Invasive Species

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Invasive Species
Class 6 Presentation 1

• The biggest threat to biodiversity after habitat
  destruction

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Overview

• Impact
• Examples
• Summary of characteristics of invasive

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Definition

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

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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)

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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

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Alien agricultural and forest pests in Canada
2002 Report of the Commissioner of the
Environment and Sustainable Development
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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).

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Beech Bark Disease (Nectria coccinea var.
faginata)
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Dandelion
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Gypsy Moth (Lymantria dispar)
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Dutch elm disease (Ophiostoma ulmi)
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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

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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

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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
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Life History Characteristics of Agricultural
Invasive Plants

• Herbaceous
• Rapid reproduction
• Dispersed abiotically

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Life History Characteristics of Natural Area
Invasive Plants

• Aquatic or semi-aquatic
• Grasses
• Climbers
• Nitrogen fixers
• Clonal trees

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Life History Characteristics of Invasive Birds

• Dispersal ability
• High rate of population increase
• Large clutch size
• Several clutches/season
• Compete with native species

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Life History Characteristics of Non-Invasive
Organisms

• Lack of pre-adaptation to new environment
• Competition/Predation from native organisms
• Diseases

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Life History Characteristics of Invasive Fresh
Water Fish

• Tolerance to broad range of environments
• Rapid dispersal
• Aggressive behaviour
• Short generation time

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Other features

• Desired by humans
• Close association to human activity

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Summary

• Early germinators (gap grabbers)
• Competitors for resources
• Reallocate resources to growth/reproduction
• Survivors (resist death)
• Swampers (mass germinators)

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Genetics and Evolution

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

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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 ?

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Range Expansion

• Rapid expansion large amount of gene flow
• May constrain local adaptation