Recent large-scale landscape changes, genetic drift and reintroductions characterize the genetic structure of Norwegian wild reindeer

Kjersti S. Kvie,Knut H. Røed,Bård-Jørgen Bårdsen,Jan Heggenes

doi:10.1007/s10592-019-01225-w

Abstract

Landscape changes, such as habitat loss and fragmentation, subdivide wild populations, reduce their size, and limit gene flow. These changes may further lead to depletion of genetic variation within populations as well as accelerating differentiation among populations. As a migratory species requiring large living areas, wild reindeer (Rangifer tarandus) is highly vulnerable to human activity. The number and continued presence of wild reindeer have been significantly reduced due to accelerating anthropogenic habitat modifications, as well as displacement in benefit of domesticated herds of the species. As a basis for future management strategies we assess genetic structure and levels of genetic variation in Norwegian wild reindeer by analysing 12 microsatellite loci and the mitochondrial control region in 21 management units with varying population sizes. Overall, both markers showed highly varying levels of genetic variation, with reduced variation in the smaller and more isolated populations. The microsatellite data indicated a relationship between population size and genetic variation. This relationship was positive and linear until a threshold for population size was reached at approximately 1500 reindeer. We found high levels of differentiation among most populations, indicating low levels of gene flow, but only a weak correlation between geographic and genetic distances. Our results imply that the genetic structure of Norwegian wild reindeer is mainly driven by recent colonization history, population size, as well as human-induced landscape fragmentation, restricting gene flow and leading to high levels of genetic drift. To sustain viable populations, conservation strategies should focus on genetic connectivity between populations.

Highlights

Large-scale landscape changes are intimately linked to habitat loss and fragmentation, and pose major threats to biodiversity where many populations are declining, and many species are currently at the brink of extinction (Frankham et al 2010; Barnosky et al 2011; Ripple et al 2017)
Assessing Hardy–Weinberg equilibrium (HWE) for 12 loci across 21 populations resulted in 252 statistical tests
As the majority of these tests were non-significant (> 96%), and as no locus or population were over-represented among these tests, we conclude that our data do not show any major deviation from HWE

Summary

Introduction

Large-scale landscape changes are intimately linked to habitat loss and fragmentation, and pose major threats to biodiversity where many populations are declining, and many species are currently at the brink of extinction (Frankham et al 2010; Barnosky et al 2011; Ripple et al 2017). Genetic erosion of small populations has become a major conservation concern, as low levels of variation is considered limiting to the ability for populations to respond to changed environmental conditions as well as threats like diseases, parasites and predators (Amos and Harwood 1998). Mitochondrial DNA (mtDNA) variation did not reflect population size, probably as an effect of selection acting on mtDNA. This conclusion was, based on comparisons of within-species variation among different taxa which probably differ in other aspects like geographic location, population history, mutation rates and population structure, all of which potentially affect genetic variation (Hague and Routman 2015)

Methods

Results

Conclusion