Range-Wide Genomic Analysis of Pygmy Rabbits (Brachylagus idahoensis) Reveals Genetic Distinctiveness of the Endangered Columbia Basin Population

TL;DR

This study finds that the endangered Columbia Basin pygmy rabbit population is genetically unique and isolated, offering insights for conservation efforts.

Contribution

The study identifies specific SNPs for monitoring genetic rescue and reveals the genetic distinctiveness of the Columbia Basin population.

Findings

The ancestral Columbia Basin population shows the highest genetic distinctiveness.

Four distinct genetic groups were identified across the pygmy rabbit range.

SNP loci useful for tracking ancestry in the admixed CB population were identified.

Abstract

Background/Objectives: Pygmy rabbits (Brachylagus idahoensis) are closely associated with sagebrush steppe habitat across the western United States, and loss and fragmentation of this habitat has contributed to the near extirpation of the Columbia Basin population in Washington state (CB). The CB pygmy rabbit was listed under the Endangered Species Act in 2003, and recovery efforts have included captive breeding, reintroduction, and genetic rescue with the translocation of rabbits from populations across the species range. Methods: We used restriction site-associated DNA sequencing (RADseq) on samples from across the species range, including CB pygmy rabbits captured prior to genetic rescue and admixture. We determined population genetic structure across the pygmy rabbit range, tested for genomic signatures of adaptive divergence among populations, assessed the genetic distinctiveness of the ancestral CB population, and identified loci useful for monitoring ancestry in the current admixed CB population. Results: Our dataset included 9794 single-nucleotide polymorphisms (SNPs) across 123 individuals. We identified four distinct genetic groups, including the central portion of the species range and three peripheral populations: CB, northern Utah/Wyoming, and southern Utah. The ancestral CB population showed the highest degree of genetic distinctiveness using multiple clustering, ordination, and genetic differentiation analyses. We identified evidence for putatively adaptive variation among populations, but no significant gene ontology associated with local adaptation. Conclusions: Our results highlight the long-term isolation of the ancestral CB population as well as historical isolation of other peripheral populations. Our results also provide SNP loci for monitoring the consequences of genetic rescue efforts in the current admixed CB population.

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