Shall the Wild Boar Pass? A Genetically Assessed Ecological Corridor in the Geneva Region

Abstract

Landscape fragmentation caused by road infrastructures represents a major threat to the genetic diversity of a region. The resulting genetic isolation between subpopulations may lead to consanguinity, and consequently to population collapse and extinction. However, the construction of wildlife crossings can help maintain connectivity. In the present paper, we evaluated the genetic spatial structuring of populations of wild boars (Sus scrofa) in three areas of the Geneva region connected by an ecological corridor. Those areas are cut off either by a highway that is crossed by a wildlife overpass or by an anthropized sector. Genetic profiling with 9 nuclear microsatellite markers yielded 61 single profiles, which allowed for clustering, parentage, and linkage disequilibrium analyses, uncovering the populations’ genetic structure. We also evaluated whether the genetic structure was affected by the sex of individuals. In our analyses, all individuals clustered into a single genetic group, suggesting that no structure limited significantly the gene flow in the region. However, a recent admixture indicated a potential increase in the gene flow between two of the subpopulations due to the wildlife overpass, while the other part of the ecological corridor was not or was only partially functional. Genetic distances between males were significantly higher than between females, although the role of sex remains unclear as to its influence on population genetics. Finally, in order to avoid a subregion becoming fully isolated, urbanization planning should consider this genetic evaluation and proceed with further monitoring, especially by focusing on species more sensitive to landscape fragmentation.

Changes in the Genetic Structure of Lithuania’s Wild Boar (Sus scrofa) Population Following the Outbreak of African Swine Fever

“…However, the observed heterozygosity value (Ho = 0.623) was close to that quantified in the earlier study on wild boars (Ho = 0.627), despite the fact that the sample size in the current study was four times greater. Similar levels of Ho have also been detected in Bulgaria [ 18 ], Portugal [ 19 ], Croatia [ 39 ] and the Geneva region [ 25 ].…”

“…In contrast, one genetic cluster was confirmed in the Lithuanian wild boar population before ASF [ 24 ] and two genetic groups were identified in wild boar populations in the Carpathian Basin [ 23 ]. The homogenous genetic structure was also confirmed in a recent study that showed the clustering of all individuals into a single genetic group in three areas of the Geneva region connected by an ecological corridor [ 25 ]. The contrasting findings in the present study compared with previous studies may be related to the geographic scale of the study, the use of different markers and the sample size.…”

“…To limit the spread of ASF, control measures such as sanitary culling induced mortality that could contribute to the wild boar population decline [ 11 ]. Many research studies have focused on genetic analysis to understand the phylogeographic [ 12 , 13 , 14 , 15 , 16 ] and population genetic structure of the European wild boar [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ]. Although various studies of the wild boar’s genetic structure have been conducted, most of them have focused on the demographic history and investigations of the natural and artificial barriers.…”