title: Joint effects of population size and isolation on genetic erosion in fragmented populations: finding fragmentation thresholds for management.
abstract: Size and isolation of local populations are main parameters of interest when assessing the genetic consequences of habitat fragmentation. However, their relative influence on the genetic erosion of local populations remains unclear. In this study, we first analysed how size and isolation of habitat patches influence the genetic variation of local populations of the Dupont's lark (Chersophilus duponti), an endangered songbird. An information-theoretic approach to model selection allowed us to address the importance of interactions between habitat variables, an aspect seldom considered in fragmentation studies, but which explained up to 65% of the variance in genetic parameters. Genetic diversity and inbreeding were influenced by the size of local populations depending on their degree of isolation, and genetic differentiation was positively related to isolation. We then identified a minimum local population of 19 male territories and a maximum distance of 30 km to the nearest population as thresholds from which genetic erosion becomes apparent. Our results alert on possibly misleading conclusions and suboptimal management recommendations when only additive effects are taken into account and encourage the use of most explanatory but easy-to-measure variables for the evaluation of genetic risks in conservation programmes.
authors.affiliation: Estación Biológica de Doñana (EBD-CSIC) Sevilla, Spain.
authors.forename: María
authors.initials: M
authors.lastname: Méndez
authors.affiliation: Estación Biológica de Doñana (EBD-CSIC) Sevilla, Spain ; Department of Biology, University of Saskatchewan Saskatoon, SK, Canada ; Schulstrasse 47, 5423, Freienwil, Switzerland.
authors.forename: Matthias
authors.initials: M
authors.lastname: Vögeli
authors.affiliation: Estación Biológica de Doñana (EBD-CSIC) Sevilla, Spain.
authors.forename: José L
authors.initials: JL
authors.lastname: Tella
authors.affiliation: Estación Biológica de Doñana (EBD-CSIC) Sevilla, Spain.
authors.forename: José A
authors.initials: JA
authors.lastname: Godoy
keywords: conservation genetics; genetic diversity; habitat fragmentation; inbreeding; population genetics