Structure and Inbreeding of an Isolated Population of Moose Using Reduced-Representation Whole-Genome Sequencing

Abstract

Anthropogenic habitat fragmentation and loss have increasingly isolated populations. Under isolation, individuals are more likely to inbreed and experience depression of population dynamics. The wolves of Isle Royale, an island on Lake Superior, experienced bone deformities and nearly faced extinction due to inbreeding, while the moose of Isle Royale have shown little sign of inbreeding depression. Previous genetic studies have shown that Isle Royale moose are more inbred than their source population and have likely experienced purging of strong deleterious alleles. To investigate population structure and level of inbreeding, we conducted the first reduced-representation whole-genome sequencing of this population using RAD-seq of 99 moose. We found that Isle Royale moose show little sign of population structure and are well-mixed. This study also confirmed that Isle Royale moose diverged from their source population and have likely experienced no to very little migration. Working with previously published Minnesota moose, we also found Isle Royale moose experience less effective recombination than their source population. Lastly, we observed weak associations of homozygosity with birth year and disease status, though we surprisingly see a slight positive association with lifespan and homozygosity once excluding individuals below reproductive age. This research adds to the growing literature on how isolated, moderate-sized populations evolve and persist in the absence of gene flow.