Page # Invasive species Pop quiz. Invasive species. Invasive species. Endemic species - Species native to a particular area

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1 Pop quiz Put your name on one side of the card, and your 4-digit code on the other (5 points) On the side with your name, answer this question for 5 more points (10 points total extra credit): Define aposematic II. and their impacts Some definitions Endemic species - Species native to a particular area Exotic species - Species from somewhere else - Exotic species that establish, spread and pose a threat to endemic species

2 A. Global traffic The effects of global traffic aren t new Dogs and pigs from Portuguese ships finished off the dodo bird on Mauritius (1681) A. Global traffic But rate of mixing greatly accelerated by air travel For example starlings were introduced because someone had the great idea to import to the US all the birds from Shakespeare (1890) Gypsy moths were brought in to the U.S. because someone thought they might have potential for silk production (1800s)

3 I. Why do we have the problem? Saltcedar (Tamarix spp.) introduced as an ornamental shrub (1800s) And then there s the story of the cane toad, introduced from S. America to Hawaii and Australia (1930s) (video clip) Update on the cane toad Now in Kakadu, a World Heritage site Current research on use of a virus to carry in and express a gene lethal to cane toad development, and in disrupting breeding using female pheromone Are we done with these kind of mistakes? Don t bet on it Welcome to the World Plant Shop, the online home of Trans-Pacific Nursery. We offer rare, exotic, and unusual plants from all over the world, from the snows of Kilimanjaro and the Himalayas, to the rainforests of the Amazon, to the deserts of Australia and the woods of Appalachia.

4 Are we done with these kind of mistakes? Don t bet on it One of the plants featured on the World Plant Shop web site, kahili ginger (from India) Are we done with these kind of mistakes? Don t bet on it Kahili ginger in Hawaii, where it has been introduced with disastrous results (as well as in NZ) II. and their impacts Examples: 1) Purple loosestrife Introduced as ornamental in early 1800s, now in 48 states Invades wetlands, displaces birds, rare plants, threat to bog turtle, muskrat and mink II. and their impacts Examples: Red imported fire ants Accidentally introduced in 1920s Spread throughout SE U.S. and recently in CA and NM Now the target of a biological control program (more later)

5 II. and their impacts Examples: Red imported fire ants II. and their impacts Examples: Salt Cedar (Tamarix spp. ) Displaces native ant species -becomes an ant monoculture Large impacts on other invertebrates, small mammals Now distributed throughout most of the U.S. Major nuisance to agriculture, public utilities, to human beings II. and their impacts Examples: Salt Cedar (Tamarix spp. ) Serious problem in the arid west Grows along waterways, displaces native cottonwoods and willows Lowers the water table, changes the stream structure, increases soil salinity A. Intrinsic factors - related to species biology 1. High potential growth rate - a high r? Some studies find a correlation, others not 2. Dispersal ability E.g. Many plant invaders produce winddispersed seeds Species with close association with humans often get human -aided dispersal

6 A. Intrinsic factors - related to species biology 3. Reproductive mode Invasive plants more likely to be parthenogenetic, or self-compatible 4. Generalized, not specialized, ecological requirements (=broad niche) Species with mutualists or prey left behind won t spread, e.g. pollinators, mycorrhizal fungi, particular prey A. Intrinsic factors - related to species biology 5. Taxonomic identity Some orders, families, more likely to be invasive than others, even when corrected for the number of species in the group 5. Taxonomic identity Among plants, top invasive families: Poaceae (grasses), Asteraceae bamboo russian knapweed B. Context of the introduction 1. How many are introduced? 2. Climatic match What states in US would you predict to be most vulnerable? 3. Communities with vacant niches When invader uses resources differently than native species, e.g. mangroves invading Hawaii, social insects in New Zealand, placental mammals in Australia

7 III. What else makes a species invasive? C. Lack of natural enemies Most invaders are not pests in their country of origin Remember, most plant and animal populations are stable over time - even the cane toad in its natural habitat! Sources of mortality in country of origin, e.g. microparasites, macroparasites, and predators, are often lacking in new habitat C. Lack of natural enemies Example: The Argentine ant in the U.S. : the Argentine ant Argentine ant displaces native ant species How do they do it? A study by Holway (1999) looked at competitive mechanisms among 7 species of native ants with Argentine ant 1) Exploitative competition (efficiency of resource use) - Argentine ants found baits faster Argentine ant Time to find baits Other ants Time to recruit 10 workers

8 : the Argentine ant 2) Interference competition: One on one contests with Argentine ants were won with some species, lost with others : the Argentine ant 2) Interference competition However, in 6 of 7 species, Argentine ant colonies depressed numbers of native workers at baits - because colonies larger Before Argentine ants introduced and after they were removed While Argentine ants present Among the native ant species, there appears to be a life history trade-off between aggression (likelihood to win in interference competition) and search capacity (likelihood to win in exploitative competition) Argentine ants are here A. Do nothing Dominance rank (aggressiveness) Discovery, recruitment (search) Argentine ants seem to be free from this tradeoff- have more resources to spend on both. Likely because large colonies & no natural enemies Pros Very economical Cons Rarely solves the problem, which often gets worse!

9 B. Eradication by mechanical removal, pesticides Pros Can be a permanent solution to the problem if still very small populations Cons Can be difficult to judge when the population is too big, results in long term pesticide applications, negative ecological impacts C. Management by mechanical control, chemical control Pros May control the invader with enough persistence Cons Not usually a permanent solution. May be ecologically damaging, may not control the invader. D. Classical biological control - introducing natural enemy from country of origin Pros Can be a permanent solution with low environmental impact when an effective and highly specific natural enemy is chosen Cons Lack of specialization of natural enemy can lead to unintended ecological impacts. Biological control involving the introduction of vertebrate natural enemies has always been a disaster D. Classical biological control - introducing natural enemy from country of origin The cane toad example is one of the worst abuses of the practice of biological control Modern biological control agents are tested for specificity to the invader before being introduced

10 Biological control projects in progress Biological control projects in progress 1) Parasitic fly lays egg in head of fire ants Purple loosestrife Leaf chewing beetle Saltcedar (An unrelated) species of leaf chewing beetle 2) Fly develops, ant head falls off 2) Fly emerges from ant head Example of a classical biological control project Example of a classical biological control project Giant salvinia in New Guinea Floating water fern forms dense mat across lakes, canals Weevil introduced, dramatic reduction in Salvinia Specialist weevil and Salvinia stay at low levels

11 Example of a classical biological control project Giant Salvinia has more recently been found in the United States Biological control program now in progress Salvinia