Data from: History matters more when explaining genetic diversity within the context of the core-periphery hypothesis

The core–periphery hypothesis (CPH) predicts that populations located at
the periphery of a species' range should have lower levels of genetic
variation than those at the centre of the range. However, most of the
research on the CPH focuses on geographic distance and not on ecological
distance, or uses categorical definitions of core and periphery to explain
the distribution of genetic diversity. We use current climate data and
historical climate data from the last glacial maxima to develop
quantitative estimates of contemporary and historical ecological
suitability using ecological niche models. We analysed genetic diversity
using 12 polymorphic microsatellites to estimate changes in
heterozygosity, allelic richness and population differentiation in 31
populations of the wood frog (Lithobates sylvaticus) spanning the species’
entire eastern clade (33o to 45o latitude) from Alabama, USA, to Nova
Scotia, Canada. Our data support predictions based on the CPH. Populations
showed significant differences in genetic diversity across the range, with
lower levels of genetic variation at the geographic range edge and in
areas with lower levels of historical and contemporary ecological
suitability. However, history and geography (not current ecological
suitability) best explain the patterns. This study highlights the
importance of examining more than just geography when assessing the CPH,
and the importance of historical ecological suitability in the maintenance
of genetic diversity and population differentiation.