Invasive Species

The biggest threat to biodiversity after habitat destruction

Class 6

Presentation 1

Overview

• Impact

• Examples

• Summary of characteristics of invasive

Definition

Organisms (usually transported by humans) which successfully establish themselves in, and then overcome, otherwise intact, pre-existing native ecosystems (World Conservation Union (IUCN)).

Impact

• Economic impact: billions of dollars/year (See next slide)

• Impacts on biodiversity• Research/Regulation/Control/

Management • 30,000 non-native spp in N Am

since colonization• 30% of 4,200 vascular plant spp in

Canada exotic (not all invasive)

African land snail (Achatina fulica) in Florida

• 3 snails smuggled in by boy returning from Hawaii in 1966

• Grandmother released them in her garden• Problem noticed in 1969

– Mailed info to 150,000 houses– Infestations found 25 km outside initial area– Eradication program started, 18k snails found– Cost US $1 million

2002 Report of the Commissioner of the Environment and Sustainable Development

Alien agricultural and forest pests in Canada

How do they get around?

• Aquatic: ballast tanks in ships (simple solution to eliminate problem: exchange water at sea)

• Non-deliberate: most linked to human activity• Deliberate:

– soil erosion prevention = kudzu

– Feel like home: birds and game fish

– Some related to agriculture, ornamentals, captivity (e.g. aquarium trade).

Beech Bark Disease (Nectria coccinea var. faginata)

Dandelion

Gypsy Moth (Lymantria dispar)

Dutch elm disease (Ophiostoma ulmi)

Life History Characteristics of Invasive Species

• Plants

– Reproduce sexually and asexually

– Self fertilization

– Lack of seed pre-treatment for germination

– Long period seed on plant

Can we detect invasiveness?

• Early attempts to look for life traits of a species that would link that spp with potential invasiveness have failed. Why?

• Best bet is to study those that have become invasive = high probability for being invasive in another similar ecosystem

Life History Characteristics of Invasive Species

• Exotic spp often have fewer infections and predators.

• Drop in all diseases amoung European plants in N Am: 77%

• Ave # of parasites in home range: 16

• Ave # parasites in new range: 3

D. Pimental et al, Nature, Feb 6, 2003

Life History Characteristics of Agricultural Invasive Plants

• Herbaceous

• Rapid reproduction

• Dispersed abiotically

Life History Characteristics of Natural Area Invasive Plants

• Aquatic or semi-aquatic

• Grasses

• Climbers

• Nitrogen fixers

• Clonal trees

Life History Characteristics of Invasive Birds

• Dispersal ability

• High rate of population increase– Large clutch size– Several clutches/season

• Compete with native species

Life History Characteristics of Non-Invasive Organisms

• Lack of pre-adaptation to new environment

• Competition/Predation from native organisms

• Diseases

Life History Characteristics of Invasive Fresh Water Fish

• Tolerance to broad range of environments

• Rapid dispersal

• Aggressive behaviour

• Short generation time

Other features

• Desired by humans

• Close association to human activity

Summary

• Early germinators (gap grabbers)

• Competitors for resources

• Reallocate resources to growth/reproduction

• Survivors (resist death)

• Swampers (mass germinators)

Genetics and Evolution

• Good source of research on genetics and evolution– Rapid directional selection– Hybridization (interspecific or previously

isolated populations)

Genetics and Colonization

• Pre-adaptation important

• Adaptive evolution also important

Rate of change to natural selection proportional to amount of additive genetic variation present

Multiple introductions: genetic diversity

Range Expansion

• Rapid expansion: large amount of gene flow

• May constrain local adaptation