Unexpected population genetic structure of E uropean roe deer in P oland: an invasion of the mt DNA genome from S iberian roe deer

Abstract

Introgressive hybridization is a widespread evolutionary phenomenon which may lead to increased allelic variation at selective neutral loci and to transfer of fitness‐related traits to introgressed lineages. We inferred the population genetic structure of the E uropean roe deer ( C apreolus capreolus ) in P oland from mitochondrial ( CR and cyt b ) and sex‐linked markers ( ZFX , SRY , DBY 4 and DBY 8). Analyses of CR mt DNA sequences from 452 individuals indicated widespread introgression of Siberian roe deer ( C . pygargus ) mt DNA in the E uropean roe deer genome, 2000 km from the current distribution range of C . pygargus . Introgressed individuals constituted 16.6% of the deer studied. Nearly 75% of them possessed haplotypes belonging to the group which arose 23 kyr ago and have not been detected within the natural range of S iberian roe deer, indicating that majority of present introgression has ancient origin. Unlike the mt DNA results, sex‐specific markers did not show signs of introgression. Species distribution modelling analyses suggested that C . pygargus could have extended its range as far west as C entral E urope after last glacial maximum. The main hybridization event was probably associated with range expansion of the most abundant E uropean roe deer lineage from western refugia and took place in C entral E urope after the Y ounger D ryas (10.8–10.0 ka BP ). Initially, introgressed mt DNA variants could have spread out on the wave of expansion through the mechanism of gene surfing, reaching high frequencies in E uropean roe deer populations and leading to observed asymmetrical gene flow. Human‐mediated introductions of C . pygargus had minimal effect on the extent of mt DNA introgression.

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