The Genetic Consequences of Matrix Models In Comparative Demography and Conservation Biology
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Enright, Nicole Marie
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Abstract
Comparative demography aims to expose the influence of fundamental life-history variables on the variability in species’ population structure. Classical approaches in comparative demography rely upon dissecting a stage transition matrix for populations and investigating the effect of each transition on population growth rate through elasticity analysis. This type of analysis has been implemented in a wide range of conservation biology studies to inform management decisions, but the genetic implications of increasing population growth through life-history perturbations has remained unstudied. In this study, elasticity analysis of matrix population models was extended to include the effects of life-history perturbations on effective population size and expected heterozygosity. This analysis was applied to a total of 25 taxa with different demographics. Species were divided into 4 life-history strategy categories to investigate the effects of life history strategy on elasticity of the finite rate of increase, λ, effective population size (Ne), and expected heterozygosity (He). A counterintuitive result indicated an increase in the life-history stage with the largest λ elasticity resulted in an increase in population size but a decrease in Ne for many species. The magnitude of this effect is strongest in species that are long-lived, and those with low fecundity. While increasing population size is a primary concern for populations at threat for extinction, genetic diversity must be maintained for the population to be viable. The simulation approach implemented here allows for a case-by-case examination of perturbing life-history and examining life-history dependent trade-offs. The current study indicates a need for conservation biologists to consider the genetic consequences of matrix modeling, especially in long-lived species and species with low fecundity.