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Data from: Combined evidence reveals the origin of a rapid range expansion despite retained genetic diversity and a weak founder effect

Bergman, Nora M12; Lehikoinen, Petteri3; Kluen, Edward12; Bensch, Staffan4; Lo Cascio Sætre, Camilla5; Eroukhmanoff, Fabrice5; Fossøy, Frode6; Procházka, Petr7; Smith, William J12; Stokke, Bård G6; Primmer, Craig R2; Thorogood, Rose12; Rönkä, Katja12

Published Sep 03, 2025 on Dryad. https://doi.org/10.5061/dryad.bcc2fqzrw

Data files

Abstract

Many species are currently experiencing range shifts in response to changing environmental conditions, but with potentially serious genetic consequences. Repeated founder events and strong genetic drift are expected to erode genetic variation at the range front, reducing adaptive potential and slowing or even halting the expansion. However, the severity of these consequences for the more common and highly mobile species undergoing environment-driven range shifts (c.f. invasions) is less clear. Here we combined historical observations of the common reed warbler (Acrocephalus scirpaceus) with contemporary movement data from ringing re-encounters and genomic (RAD-seq) data from across its European breeding range to (1) infer the origin and (2) quantify the genetic consequences of a recent and rapid northward range expansion. While there were no reductions in levels of nucleotide diversity or allelic richness, nor a signal of founder effect in the directionality index (ψ), our combined dataset approach was able to infer an expansion origin from the southwest. Furthermore, we found that private allelic richness retained a slight but significant linear decline along the colonisation route. These results suggest that high dispersal capabilities can allow even philopatric species to avoid the loss of genetic diversity during rapid range expansions. Nevertheless, if multiple lines of evidence enable identification of an expansion pathway, we may still detect genetic signals of expansion.