Wiberg, R. A. W. | Search bioRxiv

bioRxiv2018

Genomic analysis of European Drosophila melanogaster populations on a dense spatial scale reveals longitudinal population structure and continent-wide selection

Genetic variation is the fuel of evolution, with standing genetic variation especially important for short-term evolution and local adaptation. To date, studies of spatio-temporal patterns of genetic variation in natural populations have been challenging, as comprehensive sampling is logistically difficult, and sequencing of entire populations costly. Here, we address these issues using a collaborative approach, sequencing 48 pooled population samples from 32 locations, and perform the first continent-wide genomic analysis of genetic variation in European Drosophila melanogaster. Our analyses uncover longitudinal population structure, provide evidence for continent-wide selective sweeps, identify candidate genes for local climate adaptation, and document clines in chromosomal inversion and transposable element frequencies. We also characterise variation among populations in the composition of the fly microbiome, and identify five new DNA viruses in our samples.

evolutionary biology↗

bioRxiv2018

Inter- and intra-specific genomic divergence in Drosophila montana shows evidence for cold adaptation

The genomes of species that are ecological specialists will likely contain signatures of genomic adaptation to their niche. However, distinguishing genes related to their ecological specialism from other sources of selection and more random changes is a challenge. Here we describe the genome of Drosophila montana, the most extremely cold-adapted Drosophila species. We describe the genome, which is similar in size and gene content to most Drosophila species. We look for evidence of accelerated divergence from a previously sequenced relative, and do not find strong evidence for divergent selection on coding sequence variation. We use branch tests to identify genes showing accelerated divergence in contrasts between cold- and warm adapted species and identify about 250 genes that show differences, possibly driven by a lower synonymous substitution rate in cold-adapted species. Divergent genes are involved in a variety of functions, including cuticular and olfactory processes. We also re-sequenced three populations of D. montana representing its ecological and geographic range. Outlier loci were more likely to be found on the X chromosome and there was a greater than expected overlap between population outliers and those genes implicated in cold adaptation between Drosophila species, implying some continuity of selective process at these different evolutionary scales.

genomics↗