Invasive species

Species extinction rates

Causes of Endangerment for Imperiled Species in the U.S. Wilcove et al (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 Pigs, goats, birds, sheep, crops “Friends” Accidental 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 Vehicle or carrier that is able to transfer species, or route of transmission Examples of vectors of invasive species 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) Unstable environment, density independent K (slow species) Stable environment, density dependent interactions Organism sizeSmallLarge Energy used to make each individualLowHigh # Offspring producedManyFew Timing of maturationEarly Late (with much parental care) Life expectancyShortLong Lifetime reproductive eventsOneMore 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

New Zealand Grey ( A. superciliosa superciliosa ) Hawaiian ( A. wyvilliana ) Florida Mottled ( A. fulvigula fulvigula ) Rhymer & Simberloff, 1996 Mallard ducks (Anas platyrhynchos) theyangpa.tripod.com/ Hybridization

Competition

Disease Asian songbirds host to avian pox and avian malaria

What do we do about invasives? Education, community support Prevention Quarantine, monitoring/early detection, emergency response Eradication Must be done early Need community support Control Ongoing, costly Containment, priority-site, biological control Biodiversity conservation Biotic resistance hypothesis (Elton 1958)

Some of the worst invaders MAMMAL brushtail possum (Trichosurus vulpecula) domestic cat (Felis catus) goat (Capra hircus) grey squirrel (Sciurus carolinensis) macaque monkey (Macaca fascicularis) mouse (Mus musculus) nutria (Myocastor coypus) pig (Sus scrofa) rabbit (Oryctolagus cuniculus) red deer (Cervus elaphus) red fox (Vulpes vulpes) ship rat (Rattus rattus) small Indian mongoose (Herpestes javanicus) stoat (Mustela erminea) REPTILE brown tree snake (Boiga irregularis) red-eared slider (Trachemys scripta) BIRD Indian myna bird (Acridotheres tristis) red-vented bulbul (Pycnonotus cafer) starling (Sturnus vulgaris) AMPHIBIAN bullfrog (Rana catesbeiana) cane toad (Bufo marinus) Caribbean tree frog (Eleutherodactylus coqui) **From – 100 of the world’s worst invasive alien specieswww.issg.org

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