Deciphering translocations from relicts in Baranof Island mountain goats: is an endemic genetic lineage at risk?

Abstract

Human-mediated movement of wildlife is a common practice in North America. Some translocations have occurred where local populations were thought to be extinct or simply not present. In Alaska’s Alexander Archipelago, mountain goats (Oreamnos americanus) were not considered indigenous and were introduced to Baranof Island in 1923. However, a range-wide survey using microsatellites and mitochondrial DNA revealed a distinct genetic subpopulation endemic to the island. In this study, we attempted to clarify the evolutionary history of the mountain goats on Baranof Island by examining sequence variation in the Y chromosome. We first screened five regions of the Y chromosome in a subset of mountain goats from across their native range. We detected a single polymorphic site in the SRY promoter, and subsequently sequenced this gene in 100 mountain goats. A unique Y chromosome polymorphism was restricted to Baranof Island and an area near Haines, Alaska, and not detected in the presumed source population. An island-to-mainland dispersal scenario from a cryptic refugial population during the retreat of the Cordilleran ice-sheet would account for this distribution. Overall, these data support the hypothesis that a glacial relict population of mountain goats was present on the island prior to introduction. Based on a combination of mitochondrial, microsatellite, and Y chromosome data, we recommend recognizing Baranof Island mountain goats as an evolutionary significant unit.