Unravelling the effects of contemporary and historical range expansion on the distribution of genetic diversity in the damselfly Coenagrion scitulum

Abstract

Although genetic diversity provides the basic substrate for evolution, there are a limited number of studies that assess the impact of recent climate change on intraspecific genetic variation. This study aims to unravel the degree to which historical and contemporary factors shape genetic diversity and structure across a large part of the range of the range-expanding damselfly Coenagrion scitulum (Rambur, 1842). A total of 525 individuals from 31 populations were genotyped at nine microsatellites, and a subset was sequenced at two mitochondrial genes. We inferred the importance of geography, environmental factors, and recent range expansion on genetic diversity and structure. Genetic diversity decreased going westwards, suggesting a signature of historical post-glacial expansion from east to west and the presence of eastern refugia. Although genetic differentiation decreased going northwards, it increased in the northern edge populations, suggesting a role of contemporary range expansion on the genetic make-up of populations. The phylogeographical context was proven to be essential in understanding and identifying the genetic signatures of local contemporary processes. Within this framework, our results highlight that recent range expansion of a good disperser can decrease genetic diversity and increase genetic differentiation which should be considered when devising suitable conservation strategies.

How connectivity shapes genetic structure during range expansion: Insights from the Virginia's Warbler

“…The number of generations presented here may seem low and may raise questions regarding our ability to detect the signature of a bottleneck or other effects of genetic drift. However, results from previous studies suggest otherwise (e.g., Garroway et al 2011, Harper 2011, Short and Petren 2011, Swaegers et al 2014. Our study provides evidence that continuous gene flow from conspecifics may prevent the loss of genetic diversity from recently established populations at the edge of a species' range.…”

“…Sakai et al (2001) suggested that maintaining genetic diversity in a recently established population is essential for successful establishment and growth of that population. Previous studies have found that new populations in recently colonized areas on the periphery of source populations exhibit fine-scale genetic structure, lower genetic diversity, and allelic frequency gradients in the direction of range expansion (e.g., House Swaegers et al 2014). Of the empirical studies referenced here, 4 of the 6 investigated genetic diversity and population structure in a species that underwent range expansion beginning in the 1990s, the same time period when the Virginia's Warbler was documented as having expanded its range into the Black Hills of South Dakota.…”

“…Similar patterns of loss of neutral genetic diversity should be found in contemporary range shifts, but since current climate changes are taking place more rapidly, the genetic changes occurring in populations undergoing current expansions should look aberrant when compared with populations in the center of a species' current distribution. Thus far, relatively few empirical studies have investigated the genetic responses of populations undergoing contemporary range expansions or distributional shifts (Garroway et al 2011, Song et al 2013, Swaegers et al 2014.…”

Genetic signature of the colonisation dynamics along a coastal expansion front in the damselfly Coenagrion scitulum

“…In this study, we performed a detailed spatiotemporal genetic analysis of the range expanding damselfly C. scitulum along a coastal axis during the first years after colonisation. The two novel key findings of the current study that extend previous insights obtained in the large‐scale study of this range expansion (Swaegers et al ., , ) are that (i) the spatial dynamics indicate founder effects and a major contribution from the broad expansion front during the colonisation of the coastline rather than a stepping‐stone colonisation process and (ii) the fine‐scale temporal dynamics do not reflect persistent founder effects and instead show considerable temporal instability in genetic indices.…”

Union of phylogeography and landscape genetics

“…For example, Swaegers et al (40,41), studying genetic diversity and structure of the damselfly Coenagrion scitulum, used a combination of mitochondrial gene sequencing, microsatellite analyses, and single-nucleotide polymorphisms across the entire species' range to disentangle the role of historical range expansions from the effect of recent range shifts due to global warming. Their multilocus polygenic analysis identified candidate loci potentially under thermal selection, and their studies highlight the usefulness of integrating genomic, phenotypic, and environmental data to disentangle historical and contemporary evolutionary and ecological processes.…”