Genetic diversity and population structure of the endangered saproxylic beetle L. cervus in a fragmented landscape

Abstract Despite the significance of saproxylic beetle species for ecosystems, the investigation of fine‐scale population genetics within the stag beetle, Lucanus cervus , remains notably limited. Because of their limited dispersal distances and habitat fragmentation, high genetic structure and low genetic diversity are expected in its populations. To evaluate the impact of habitat fragmentation on genetic diversity and structure, we examined 150 specimens of L. cervus from three sites in western Poland: two forest stands and one stand located in an Oak avenue. We utilised 19 microsatellite DNA loci for this examination. Results of neighbour‐joining analysis and principal coordinates analysis, values of differentiation indexes ( G' ST , D (Jost) and F ST ) and rare/private allele frequencies indicated weak genetic differentiation among individuals collected from the tree sites. A spatial component to the genetic structure was identified through STRUCTURE (LOCPRIOR), isolation by distance tests and spatial autocorrelation analysis. The genetic diversity remained relatively high (H E : 0.49–0.51), with no inbreeding observed and no significant differences in mean relatedness among individuals from sampling sites. Limited genetic differentiation between the individuals of L. cervus from the investigated sites may result from a lag time since fragment isolation, unrestricted gene flow and marker/sample size limitations. Though weak, the significant differentiation between two of the sites may be linked to environmental differences and distance. Genetic data support treating individuals from forests as a single management unit. Non‐invasive sampling suffices for genetic studies, but achieving balanced sampling is crucial for precise historical demography estimates of endangered species.