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Invasive species Species extinction rates Causes of Endangerment for Imperiled Species in the U.S. 100 90 80 70 60 50 40 30 20 10 0 Habitat destruction Non-native spp. Pollution Overharvest Disease Wilcove et al. 1998 (data from U.S. Federal Register) What are invasive species? Natives vs. non-natives Introduced Aliens Exotics Adventives/casuals Naturalized What are invasive species? Federal Government’s Executive Order defined as: an alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health Acceleration of introductions Rates of species introductions in Hawai’i Natural rate: 1 established introduction every 100,000 years After Polynesians: 1 established introduction every 50,000 years Since Europeans: 1 established introduction every 0.25 years, or 4 per year Approximately 1000 plant species established in the last 200 years out of about 5000 introduced History of the study of biological invasions Darwin’s Origin of the Species (1859) C. Elton’s book in 1958 Early 1980’s, biological invasions began to be recognized as problematic: call for assessment of scientific understanding In the early 90’s, invasions were still not given too much attention 1999 – BIG CHANGE An executive order required all federal agencies to refrain from activities that contribute to introduction and spread of invasives How do introductions happen? Most introduced species do not survive Of those that survive, many do not cause “severe harm” to native ecosystems, species or humans (only 15% of establishments) How do introductions happen? Intentional There is a perceived human benefit from introduction For example: Food “Friends” Accidental Pigs, goats, birds, sheep, crops Hitchhikers Insects and weeds Rats, mice How do introductions happen? Natural range expansion Ex: Barred Owls have moved westward into Spotted Owl range Prey Habitat Hybridization Invasiveness Undisturbed systems are not safe from invasion How do you know if a species will become invasive? Has it invaded elsewhere? Is the introduction within a range with similar environmental conditions? Vector? Continued vector? Vectors Vector Examples of vectors of invasive species Vehicle or carrier that is able to transfer species, or route of transmission Ships Visitors Other organisms Characteristics of good invaders Tolerant of wide range of environmental conditions Originate from area with diverse biota Generalist diet Ecological range overlaps with potential vectors Natural population controls not present For example: predators, disease, competition Abundant within large native range r selected life history traits Life History Traits r (fast species) K (slow species) Unstable environment, density independent Stable environment, density dependent interactions Organism size Small Large Energy used to make each individual Low High # Offspring produced Many Few Timing of maturation Early Late (with much parental care) Life expectancy Short Long Lifetime reproductive events One More than one Impacts of invasives Cost Ecological Ecosystem properties and processes Disturbance regimes Hydrology Native species loss Predation Hybridize- homogenization of unique regional biota Competition Disease Disturbance Regime Cheat Grass (Bromus tectorum) Hydrology American Beaver (Castor canadensis) Anderson et al. 2006 Impacts of invasives Cost Ecological Ecosystem properties and processes Disturbance regimes Hydrology Native species loss Predation Hybridize- homogenization of unique regional biota Competition Disease Predation Brown tree snake (Boiga irregularis) Introduced predators can alter community structure including trophic structure From Groom et al (2006) Predation Hybridization Mallard ducks (Anas platyrhynchos) theyangpa.tripod.com/ New Zealand Grey (A. superciliosa superciliosa) Hawaiian (A. wyvilliana) Florida Mottled (A. fulvigula fulvigula) Rhymer & Simberloff, 1996 Competition Disease Asian songbirds host to avian pox and avian malaria What do we do about invasives? Education, community support Prevention Eradication Must be done early Need community support Control Quarantine, monitoring/early detection, emergency response Ongoing, costly Containment, priority-site, biological control Biodiversity conservation Biotic resistance hypothesis (Elton 1958) Some of the worst invaders MAMMAL brushtail possum (Trichosurus vulpecula) goat (Capra hircus) macaque monkey (Macaca fascicularis) nutria (Myocastor coypus) rabbit (Oryctolagus cuniculus) red fox (Vulpes vulpes) small Indian mongoose (Herpestes javanicus) REPTILE brown tree snake (Boiga irregularis) red-eared slider (Trachemys scripta) BIRD Indian myna bird (Acridotheres tristis) starling (Sturnus vulgaris) domestic cat (Felis catus) grey squirrel (Sciurus carolinensis) mouse (Mus musculus) pig (Sus scrofa) red deer (Cervus elaphus) ship rat (Rattus rattus) stoat (Mustela erminea) red-vented bulbul (Pycnonotus cafer) AMPHIBIAN bullfrog (Rana catesbeiana) cane toad (Bufo marinus) Caribbean tree frog (Eleutherodactylus coqui) **From www.issg.org – 100 of the world’s worst invasive alien species The palila (Loxioides bailleui) Endangered Restricted population The palila (Loxioides bailleui) Food: mamane pods and flowers, native caterpillars in pods Introduced parasitic wasps (94% parasitism at lower elevational range of palila) The palila (Loxioides bailleui) Rats, mice, mongoose, feral cats, goats Alien grasses, increased fire risk