6 - Ecological factors in population persistence

4 bio 3115 universit dottawa university of ottawa m62

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Unformatted text preview: d’Ottawa / University of Ottawa M6.2 BIO 3115 Conservation Biology Goal: to estimate the Population Viability likelihood of extinction (population viability) over Analysis (PVA) some finite time period, given certain demographic, habitat and management parameters. Q1: Is there a critical N=20 minimum size below which the population faces N=100 imminent extinction? (the Minimal Viable Population or N=200 MVP) Q2: Is there a certain minimum viable area (MVA) of habitat needed to support Time (years) such a population? Probability of extinction M6.5 BIO 3115 Université d’Ottawa / University of Ottawa MVP(x, t) is the minimal viable population size required to ensure that the probability of population extinction within t years is less than 1- x (or the probability of persistence for t years is at least x). Often t is standardized to 100 years, and x to 0.95. Probability of extinction Population viability analysis N=20 N=100 N=200 Time (years) M6.6 BIO 3115 Université d’Ottawa / University of Ottawa M6.3 The larger the time period (t) over which extinction is assessed, the larger the estimated MVP (for constant x) The larger the persistence probability (x), the larger the estimated MVP (for constant t) x constant Time period (t) Estimated MVP The effects of time and extinction probability on MVP Estimated MVP BIO 3115 Conservation Biology t constant Persistence probability (x) M6.7 BIO 3115 Université d’Ottawa / University of Ottawa MVP and extinction forces Characteristics of the population or its environment which tend to “push” the population towards extinction, that is, decreases the likelihood of population persistence (increase extinction risk). The larger the sum of these forces, the larger the MVP. MVP Strong Persistence Sum of extinction forces Weak MVP/Persistence M6.8 BIO 3115 Université d’Ottawa / University of Ottawa M6.4 BIO 3115 Conservation Biology Estimating Minimal Viable Populations 3 approaches: Empirical determination of the size of populations that have persisted for a known period following isolation Through modeling population demography (based on r, per capita population growth rate, and V(r) due to demographic and environmental influences Determine the minimum population required to maintain most of the original genetic variability. M6.9 BIO 3115 Université d’Ottawa / U...
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This document was uploaded on 03/11/2014 for the course BIO 3115 at University of Ottawa.

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