Using isolation-by-distance-based approaches to assess the barrier effect of linear landscape elements on badger (Meles meles) dispersal

Abstract

As the European badger (Meles meles) can be of conservation or management concern, it is important to have a good understanding of the species' dispersal ability. In particular, knowledge of landscape elements that affect dispersal can contribute to devising effective management strategies. However, the standard approach of using Bayesian clustering methods to correlate genetic discontinuities with landscape elements cannot easily be applied to this problem, as badger populations are often characterized by a strong confounding isolation-by-distance (IBD) pattern. We therefore developed a two-step method that compares the location of pairs of related badgers relative to a putative barrier and utilizes the expected spatial genetic structure characterized by IBD as a null model to test for the presence of a barrier. If a linear feature disrupts dispersal, the IBD pattern characterising pairs of individuals located on different sides of a putative barrier should differ significantly from the pattern obtained with pairs of individuals located on the same side. We used our new approach to assess the impact of rivers and roads of different sizes on badger dispersal in western England. We show that a large, wide river represented a barrier to badger dispersal and found evidence that a motorway may also restrict badger movement. Conversely, we did not find any evidence for small rivers and roads interfering with badger movement. One of the advantages of our approach is that potentially it can detect features that disrupt gene flow locally, without necessarily creating distinct identifiable genetic units.

Genetic structure of a Virginia opossum (Didelphis virginiana) population inhabiting a fragmented agricultural ecosystem

“…Also, analyses did not reveal any significant barriers to gene flow despite the presence of three rivers and two large reservoirs within the study area. Although rivers have been shown to be significant barriers to dispersal in both European badgers (Meles meles (L., 1758)) and raccoons (Cullingham et al 2009;Frantz et al 2010), Virginia opossums are effective swimmers (McManus 1974) and are known to readily use anthropogenic features (e.g., bridges) to traverse both rivers and reservoirs. In addition, the unique taxonomic and natural history characteristics of the Virginia opossum likely contribute to the absence of genetic structure at the landscape scale.…”

Phylogeny, molecular ecology and taxonomy of southern Iberian lineages of Triops mauritanicus (Crustacea: Notostraca)

“…The possible effect of rivers as barriers to successful dispersal would imply that mammals were an important dispersal vector, since they might avoid crossing large rivers (e.g. Eriksson et al 2004;Frantz et al 2010) or might lose a high proportion of adherent mud with resting stages from temporary ponds (Thiéry 1987;Vanschoenwinkel et al 2008) due to wash off (or abrasion of macerated mud by river sediments or riverine vegetation). This appears to be in conflict with our interpretation that mammals were less effective dispersal vectors within the Guadalquivir delta (see above).…”

Fine-scale landscape genetics of the American badger (Taxidea taxus): disentangling landscape effects and sampling artifacts in a poorly understood species

“…American badger's tolerance for fragmentation and overall high gene flow differs greatly from the more well-studied European badger (Meles meles) populations in the United Kingdom and Ireland. In European badgers, multiple authors have recorded evidence for restricted dispersal owing to both natural (that is, rivers; Sleeman et al, 2009;Frantz et al, 2010b) and anthropogenic (roads; Clark et al, 1998;Frantz et al, 2010a) barriers, as well as strong fine-scale IBD created by philopatry within dense populations (Pope et al, 2006;Frantz et al, 2010a). American badgers, in contrast, do not avoid large roads (Apps et al, 2002), do not form social groups and occur at lower densities than UK badger populations, so the difference in gene flow patterns likely stems from their disparate ecologies.…”