Landscape genetic connectivity and sex-specific responses in a range expanding damselfly

Range shifts induced by climate change have been documented in many insect taxa. The damselfly, Ischnura elegans, is undergoing a poleward range expansion in northern Europe showing local adaptation to environmental conditions at the range edge in Sweden. However,the role of neutral genetic connectivity and sex-specific responses in the range expansion process is unknown. We examine relative abundance, sex-specific landscape genetic relationships and morphological variation in I. elegans along a ~600km range expansion axis. We analysed 29 landscape resistance surfaces against genetic distances (FST and G`ST) calculated from 3,554 RAD seq-derived neutral Single Nucleotide Polymorphisms (SNPs) from 25 sites (n = 426 individuals). Resistance modelling showed cooler mean annual temperatures limited genetic connectivity linearly, with greater resistance at colder range limit sites. Relative site abundances were reduced along the sampled gradient; however,genetic diversity showed no significant change, suggesting recent colonisations. Results were consistent with female-biased dispersal, with females showing reduced temperature resistance to gene flow and a small, almost linear effect of land cover type that was not observed in males. Female, but not male, wing length also increased towards the range limit. Our findings demonstrate sex-specific morphological and landscape genetic responses during a climate-change induced range expansion.