METAPOPULATION DYNAMICS AND EXTINCTION IN PRISTINE HABITATS - A DEMOGRAPHIC EXPLANATION

Abstract

Demographic and age-structured modelling of local populations in a pool frog (Pelophylax lessonae) metapopulation reveals that the natural emigration from a population is of a magnitude which, if all emigrants are lost from the system, enhances local extinction risk in comparison to if the emigrants become immigrants in other local populations. In the latter case, annual population growth rate averaged λ = 1.2, while in the former λ averaged 0.994. Simulations indicated that single local populations in pristine habitat with emigration and no immigration have an extinction probability of 0.532 in 100 years, with extinction occurring from 11 years after isolation and mean time to extinction of 61 years. Such isolated populations were also highly vulnerable to additive mortality. In comparison, two local populations interconnected by dispersal were resilient to increased and higher local mortality provided that connectivity and the source population of immigrants were unaffected. This provides a demographic explanation of extinction patterns observed in the pool frog and other taxa that likely has general relevance for the conservation and management of subdivided populations in various landscapes.