6 - Ecological factors in population persistence

16 bio 3115 universit dottawa university of ottawa

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Unformatted text preview: logy Population size and the importance of different sources of uncertainty For very small populations, genetic and demographic uncertainty have large impacts on population viability while for larger populations, only environmental uncertainty and catastrophes are usually important. Population size Source < 100 100-2500 >2500 Genetic Demographic Environmental Catastrophes Impact M6.17 BIO 3115 Université d’Ottawa / University of Ottawa Cumulative extinction risk and sources of uncertainty In general, the cumulative impact of several different sources of uncertainty on extinction risk/population persistence is greater than the sum of individual effects. Thus, elimination of one of the risks may greatly increase chances of survival! Extinction risk Demographic Envt’l Both Source of uncertainty M6.18 BIO 3115 Université d’Ottawa / University of Ottawa M6.9 BIO 3115 Conservation Biology Computer simulation studies suggest that under demographic uncertainty, small increases in population size have increasingly large effects on persistence time, whereas under catastrophic uncertainty, increases in population size have increasingly small effects on persistence. Persistence Time (years) The relationship between persistence time and population size under different forms of uncertainty Demographic Environmental 200 100 Catastrophic Population Size of Mammals M6.19 BIO 3115 Université d’Ottawa / University of Ottawa What measurable attributes of a population can we use to predict, at least qualitatively, the likelihood of extinction? If there are good predictors, than we can use these predictors to help establish conservation priorities. What predictors of extinction risk are available to conservation biologists? Pop. 1 Pop. 2 Population attribute Extinction risk Good Poor predictor predictor Extinction risk Predicting extinction risk 1 2 Population M6.20 BIO 3115 Université d’Ottawa / University of Ottawa M6.10 BIO 3115 Conservation Biology Predictors o...
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