Invasive Species Lecture Notes

Flashcards about Invasive Species

Invasive species

Species that have become established in non-native ecosystems through human mediation and are permanent residents and breeding.

Established

In the context of invasive species, it means they are permanent residents and breeding.

General Problems of Invasive Species

Huge impact on biodiversity, reduction/extinction of native species, shifts in ecosystem structure, problems for humans (new pests/diseases), and high costs for agriculture/removal.

Common ways Invasive Species get introduced

Food, sport, accidental release/escape, attempted biological control or simply desire to have the species in the environment.

Traits of Successful Invaders

Generalists with wide natural range, habitat generalists, broad diet, rapid reproduction, low generation times, good dispersers, reproductive & genetic factors, taxonomic isolation, climate matching, and vacant niche.

Factors Facilitating Invasions

Lack of predators/parasites, topping up of the population, highly disturbed environments, simple food webs/ecosystems, and corridors to other locations.

The Tens Rule

Imported, introduced, established, and pest with roughly 10% escaping, 10% establishing and 10% becoming a pest

Problems Associated with Invasive Species

Predation, hybridisation/interbreeding, competitive displacement (and extinction), ecosystem disruption/reorganisation, and introduction of diseases/parasites.

Predation by Invasive Species

Some communities have few or no predators. Local species therefore are unused to dealing with them and are very vulnerable.

Hybridisation/Interbreeding by Invasive Species

Invasive species may hybridise with local species, so altering the gene pool. Hybrids may be fitter than either parent and dominate.

Displacement/Extinction by Invasive Species

Invasives in direct competition with other species may replace them in local environments and may ultimately lead to extinction.

Ecosystem Restructuring by Invasive Species

Invasives may alter the ecosystem to force out competitors/native species.

New Diseases Caused by Invasive Species

Local species are unlikely to have resistance to foreign parasites or diseases.

Control of Invasive Species

Control most effective if occurs early. Much cheaper too! Good invasives often breed and spread rapidly.

Biological Control of Invasive Species

Good control agents are very host specific (some parasites especially good for this reason). Some of the worst invasives are organisms originally introduced as control agents.

Economic Costs of Invasive Species

Prevention, containment, or eradication of invasives. Clear up / repair of damage from invasives: environmental damage and drought through to clogged pipes. Lowered production or destruction of crops / domestic animals. Effects on local wildlife / ecotourism etc.

Guam Case Study

Accidental introduction of the brown tree snake wiped out many native birds and drastically reduced the population of others.

Australia Case Study

Rabbits were introduced in the 1700s and spread rapidly, destroying crops and local vegetation causing severe erosion.

Myxamatosis

Introduced in the 1950s and reduced the rabbit population to about 20% of the previous total.

Conclusions about Invasive Species

Invasive species are major threats to almost all ecosystems. Small systems (e.g. islands) or those already disturbed are especially vulnerable.