NRES 324 - Exam 2

weed risk assessment in AU

48 questions that grant non-problematic plants access into AU, is a black list approach

black list approach

innocent until proven guilty (not good for invasives, we have in the US)

Lacey Act black list approach reasoning

organisms will never be screened for invasiveness prior to importation due to slow pace of listing

Lacey Act white list

Attempted in the US but led to outrage by horticulture/pet trade. Passed by the House but not the Senate, difficult to enforce

What organizations helped required ballast water treatment?

UN International Maritime Organization and US Coast Guard

Ballast water treatments

UV irradiation, electrochlorination, ultrasound, ignores external hitchhikers (ex barnacles)

What organization does freight inspection?

Customs and Border Protection (CBP)

How can the transport of invasives be avoided?

a white list approach and shift in attitude

Why is funding surveys beneficial?

Eradication of nnsp is much more likely at earlier invasion stages before issues are caused

What tools have reduced the effect of area on nnsp eradication?

Drones, helicopters, ag and military technology

Goats of Galapagos

Killing first 90% was easy, last 10% very difficult. Now non-native blackberry is exploding

Why might a shrew have low susceptibility for eradication?

Refugia (tolerance to hard conditions), trap shyness, low trap efficiency, small

Steps to developing a biocontrol

Discovery, approval for import and study in USDA, quarantined studies, initial field release, monitoring and evaluation

Classic biocontrol approach

Release, biocontrol becomes naturalized, provides control. Risky

Periodic release biocontrol approach

Mass rearing of biocontrol agents, release, support an adventive population. Safer but more expensive

Conservation biocontrol approach

Attract and protect biocontrol agents

Main conclusion from a biocontrol meta-analysis

In plants biocontrols generally decrease the target species but most research doesn’t study what plants fill open niches or the structure of communities

pathogens as a biocontrol agent

Viruses, bacteria, fungi that are highly specific and can mutate or create resistance

predators/herbivores as a biocontrol agent

Easy to access, visible, mobile and effective. Many are generalists

parasitoid wasps as a biocontrol agent

Highly specific and small, quick spread

What is best to control invasive plants?

weevils, flies, true bugs, caterpillars, fungi

What is the best to control invasive vertebrates?

viruses, bacteria

What is the best to control invasive insects?

parasitoid wasps

Hydrilla

Dominated in FL, resistant to herbicides. Luck led to hydrilla miner and accidental release of asian hydrilla moth as controls

Mongoose

Controls rats in sugarcane plantations, on over 64 islands. A generalist that has led to extinctions, as was eradicated on small islands

What is the main takeaway from mongoose case study?

Conserving diversity is the idea that isolation drives speciation. Is it good to wipe out evolved mongoose lineages?

Alligator weed

Introduced via ballast water in FL, flea beetle, thrips, and stem borer are biocontrols. Still present at controlled low densities

Cane toad

Introduced to eat sugarcane pests, successful in some areas. Killed predators with toxicity in AU, efforts by locals and researchers failed

What is the main takeaway from the cane toad case study?

Predators are adapting to the toad by avoidance, birds learned toxic parts, snakes have smaller heads, ants can target the toads. Changing perception in AU through mascots and souvenirs

Purple loosestrife

Arrives through ornamentals and dry ballast. Can dominate wetlands (lack natural pests, EICA) but pollinators like it. Can cause more algae?

Asian lady beetles

Released as a biocontrol for aphids and other pests, can compete with natives by carrying a fungus that infects natives but not them, no known control

cactus moth

A biocontrol for prickly pear cactus in AU, effective until the moth spread to NA where there is native prickly pear cactus. Cannot be controlled because it lives with sensitive species

Gypsy/spongy moth

Released by scientist attempting to breed with silkworm moths, can spread by wind and defoliate hardwoods

WI biocontrols for the spongy moth

Fungus, Gypcheck virus, native parasitoid wasp that spreads with the moth

Yellow crazy ant

Nnsp on Christmas Island, alters ecology by killing red crab generalists. Have mutualistic relationship with invasive scale insects. Baiting is difficult, expensive, and not specific

assisted evolution

Puts controlled pressure on natives to produce a behavioral change, then meme evolution

meme evolution

transplant those aware of invasives hoping they’ll teach offspring

cobra effect

well intentioned measures often backfire and have the opposite effect (ex. farming invasives to get bounties)

Eating invasive species

Eliminates EICA since humans are the predators, harvest must be lethal and significant. Risks creating a market for nnsp, authority can fade, incorporation into local culture

Nontraditional biocontrol strategies

assisted evolution, bounties, eating invasives

Strategies to eliminate nnsp

Marketing is important, consider inaction for nnsp that are fun or will become a staple food item, don’t promise success when managing

Lake Tahoe Asian clam

Common nnsp filter feeder, assists in cleaning water but fouls beaches and may compete with native fingernail clam. Barriers and vacuums were tested and not feasible

Lake Tahoe signal crayfish

Introduced 4x as forage for fish and humans, native to CA (minor range extension), competes with native invertebrates and are food for invasive fish. Commercial harvesting allowed in certain places

Lake Tahoe Mysis shrimp

Native to midwest, added to lake as food for gamefish, increase algae by eating zooplankton, escape predation through daily vertical migration to deep waters. A random decrease increased Daphnia and water clarity

Lake Tahoe warmwater fish

Removal via electrofishing, effort in shallow water Tahoe Keys, hydra effect increased nnsp, fish are present due to plants. Although inefficient, electrofishing is still recommended

Plants in Lake Tahoe (curly leaf pondweed and milfoil)

Only a problem in shallow Tahoe keys, herbicide is controversial. Considered the largest threat due to habitat for warm water fish.

Benefits & cons of invasive plants

Competes with natives and look bad, improve water clarity by competing with algae, sequester nutrients near the Tahoe keys

Role of nutrient pollution in Tahoe keys

Grass clippings and irrigation, stormwater, sewer leaks, 55% of P and N from atmospheric deposition of vehicle exhausts

Attempted solutions for plants in Tahoe keys

Bubbles to dislodge plants, mechanical harvesting, UV-C light (doesn’t work good but still researching?), herbicides leading to algae blooms

Takeaways from Lake Tahoe

Nnsp = scapegoat for nutrient runoff, no realistic controls exist, misinformation regarding fish, exaggerated scope and severity of impacts, control efforts false/misleading

sterile insect technique

Rear and release sterile insects, wasted reproductive attempts decrease population, high effort but benefits outweigh costs (ex. native screwworm as an ag crop)

CRISPR

Highest risk=lowest control=highest reward. Can edit DNA in a heritable way (ex. mosquito in FL, malaria mosquitos, ticks), regulation is complex and public misunderstands responsibilities, fast forwards many conservation biology goals

gene drive

In offspring, an edited chromosome modifies the other and triumphs over other traits. Target genes are often sex-linked and can limit reproduction

super males

Lowest risk=highest control=less reward. Create and stock super males so that all offspring are male. Includes stocking nnsp to eliminate nnsp which leads to population collapse and Allee effect

Macquarie Island

A southern ocean island ringing Antarctica, has 20-40 researchers and land managers, tundra/grassland with very little diversity

Commercial history of Macquarie Island

fur seals, elephant seals for oil, penguins for oil

Macquarie Island (1800’s)

Mice, rats, and ship cats are introduced but annual patterns in prey abundance keep numbers low

Macquarie Island (1870-1900)

European rabbits introduced and ruin vegetation, cat population explodes and Macquarie parakeet goes extinct

Macquarie Island (1970-2012)

Rabbit virus eliminates 90% of pop., cats are eradicated and virus weakens. Rabbit, mice, and rat pop. explode and them are eradicated

How are rabbits, mice, and rats eliminated from Macquarie Island?

Aerial dispersion of rodenticide and intense hunting with dogs, when additional natives dies land managers persisted

Takeaway from Macquarie Island

This was the largest successful eradication of a natural area of an animal smaller than a goat

Myxomatosis

A natural host in SA and NA but kills most EU rabbits. Transmitted via mosquito and flea bites. Introduced to France, UK, Ireland, and Spain via a scientist that wanted to eliminate rabbits on his estate. Foresters and farmers appreciated him while hunters hated him