I. Exotic Species

• Species invasions may profoundly affect ecosystems• Definition?

• Criteria (Woods and Moriarty, 2001)1. Human introduction

• Direct vs. Indirect• Intention?• Is agency important?

2. Evolution• “Native”• How much does a species have to change?

3. Historical range• “Exotic”• How is a historical range determined/defined?

4. Degradation• How is “harm” defined? Some species harm & help

5. Community membership• What defines a “community”?

I. Exotic Species

• Species invasions may affect ecosystems profoundly

• Detrimental exotic species usually are• Superior competitors

• Ex – European starling• Effective predators

• Ex – Cane toad

Distribution of cane toad in AustraliaWikipedia

I. Exotic Species

A. Zebra mussel• Competitor in Great Lakes and elsewhere• Transported from Europe in ballast water• Fouling organism

• Restricts movement of water through intake pipes

• Colonizes boat hulls, pier pilings, buoys, etc.• Fouls other organisms (clams, mussels)

• Filter feeder – removes larvae and particulate material• Outcompetes native shellfish species for food

and space• Removes larvae from water

I. Exotic Species

B. Mongoose• Predator in Hawaii, Caribbean, etc.• Introduced to HI in 1883 to combat rats and

snakes in sugar cane fields• Reproduce early and rapidly

• Females can breed at 10 weeks, 2-3x a year, 2-3 young per litter

• Prey on native birds, amphibians, reptiles

Nile perch – Lake Victoria Brown tree snake - Guam

Argentine ants - California Caulerpa taxifolia - California

I. Exotic Species

• May be especially detrimental to biodiversity and ecosystems when populations of keystone species are reduced or eliminated

I. Exotic Species

• Are all exotic species bad?

• What should we do about exotic species?

• Ex: Eucalyptus in California