BIOL 4150 Lecture 8: Lecture 8
17 Feb 2012
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Distribution: distribution is explained by the balance between mechanisms that add individuals, and those that delete or limit them. Limits to distribution: (a) dispersal: fragmentation, allele effects, reduced gene flow (b) habitat selection: habitat loss (c) competition, predation disease: invasion, species loss. (d) physiology: tolerance thresholds climate change. Deleterious: mechanisms that decrease distribution (competition, predation, disease, abiotic thresholds, behavioral interactions) Different ways to get the same local distribution: Method: observation: settlement rates and mortality estimated by changes in unoccupied space, two species monitored. Finding: there"s room (mortality, inefficient capture of space, disturbance) : range and abundance = rate of settlement, not by competition. For a species to colonize a site it must both arrive there by dispersal from another site and maintain positive population growth in the local environment. Results: 91% failure, with successful individuals rare after three years, no significant change in diversity or productivity, reduced diversity in pond =increased establishment. H0: additions have no effect on diversity.
