History matters more when explaining genetic diversity within the context of the core–periphery hypothesis

Abstract

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 (33(o) to 45(o) 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.

Environmental marginality and geographic range limits: a case study with Arabidopsis lyrata ssp. lyrata

“…In their review, Pironon et al () pointed out that such correlations are far from universal and suggested that colonization dynamics may play a more important role than ecological suitability in shaping patterns of genetic diversity. Similar conclusions have been reached by a number of studies for a variety of taxa (Soares et al , Duncan et al , Ortego et al , Pironon et al , Trumbo et al ). In A. l. lyrata clear support for an association between genomic diversity and range position, with only limited evidence of an association between genomic diversity and environmental suitability, suggests that colonization dynamics may have been the main factor shaping genetic diversity in this system as well.…”

The role of landscape and history on the genetic structure of peripheral populations of the Near Eastern fire salamander, Salamandra infraimmaculata, in Northern Israel

“…Hampe and Petit (2005) reviewed studies from the fossil record, phylogeography and ecology, and concluded that these low-latitude peripheral populations are disproportionately important for the survival and evolution of biota, yet these are the very populations that remain understudied despite having the highest chances for local extinction under climate change (Cahill et al 2013;Chen et al 2011). Second, there can be historical factors (Duncan et al 2015). For example, suppose past climatic conditions changed, resulting in a contraction of the species range but leaving isolated populations in favorable habitat islands in the previous range to create a zone of disjunct distribution.…”

Strong genetic differentiation but not local adaptation toward the range limit of a coastal dune plant

“…; Duncan et al. ). The correspondence between geographical range limits and niche limits, although rarely tested, is probably much weaker than expected (Hargreaves et al.…”

“…The drift and gene swamping hypotheses further assume that population demography across the range generally corresponds to the ACM (Brown 1984). However, the ACM is not well supported (Sagarin and Gaines 2002;Sagarin et al 2006;Sexton et al 2009;Abeli et al 2013), especially by range-wide demographic surveys (e.g., Samis and Eckert 2007), and alternative models have recently been considered (Abeli et al 2013;Martínez-Meyer et al 2013;Duncan et al 2015). The correspondence between geographical range limits and niche limits, although rarely tested, is probably much weaker than expected (Hargreaves et al 2014).…”