8 - Community interactions

L811 bio 3115 universit dottawa university of ottawa

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Unformatted text preview: ity of Ottawa Exotic introductions: the questions what effects, if any, do exotic introductions have on community structure and function? what are the characteristics of successful invaders? what are the characteristics of invadable communities? L8.12 Bio 3115 Université d’Ottawa / University of Ottawa M8..6 BIO 3115 Conservation Biology 3/11/2014 The ecological impacts of introductions negligible community effects elimination of one or more species through direct interactions (e.g. predation, competition) elimination of one species followed by other extinctions (“extinction cascades”) major changes in community structure and/or function. L8.13 Bio 3115 Université d’Ottawa / University of Ottawa The effects of exotic introductions: localized effects Exotic introductions effect a particular endemic species but otherwise have little or no effect. E.g. American chesnut, once a dominant species in NE North America, decimated by Chesnut blight (a fungus) introduced from China in late 1800s. Despite it being an important food source, no recorded vertebrate or Lepidoptera losses. L8.14 Bio 3115 Université d’Ottawa / University of Ottawa M8..7 BIO 3115 Conservation Biology 3/11/2014 The effects of exotic introductions: community composition Exotic introductions result in loss of a number of species from direct interactions, and a change in community composition. E.g. introduction of the brown tree snake to the island of Guam resulted in extinction of at least 10 species of endemic birds within 15 years through predation. L8.15 Bio 3115 Université d’Ottawa / University of Ottawa 1964: 10 1965: 10 1966: 10 1967: 9 1968: 10 1975: 9 1979: 9 1980: 7 1981: 6 1986: (1) Naval Communications Station (Swamp) 1965: 10 1975: 4 1986: (0) 1967:10 1980: 8 1968:10 1981: 6 1975: 10 1986: (1) 1979:10 1975: 8 1979: 5 1980: 4 1981: 3 1986: (1) Total loss: 10 endemic birds over a period of 15 years (Mangrove) 1966: 4 1967: 3 1968: 4 1969: 0 Cocos Island 5 km L8.16 Bio 3115 Université d’Ottawa / University of Ottawa M8.....
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