Sex-biased migration and demographic history of the big European firefly Lampyris noctiluca

Differential dispersion between the sexes can impact population structure and connectivity between populations, which in turn, can have an effect on the evolvability capability of a species. Here we explored the demographic history of the big European firefly, Lampyris noctiluca, which exhibits female neoteny. L. noctiluca distribution extends throughout Europe, but nothing is known on how its colonization processes. To investigate this, we produced the first Lampyris genome (653Mb), including an IsoSeq annotation and the identification of the X chromosome. We collected 115 individuals from six populations of L. noctiluca (Finland to Italy) and generated whole genome re-sequencing for each individual. We inferred several population expansions and bottlenecks throughout the Pleistocene that correlate with glaciation events. Surprisingly, we uncovered strong population structure and low gene-flow. We reject a stepwise, south to north, colonization history scenario and instead uncovered a complex demographic history with a putative eastern European origin. Analyzing the evolutionary history of the mitochondrial genome as well as X-linked and autosomal loci, we found evidence of a maternal colonialization of Germany, putatively from a western European population, followed by male-only migration from south of the Alps (Italy). Overall, investigating the demographic history and colonization patterns of a species should form part of an integrative approach of biodiversity research. Our results provide evidence of sex-biased migration which is important to consider for demographic, biogeographic and species delimitation studies.