Canadian polar bear population structure using genome-wide markers.

Evelyn L Jensen,Rute B G Clemente-Carvalho,Markus Dyck,Marsha Branigan,Peter V C De Groot,Kristen M Hayward,Christina Tschritter,Stephen C Lougheed

doi:10.1002/ece3.6159

Abstract

Predicting the consequences of environmental changes, including human‐mediated climate change on species, requires that we quantify range‐wide patterns of genetic diversity and identify the ecological, environmental, and historical factors that have contributed to it. Here, we generate baseline data on polar bear population structure across most Canadian subpopulations (n = 358) using 13,488 genome‐wide single nucleotide polymorphisms (SNPs) identified with double‐digest restriction site‐associated DNA sequencing (ddRAD). Our ddRAD dataset showed three genetic clusters in the sampled Canadian range, congruent with previous studies based on microsatellites across the same regions; however, due to a lack of sampling in Norwegian Bay, we were unable to confirm the existence of a unique cluster in that subpopulation. These data on the genetic structure of polar bears using SNPs provide a detailed baseline against which future shifts in population structure can be assessed, and opportunities to develop new noninvasive tools for monitoring polar bears across their range.

Highlights

Contemporary genetic population structure reflects the interplay between genetic drift, selection, and gene flow, which is modulated by climate, landscape, and population history
The previous studies included the global range of polar bears, and found that the genetic cluster of the Beaufort Sea continues around the arctic coast of Asia and Europe to the eastern side of Greenland (Malenfant et al, 2016; Paetkau et al, 1999; Peacock et al, 2015), which is why we have chosen to refer to this cluster in our study as the Polar Basin
There is congruence between our results based on thousands of genome-wide single nucleotide polymorphisms (SNPs) and previous studies using 16–21 microsatellite or ~3,000 SNP loci

Summary

Introduction

Contemporary genetic population structure reflects the interplay between genetic drift, selection, and gene flow, which is modulated by climate, landscape, and population history. A recently developed SNP chip for polar bears (Malenfant, Coltman, & Davis, 2015), used for a preliminary population structure analysis, revealed four genetic clusters in the Canadian Arctic; other than this no large-scale study has yet been published using genome-wide markers, there are focused studies at more local levels (Malenfant, Davis, Richardson, Lunn, & Coltman, 2018; Viengkone et al, 2016). Polar bears show a pattern of isolation-by-distance at both population and individual levels (Campagna et al, 2013; Paetkau et al, 1999) within these distinct genetic clusters in the Canadian Arctic (Malenfant et al, 2016; Paetkau et al, 1999)

Objectives

Findings

Discussion

Conclusion