| Popis: |
Hybridization may often be an important source of adaptive variation, but the extent and long-term impacts ofintrogression have seldom been evaluated in the phylogenetic context of a radiation. Hares (Lepus) represent a widespreadmammalian radiation of 32 extant species characterized by striking ecological adaptations and recurrent admixture. Tounderstand the relevance of introgressive hybridization during the diversification of Lepus, we analyzed whole exomesequences (61.7 Mb) from 15 species of hares (1–4 individuals per species), spanning the global distribution of the genus,and two outgroups.We used a coalescent framework to infer species relationships and divergence times, despite extensive genealogical discordance. We found high levels of allele sharing among species and show that this reflects extensiveincomplete lineage sorting and temporally layered hybridization. Our results revealed recurrent introgression at all stagesalong the Lepus radiation, including recent gene flow between extant species since the last glacial maximum but also pervasive ancient introgression occurring since near the origin of the hare lineages. We show that ancient hybridizationbetween northern hemisphere species has resulted in shared variation of potential adaptive relevance to highly seasonalenvironments, including genes involved in circadian rhythm regulation, pigmentation, and thermoregulation. Our results illustrate how the genetic legacy of ancestral hybridization may persist across a radiation, leaving a long-lasting signatureof shared genetic variation that may contribute to adaptation. |
