selective pressures (Indian mongoose):

1. Lower investment in attractive structures (anal glands) that aren't necessary due to high encounter rates

2. Larger testes to generate higher sperm counts (response to sperm competition)

Genetic changes favoring range expansion (Johnsongrass):

Perennial in native habitat; moved northward with crops

developed new ecotypes: overwintering rhizomes and conversion to annual life history (seeds dormant through winter)

What are 3 frameworks for understanding why/how/when invaders evolve?

1. Enemy Release Hypothesis

2. (Darwin's) Novel Weapons Hypothesis

3. Evolution of Increased Competitive Ability Hypothesis

What is one of the most researched (and supported) hypotheses in the invasion ecology field?

Enemy Release Hypothesis

Enemy Release Hypothesis:

Invaders have such strong impacts because they left their natural enemies 'at home' (herbivores, parasites, pathogens); invaders are at an advantage when competing with native species

According to the Enemy Release Hypothesis, why do natives struggle with invaders?

They must spend a larger fraction of their resources defending against enemies (secondary chemicals, thorns) and still suffer substantial mortality and reduced reproduction; invaders are free from such costs and can devote more resources into growth and reproduction

counter to Elton's idea of biotic resistance (the novel community isn't 'putting up much of a fight')

One type of evidence to support the Enemy Release Hypothesis:

Fewer pathogens in naturalized range as opposed to native range

pathogens from naturalized range can consume novel host (some right away, some adapt to consume a newly dominant host)

(Darwin's) Novel Weapons Hypothesis:

Idea that 'weapons' (allelochemicals, toxins) are more potent against naive species

in absence of natural enemies, more resources can be devoted to pathways or end products that would enhance these novel weapons (ex: cane toad)

(Darwin's) Novel Weapons Hypothesis: Native Range:

1. Competitors have evolved with plant

2. 'Weapons' less effective as competitors have adapted to the plant

3. Competitive balance maintained

(Darwin's) Novel Weapons Hypothesis: Introduced Range:

1. Native competitors naive

2. Weapon effective

3. Competitive balance tipped

Evolution of Increased Competitive Ability (EICA):

Invaders free of natural enemies can divert resources away from defense and towards life-history traits that enhance their competitive abilities

EICA: Native range:

1. Natural enemies present

2. Invests in defenses

3. Resources to defense not available for growth/reproduction

4. Competitive balance maintained

EICA: Introduced range:

1. Natural enemies not present

2. Invests less in defenses

3. Increased investment in growth/reproduction

4. Competitive balance tipped

EICA example (Silene latifolia):

North American populations (1) invest less in trichomes on female calyx (2) grow faster (3) produce more flowers

What are 4 major reasons for people intentionally introducing animals?

1. Food

2. Sport

3. Pets

4. Ecosystem services

Intentional introduction for food example:

Asian snakehead, from NYC to pond in MD to Potomac

Intentional introduction for sport example:

European wild boars, mallard, red wigglers, etc.

Intentional introduction for pets example:

Boa constrictor in FL

Intentional introduction for ecosystem services example:

Australian dung beetle Project and USDA

What is biocontrol?

Introducing a natural enemy of an unwanted pest species with the expectation that the enemy will serve to reduce the population to a level that is not harmful

can be useful, but must be selective

ex: multicolored lady beetle

What are 5 major reasons for intentionally introducing plants?

1. Feed for livestock

2. Fiber

3. Erosion control

4. Food/habitat for wildlife

5. Horticultural trade and acclimatization societies

Intentional introduction for livestock feed example:

Johnsongrass

Intentional introduction for fiber example:

Monterey pine and douglas fir

Intentional introduction for erosion control example:

Kudzu

Intentional introduction for food/habitat for wildlife example:

Bush/amur honeysuckle

Intentional introduction for horticultural trade and acclimatization societies example:

Scotch broom by Thomas Jefferson

What are stepping stones?

Species are deliberately moved long distances to sites where they aren't highly problematic, but from these locations the species can move further along to nearby regions and then become invasive

Stepping stone example:

Eurasian collared dove was first brought to Bahamas and Lesser Antilles as a cage bird, but birds that escaped or were released, dispersed to FL by 1980s

How do unintentional introductions occur?

Many transported unintentionally as by products of the intended goods and services

Unintentional introduction as byproducts example:

Transport in ballast water (zebra mussel and Chinese mitten crab)

What are 2 impacts of invasions on humans?

1. Money

2. Public health

Median economic losses caused by invaders:

1.4% of GDP

Public health impacts of invasions example:

*Mosquitos: yellow fever (Africa to New World) and malaria (worldwide)

*Rodents: bubonic plage and cholera

Predicting invasions:

While introductions can be unpredictable (movement, reproduction), prediction is still needed (life history traits, biotic resistance)

What are 3 components of a management plan for invasive species?

1. Horizon scanning

2. Risk assessment

3. Risk management

Horizon scanning:

A systematic search to identify species that pose potential threats before they are introduced to a novel ecosystem

proactive approach

What are the 2 questions to answer for horizon scanning in invasive species management?

1. Risk assessment: how bad might it be?

2. Risk management: what, if anything, can be done about it?

5 steps for generating a risk assessment:

1. Identify the threats

2. Decide who might be affected and how

3. Analyze the risks and decide precautions

4. Record your findings and generate risk summary

5. Review and monitor

2 things a good risk assessment should do:

1. Estimate the probabilities of introduction, establishment, spread, and impact

2. Predict future distribution using species distribution models

Using risk assessments to create species distribution models:

Based on correlations relating current distributions of species suites of environmental variables to forecast a future distribution space

General assumption of species distribution models:

A species' fundamental niche (range of environmental conditions that constrain its range distribution) is primarily due to the abiotic environment (physiological constraints)

realized niche is solely a consequence of the abiotic environment

What do species distribution models not account for?

Species interactions (competition, predation, mutualism) that in combination with the physiological constraints described by the fundamental niche result in the realized niche

also doesn't account for adaptations

What is the most successful and cost-effective management option?

Prevention

minimize propagule pressure and probability of introduction

eradication is the next best option

6 factors for when eradication is feasible:

1. Sufficient resources/funding

2. Lead agency needs clear lines of authority to carry out procedures

3. Biology of target organism must make it susceptible to control procedures

4. Reinvasion must be prevented

5. Pest must be detectable at relatively low densities

6. Lead agency must anticipate collateral damage to other species and the ecosystem and be prepared to mitigate/restore

Steps in invasion process and relationship with management:

*Prevention: native elsewhere, survival in transport

*Eradication: establish in new areas, lag period

*Control/Restoration: spread, ecological impact, human impact

What are the 2 main inspirations for enacting invasive species legislation?

1. Ecological impacts

2. Economic impacts

What country has not ratified the provisions of the Convention on Biological Diversity?

United States

What are the 3 main goals of the Convention on Biolgical Diversity?

1. Conservation of biodiversity

2. Sustainable use

3. Fair and equitable sharing of benefits of genetic resources

Goal of the Convention on Biological Diversity:

As far as possible, each signatory nation shall prevent the introduction of, control or eradicate those alien species which threaten ecosystems, habitats, or species

Weakness of the Convention on Biological Diversity:

The vagary of "as far as possible" and "as appropriate"

interpretations and regulations vary greatly across members

What are 2 problems of international agreements?

1. Individual nations are left to implement directives

2. Agreements can 'lack teeth' (while penalties might be possible, they aren't enforced)

What are 2 Clinton-era international treaties that have caused conflict with international agreements about invasive species?

1. World Trade Organization (WTO) (1995)

2. North American Free Trade Agreement (NAFTA) (1992)

What is the conflict with the Clinton-era international treaties?

They both require that any attempt by a signatory to exclude a shipment from another nation must be accompanied by a quantitative risk assessment validating that an economically or ecologically harmful invasion might ensue

Why are quantitative risk assessments hard to provide?

Lack of data, unpredictable ecological interactions, complexity of modeling across varied environments

rely on subjective expert opinion rather than data

so, inhibiting transport of invaders is extremely hard to do

What is one 'test' case for the international treaties conflict, and what were the results?

Australia tried to exclude frozen salmon shipment from Canada due to worry of parasites that would infect native fish; WTO ruled that Australia failed to produce a quantitative risk assessment; Australia was forced to either accept shipment or suffer a financial penalty

Black list:

Species on this list are prohibited

White list:

Species on this list are allowed

Gray lists:

Isn't enough information to make clear determination

often means species is prohibited pending further review

Why is New Zealand the gold standard for invasive species management?

No species whatsoever can be imported deliberately without prior consideration of an expert committee with no blanket exceptions (e.g. pets, crops)

2 laws in New Zealand regulating introduction of invaders:

1. Biosecurity Act

2. Hazardous Substances and New Organisms Act

establishes strong framework for keeping out potential invaders and for responding rapidly when an incipient invasion is detected

Australia's approach to invasive species management:

Relies heavily on risk assessments and requires risk assessments for species already in the country if the new introductions come from another source/location

utilizes black/gray lists

Why do island nations have advantages in regulating invasions?

They generally have centralized pathways for entry

borders = decentralized transport

What are 2 reasons why countries of larger geographic size have a harder time regulating introductions (e.g. Australia)?

1. More pathways and ports

2. Species native to one area aren't native in another, so there's greater potential for native invasions

What is the legislation that created a black list for the importation of animals into the U.S.?

Lacey Act (1900)

maintained by U.S. Fish and Wildlife Service (USFWS)

At what point in the invasion process are species generally added to the U.S. black list?

Generally, after they have already invaded

*house sparrow, starling, zebra mussel, Chinese mitten crab)

What is the legislation that created a black list for the importation of plants into the U.S.?

Plant Protection Act (2000)

previously Federal Noxious Weed Act of 1974

contains ~100 species, most of which are already present

National policies in both the U.S. and the European Union have both been reactive vs. proactive.

Economic externalities regarding invasive species:

Invasion are a consequence of market transactions but aren't considered by those engaged in the transactions

if damage occurs from an invasion, someone else (stakeholder) ends up bearing the cost (not the exporter or importer)

Strategies for internalizing economic externalities:

Could be done via tariffs on trade in living organisms or on pathways that carry them

strategies will be reactive or proactive

4 reactive strategies to internalize economic externalities:

1. Importers required to buy insurance against possible future damages if organism becomes a damaging invader

2. Importers bonded in order to be certain that funds would be available for eradication if organism becomes a damaging invader

3. Civil fines imposed on importer if organism becomes a damaging invader

4. Criminal penalties/fines levied on importer if organism becomes a damaging invader

2 proactive strategies to internalize economic externalities:

1. Fees imposed if importer is introducing a species

2. Taxes imposed on importers as a class