Lee-Yaw Julie A, Fracassetti Marco, Willi Yvonne (2017) Environmental marginality and geographic range limits: A case study with Arabidopsis lyrata ssp. lyrata. Ecography, in press
It is commonly assumed that geographic range limits of species reflect ecological niche limits and that species experience increasingly marginal conditions towards the edge of their ranges. Using spatial data and ecological niche models we tested these hypotheses in North American Arabidopsis lyrata. We tested whether range limits coincide with predicted niche limits and whether the suitability of sites declines towards the range edge. We further explored patterns of environmental change towards the edge of the range and asked whether genome-wide patterns of genetic diversity decline with increasing peripherality and environmental marginality.
Results suggest that latitudinal range limits coincide with niche limits. Populations experienced increasingly marginal environments towards these limits—though patterns of environmental change were more complex than most theoretical models for range limits assume. Genomic diversity declined towards the edge of the species’ range and with increasing distance from the estimated centre of the species’ niche in environmental space, but not with the suitability of sites based on niche model predictions.
Thus while latitudinal range limits in this system are broadly associated with niche limits, the link between environmental conditions and genetic diversity (and thus the adaptive potential of populations) is less clear.