A Selective Sweep across Species Boundaries in Drosophila

Abstract

Adaptive mutations that accumulate during species divergence are likely to contribute to reproductive incompatibilities and hinder gene flow; however, there may also be a class of mutations that are generally advantageous and can spread across species boundaries. In this study, we characterize a 15 kb region on chromosome 3R that has introgressed from the cosmopolitan generalist species Drosophila simulans into the island endemic D. sechellia, which is an ecological specialist. The introgressed haplotype is fixed in D. sechellia over almost the entirety of the resequenced region, whereas a core region of the introgressed haplotype occurs at high frequency in D. simulans. The observed patterns of nucleotide variation and linkage disequilibrium are consistent with a recently completed selective sweep in D. sechellia and an incomplete sweep in D. simulans. Independent estimates of both the time to the introgression and sweep events are all close to 10,000 years before the present. Interestingly, the most likely target of selection is a highly occupied transcription factor binding region. This work confirms that it is possible for mutations to be globally advantageous, despite their occurrence in divergent genomic and ecological backgrounds.

ON THE COYNE AND ORR-IGIN OF SPECIES: EFFECTS OF INTRINSIC POSTZYGOTIC ISOLATION, ECOLOGICAL DIFFERENTIATION, X CHROMOSOME SIZE, AND SYMPATRY ONDROSOPHILASPECIATION

“…comm.) and a recent analysis suggests a long history of range overlap for this pair (Brand et al ). (Counting sechellia and mauritiana as sympatric does not alter any of our conclusions, results not shown.)…”

Irrational exuberance for resolved species trees

“…; Heliconius Genome Consortium ; Brand et al. ), yet these loci control important adaptive characters. All of the calculations describing the expected proportion of discordant trees also assume no effects of selection.…”

How Do Species Interactions Affect Evolutionary Dynamics Across Whole Communities?

“…Recent work has documented HGT during colonization of acid mine drainage over several decades (Denef & Banfield 2012) (Figure 4), raising the possibility of tracking HGT over experimental timescales in field populations. 13 In eukaryotes, hybridization can either transfer adaptations between species (Brand et al 2013, Hedrick 2013, such as the spread of warfarin resistance between mice species (Song et al 2011), or create new phenotypes that thrive in novel environments, as in hybrids of Louisiana irises (Arnold et al 2012). Hybridization as a genetic species interaction could therefore enhance evolution in some circumstances.…”