Analysing the recolonisation of a highly fragmented landscape by wild boar using a landscape genetic approach

Anneleen Rutten,Bram Vanden Broecke,Herwig Leirs,Karen Cox,Thomas Scheppers,Jim Casaer

doi:10.2981/wlb.00542

Abstract

Wild boar are currently one of the most widespread mammals of the world and in many regions populations keep expanding. In Flanders (Belgium), the wild boar has returned since 2006 after almost half a century of absence and numbers are increasing fast. The Flemish landscape is severely fragmented and is one of the most densely populated areas in the world. Understanding the relationship between landscape structures and species biology is the basis of landscape ecology and increases the understanding of factors driving habitat use, recolonisation and expansion. We conducted a landscape genetics study to identify factors driving wild boar expansion in Flanders. A total of 838 DNA-samples collected from the wild boar hunting bag between 2007 and 2016 were genotyped for 140 single nucleotide polymorphisms (SNPs). We show that the wild boar population expansion started from two local gene pools while staying relatively genetically distinct, though with some admixture. A third gene pool emerged around 2013 in the northwest coming from the Netherlands and Germany. The landscape genetic analysis revealed that the main factors explaining the spatial genetic pattern are isolation by distance and forest cover which influenced gene flow positively. Forest fragmentation had no significant effect on genetic distances. As human–wildlife conflicts are increasing in line with wild boars' expanding distribution range, understanding factors driving expansion during recolonisation is essential for assessing the future dispersal of wild boar in Flanders. With a better insight in future dispersal, it will be possible to conduct risk assessments which target more efficient management actions to limit human–wildlife conflicts.

Highlights

The relationship between landscape structures and the biology of a species forms the basis of landscape ecology (Coulon et al 2006)
Structure and landscape genetic analysis were run with the total set of 140 single nucleotide polymorphisms (SNPs) and were compared with the reduced set of 128 SNPs
Deviations from linkage disequilibrium (LD) and Hardy–Weinberg equilibrium (HWE) were found to have a substantial impact on population structure analysis as outcomes differed between both SNP sets

Summary

Introduction

The relationship between landscape structures and the biology of a species forms the basis of landscape ecology (Coulon et al 2006). Since the 1960s wild boar populations have been expanding throughout Europe (Saez-Royuela and Telleria 1986, Acevedo et al 2007, Massei et al 2015) and much of their invasive distribution range (New Zealand: Bengsen et al 2018; Australia: Choquenot et al 1996; North America: Mayer 2018, McClure et al 2015; South America: Salvador and Fernandez 2018). There is no official information on where these population originated from and these populations were geographically not connected to neighbouring populations Despite this highly fragmented landscape, wild boar numbers in Flanders are increasing rapidly (Scheppers et al 2014). The anthropogenic landscape causes frequent contacts between wild boar and human activities resulting in wildlife–human impacts and emerging human–wildlife conflicts (Young et al 2010)

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