Lampyris noctiluca isolate:not applicable | breed:not applicable Genome sequencing. Lampyris noctiluca isolate:not applicable | breed:not applicable

Differential dispersion between the sexes can impact the colonization process and demographic history of a species. Here we explored the demographic history of the big European firefly, Lampyris noctiluca, which exhibits female neoteny. L. noctilucas distribution extends throughout Europe, but nothing is known about its colonization process. To investigate its demographic history, 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 resequencing data 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 farther western European population, followed by a 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.