EFB Exam 4

What are the 3 types of biocontrol?

Classical, augmentation, and conservation

Describe the classical type of biocontrol

It reunites invasive species with its natural enemies from its native range. It is a long term control.

Describe augmentation, a type of biocontrol

It is a release of a BC agent for short-term reduction in target pests. It comes in 2 flavors, inoculative and inundative

What is inoculative augmentation BC?

An agent is introduced proactively when pest populations are low. The enemy reproduces but eventually dies out.

What is inundative augmentation BC?

It is an agent introduced reactively when pest populations are high. The enemy does not reproduce. It is essentially a “biopesticide”

What is conservation BC?

It is a change or preserve habitat to favor the persistence and abundance of naturally occurring natural enemies. Usually native generalists.

What is classical BC?

It is most commonly used for invasive species because it is currently available, practical (economically and ecologically), and it is sustainable. It successfully maintains low population densities of widespread, well-established invasive species.

Define the characteristics of classical biocontrol (CBC)?

It involves the re-association of an invasive species with its natural enemy/enemies from its native range. High rate of failure, most attempts are unsuccessful. There is an element of risk, potential affects n non-target species. The return on investment is very high if successful.

What is the primary objective of classical biocontrol?

Biocontrol agent (BCA) reduces target invasive species to some “arbitrary” average level. Whatever the level is… reduces ecological harm, reduces economic harm, and maintains in perpetuity.

Eradication of the invasive species … BCA is linked … BCA population…

Is NOT an objective! It might occur occasionally at very local scales. BCA is linked to target invasive species. BCA population increases/decreases in sync with target species.

What are the challenges of developing classical biocontrol (CBC) programs

• Time consuming

• Expensive

• Might be cancelled at any stage

• Reaching step 8 does NOT guarantee successful control

What are the basic steps to developing and implementing a classical biocontrol program?

1. determining suitability / susceptibility of target organism for CBC

2. Survey native range for potential BCA’s

3. Evaluate ecology of potential BCAs

4. Select candidate BCA(s)

5. Conduct host range testing (secure release permission from APHIS)

6. Small scale experimental release

7. Large scale general release

8. Post release evaluation to determine establishment / impact

USDA Animal and Plant Health Inspection Service (APHIS) mandates steps … What is a draw back?

Steps 3-5 are mandated.

3. Evaluate ecology of potential BCAs

4. Select candidate BCAs

5. Conduct host range testing

A drawback is that it can take 5-10 years and millions of dollars.

How do we decide what to test?

With the centrifugal phylogenetic method (CPM).

What is the centrifugal phylogenetic method (CPM)

It is when plants are chosen to be tested from most closely related to more distantly related. It was developed originally for plants, now adapted for others.

How is the centrifugal phylogenetic method (CPM) used?

CPM is used to evaluate overall response and assign risk. Results lead to APHIS acceptance or rejection of BCA.

CPM…

• Includes crops and endangered species

• Often >50 species

• Exposed to potential BCA in No-Choice and/or Choice testing

Why is CBC of arthropods much less rigorous?

• Historically, people care less about non-target arthropods

• Protocols are less well-developed

Why is the CBC of arthropods much more difficult?

• Few potential BCAs are truly monophagous

• P’toids and predators often have complex behaviors, it is difficult to test in a lab

• Lab tests often over- or under-estimate host range

• Many natural enemies (especially predators) can learn and adapt to new environments / prey options

How do we measure CBC success?

• Often times it is NOT successful

• “Success” can vary greatly across taxa

What is the CBC success record for insects and plants?

Insects: success record is generally low

Plants: success record is pretty good.

CBC success against the invasive ________ is and exception

Homoptera (insect)

Why is host-range testing so important?

Host range testing is critical to determination of safety and it helps evaluate risk to non target species

How does host range testing work?

• No choice tests

• Choice Tests (1-choice, multi choice, and common garden)

What is a no choice test?

A no choice test is determined by genetics, and it informs our understanding of a BCA’s fundamental host range. A potential BCA is presented to a non target species in isolation. It eats or it starves to death. The degree of damage is measured as well as degree of development.

What are choice tests?

Choice tests are determined by many factors, and it informs our understanding of a BCA’s ecological host range

What is a one choice host ranging test?

A potential BCA is presented to non target species alongside the target species. It can choose what to consume.

What are multiple choice host range testing?

It is a potential BCA presented to multiple non target species alongside the target species.

According to the CBC steps, what does the suitability of invasive species to be controlled (step 1) question?

• Is the invasive normally controlled by specialist natural enemies?

• Is it susceptible to natural enemies?

• Is it of significant enough concern to justify the launching of a CBC program?

According to step 2 of the CBC steps, describe what surveying for natural enemies in native range questions?

It focuses on areas of native range with similar ecology/climate.

• Are specialist natural enemies present?

• Can they be collected?

• Is there a facility available to evaluate potential BCAs in native range?

According to step 3 of the CBC steps, describe what evaluating any discovered natural enemies question?

• Can they be reliably identified? Physiologically? Genetically?

• Are they a cryptic species complex?

• Do they appear monophagus or oligophagus?

• Are they suitable for climate in invaded range?

According to step 4 of the CBC steps, describe what selecting the most promising potential BCAs is?

• It demonstrates a limited host range in preliminary studies

• Can be reliably identified

• Seems to exert some control on target species in native range

• It is logistically feasible

According to step 5 of the CBC steps, describe why testing the host range of potential BCAs is important?

Organisms suitable for release as BCAs must be safe, effective, and logistically viable. It is required for approval in most countries.

Why is step 5 of the CBC steps a surprisingly recent addition to biocontrol programs?

• Negative publicity about the relative safety of biocontrol broadly

• Reducing the high failure rate of biocontrol programs

According to step 6 of the CBC steps, describe what small experimental release is?

• Limited numbers of BCA in semi-controlled field settings

• Careful, thorough, and short term observations

Assuming small scale release goes well, describe what step 7, large scale release of classical biocontrol is?

• BCA is collected or reared in large numbers

• Distributed throughout range of target invasive to partners/cooperators

• Distributed throughout range of target invasive to partners/cooperators

• Usually for free or at a cost

Describe step 8, post release / long term observation of classical biocontrol

It often doesn’t actually occur because it costs money and finding agencies already paid for the intervention s why keep paying to watch. It is very important to gauge if release actually worked.

Despite high failure rates, CBC is still one of our most important management tools because without it…

• Manage = perpetual mitigation costs

• Ignore = perpetual, compounding economic or environmental costs

• The few successful programs more than pay for the failures, very high cost: benefit ratios (about 1:145)

Biological control was viewed very positively by scientists and the general public for over 100 years. It was widely viewed as a “green” alternative such as chemical pesticides or insecticides. Few negative effects had been recorded at the cost of what important caveat?

The lack of obvious non target effects from biological control introductions might be misleading because until recently, few people had looked for them. AKA absence of evidence is not necessarily evidence of absence.

Which paper ignited a contentious debate about relative safety of CBC?

A seminal paper by Francis Howarth in 1983, known as Pandora’s Box

Howarths important premise was…

that biological control was far from safe and in addition to not working most of the time, was causing catastrophic non target effects

Why would no one seriously propose a generalist predatory for release anymore?

• Bad choice for biological control. It never targets specific, unpredictable, and it often learns how to hunt novel prey.

• Many of the worst non target examples of biological control involve predators

• Some have suggested that there has never been a generalist predator introduction that didn’t cause non target effects

Biological control of plants

• Non target effects from agents introduced for plants have generally had fewer non target effects

• Requirement for extensive host range testing and the restricted diets of many herbivorous insects have resulted in greater biological safety

What are some egregious examples of biological control plants?

Cactoblastis cactorum in NA as well as 3 species of thistle feeding weevils in NA, Australia, and NZ whose host range now includes an extensive number of non tarrget species.

Biological control of insects

• Most biocontrol programs against insects have utilized parasitoids

• Parasitoids are organisms that colonize a single host but mostly kill the host after they finish feeding

• Predators and pathogens are also used but to a much smaller degree

• 19% of insect control attempts using parasitoids have shown some non target use

• Much of the non target use is trivial (occurrence vs. impact)

• As in plant biocontrol, significant population-level impact on non target species appears rare

Bottomline on Biological Control is a vital tool in managing invasive species, but one with potential to improve, such as:

• Must develop better host range testing and risk assessment protocols

• Should streamline the approval/petition process

• Don’t have a way to evaluate evolution

• Host range testing inadequate for evaluation of species other than herbivorous insects

• Testing in artificial lab environments, which is necessary for contaiment, can overestimate or underestimate risk

• There is no such thing as a no-risk introduction

What does there is no such thing as a no risk introduction?

A successfully established species is a permanent addition to a region’s fauna: you functionally cannot undo a bad biological control introduction

Testing biocontrol in artificial lab environment, is necessary for containment, but can:

• Overestimate risk: leading to release of inappropriate agents

• Underestimate risk: leading to release of inappropriate agents

A critical area of biocontrol that needs reform is _______

The evaluation of risk.

Current risk analysis focuses solely on… This has led to … This often occurs in …

Current risk analysis focuses solely on whether the biocontrol agent will feed on a non target species. This has led to the rejection of many potential agents due to trivial feeding on nontarget species. This often occurs in no choice test which may not reflect host discrimination and selection in nature.

Biological control practitioners have pointed out that perception of risk is …..

being evaluated against the wrong metric.

Rather than asking what the risk of non target feeding is, we should be asking …

what the risk of doing nothing might be. For example, failure to introduce a BC species that had trivial nontarget effects should be weighed against the proliferation of an exotic plant that dominates ecosystems and outcompetes native species

Give an example of intraspecific cryptic invasion

The replacement of native Phragmites australis with a dominant European genotype of the same species

Define asymmetric gene flow

It is often the effects of hybridization or introgression between an exotic species and a native that have a far greater impact on the native species

Define allogenic

Ecosystem engineers that alter ecosystems by changing physical or structural components of the environment

The diversity/invasibility paradox focuses on

The divergent relationship between native and exotic species diversity with changing spatial scale

Define phenotypic plasticity

A genotype that produces different phenotypes under different environmental conditions

Define biotic resistance

The ability of species within native communities to prevent the establishment or spread of invasive species

The term invasional meltdown describes….

• Repeated invasions collectively weaken ecosystems making them easier to invade

• Synergistic relationships between 2 or more invasive species

Reduced population density and overall fitness of garlic mustard is negatively correlated with residence time in a community and may be driven by the acquisition of pathogenic soil fungi or other microbes, congruent with the _____

PAID hypothesis

Define followers

As residence time increases in a non native range, invasive species may begin to accumulate natural enemies from their own range

Describe what common garden is

A standard method for experimentally evaluating whether a given trait is plastic or genetically fixed

Define pull

Moving ecological analog species to novel areas to replace the functions of a lost native species

The effects of disturbance on invasions is often difficult to assess independently because of the combined effects of …

Propagule pressure

True/False: Whether an invasive species is born or made refers to a debate over intrinsic or extrinsic driver if invasion success

True

Some invasive species appear to have minimal impact on their environment despite being widespread and abundant because …

• They have replaced a native analog species

• They entered an unoccupied niche

If an invasive species success is attributable to enemy release …

• The invader is held in check by natural enemies in its native range

• In the absence of natural enemies, the invader can grow faster, produce more offspring, and/or compete better with native species

Genetic introgression is caused by

Repeated backcrossing with parent populations following hybridization

Maladapted populations characterized by a lengthy time lag after introduction can suddenly increase …

• de novo mutation

• Gene flow

What is the enemy release hypothesis invasion theory / EICA?

The idea that plant growth and plant defense represent a tradeoff in resource allocation

true/false: extinction debt may be why relatively few plant species have gone extinct exclusively from the effects of invasive species

True

Darwin’s novel weapons hypothesis states…

Invasive species are more likely to succeed if they have biological traits unique to the ecosystem that they have invaded

What are potential reproductive outcomes of hybridization between species? (5)

1. Offspring are inviable and it reinforces species boundaries

2. Offspring are infertile, which still use resources in the environment and represent lost reproductive effort which can be important when an abundant invasive is hybridizing with a rare native

3. Merge, two species become one

4. Hybrids preferentially mate with other hybrids or are incompatible with either parent populations creating a novel third species

5. Hybrids backcross with the parent species, leading to introgression

Invasion biologists often categorize invasive species as passengers or drivers. How do they differ?

• Driver species: species who presence can change the rules of existence for other species in an ecosystem. They are the disturbance

• Passenger species: those that take advantage of existing disturbances. Their success is dependent on a disturbance occurring from some external source.

Why do managers worry so much about driver species?

They are often ecosystem engineers. Their presence can modify ecosystems, changing the rules of existence for all other species in the ecosystem. They often facilitate invasions of other exotic species amplifying negative effects on the environment.

Populations of some introduced species spend years or even decrease at low population density before becoming problematic. How do you identify species whose populations are simply in the early phases of population growth from those that are exhibiting a time lag?

Populations characterized by time lags are better fit by a 2 part model where the population is characterized by no or very little growth until it suddenly takes off.

What are non genetic processes that can help a sleeper species escape constraint? (4)

• Climate change

• Disturbance

• Loss of a natural enemy

• Gain of a mutualist

What is an allee threshold?

An allee threshold is when there is a minimum population density (the threshold) where if population density is above, the population experience a positive per capita population growth rate up to some maximum value determined by the environment. Below the threshold, the population density is too low and population growth is negative, and the population will go extinct.

Why is an Allee Thresholds identification so important for managing new or isolated biological invasions?

Knowing or approximating the threshold value allows managers to determine whether an invasive population needs to be treated or left to go extinct on its own.

What is the important difference between a component Allee effect and a demographic Allee effect?

• Component: individual fitness increases with increasing population density. This may or may not have an effect on the per capita population growth rate. If the effect is weak, other factor could cancel out the benefit of higher population density on individual fitness

• Demographic: this is a population-level Allee effect. If sufficiently strong, increasing population density can result in growth of the entire population

Define ecosystem engineers. What are 2 reasons why we care the most about ecosystem engineers?

Many of the invasive species that have the greatest impact are those that are termed ecosystem engineers. Set of species whose impact is so profound that they affect most species in an ecosystem directly or indirectly.

1. Fundamentally change the rules of existence for all other species

2. Effects are often transformative and difficult to undo

With respect to invasions, hybridization between two invasive species (invasive x invasive or an invasive x native) can lead t unpredictable and challenging outcomes for managers, such as….

• May respond differently to environmental conditions or have broader tolerances

• Better competitors (grow faster or bigger)

• May be less susceptible to biological control

Only about 60% of studies support the enemy release hypothesis as an explanation for successful invasion. Describe 3 reasons why that could account for the failure of this hypothesis to explain successful invasions in many cases.

1. Native species adopt exotic species as hosts or prey

2. Exotic species are introduced with some of their natural enemy component

3. Many fail to take advantage of a lack of enemies because of other ecological constraints

How does the evolution of increased competitiveness (EICA) extend the enemy release hypothesis (ERH)?

In the ERH, absence of natural enemies results in greater growth/reproduction. In EICA, genotypes that allocate less to defense and more to growth/reproduction compete better and are favored by selection and become more common

How does the enemy release hypothesis (ERH) work?

1. Natural enemies are important regulators of the invasive species in its native range

2. In the introduced range, natural enemies will have a greater impact on native species than on the exotic species creating a competitive imbalance

3. With the reduction or absence of natural enemies, the exotic species can capitalize by increasing growth/reproduction, also creating a competitive imbalance

The introduction of Nile perch to Lake Victoria in the 1950’s ranks as one of the most damaging introductions in history. Describe 2 (direct or indirect) ways that this species changed this ecosystem permanently

1. Changed the traditional fishing economies

2. Caused the extinction of many endemic cichlid fish

What plays a role in establishment, the least understood part of the invasion process

1. Luck/chance

2. Propagule pressure

3. Biotic resistance

Define stratified diffusion

As invasions become larger, they often expand spatially through the coalescence of outlier populations with the main invasion front

What is the acronym for the US federal agency that is our frontline defense against incoming new invasive species

USDA APHIS

False positives are a potential issue with any sampling or monitoring metho for invasive species but are particularly problematic for …

Aquatic e-DNA samples

To reduce the importance of pallets, crates, and other low grade wooden shipping materials as vectors, signatory countries adopted an important standard known as …

ISPM 15

The rule of tens is not actually a rule at all a relatively few groups of organisms actually fit. A major departure from the predictions of this concept occur because …

Deliberately introduced taxa exceed the predicted rate

The live ornamental plant trade and exotic pet trade will continue to increase in importance as vectors because ….

• They are under or unregulated

• The volume and diversity of organisms moving is increasing

• Inspection capability has not kept pace with the diffuse nature of modern commerce

Propagule pressure is compromised of… (3)

• The number of independent introductions

• Number of individuals introduced

• An interaction between number introduced and number of introduced events

Malcom Mclean is most famous for …

Inventing the shipping container

An invasion pathway is

The route a species takes from its native to its introduced range

A genetic characteristic of populations with significant inbreeding is …

Higher levels of deleterious homozygous recessive traits