No abstract

Coherent ecological networks (EN) composed of core areas linked by ecological corridors are being developed worldwide with the goal of promoting landscape connectivity and biodiversity conservation. However, empirical assessment of the performance of EN designs is critical to evaluate the utility of these networks to mitigate effects of habitat loss and fragmentation. Landscape genetics provides a particularly valuable framework to address the question of functional connectivity by providing a direct means to investigate the effects of landscape structure on gene flow. The goals of this study are (1) to evaluate the landscape features that drive gene flow of an EN target species (European pine marten), and (2) evaluate the optimality of a regional EN design in providing connectivity for this species within the Basque Country (North Spain). Using partial Mantel tests in a reciprocal causal modeling framework we competed 59 alternative models, including isolation by distance and the regional EN. Our analysis indicated that the regional EN was among the most supported resistance models for the pine marten, but was not the best supported model. Gene flow of pine marten in northern Spain is facilitated by natural vegetation, and is resisted by anthropogenic landcover types and roads. Our results suggest that the regional EN design being implemented in the Basque Country will effectively facilitate gene flow of forest dwelling species at regional scale.

Landscape genetics provides a valuable framework to understand how landscape features influence gene flow and to disentangle the factors that lead to discrete and/or clinal population structure. Here, we attempt to differentiate between these processes in a forest-dwelling small carnivore [European pine marten (Martes martes)]. Specifically, we used complementary analytical approaches to quantify the spatially explicit genetic structure and diversity and analyse patterns of gene flow for 140 individuals genotyped at 15 microsatellite loci. We first used spatially explicit and nonspatial Bayesian clustering algorithms to partition the sample into discrete clusters and evaluate hypotheses of 'isolation by barriers' (IBB). We further characterized the relationships between genetic distance and geographical ('isolation by distance', IBD) and ecological distances ('isolation by resistance', IBR) obtained from optimized landscape models. Using a reciprocal causal modelling approach, we competed the IBD, IBR and IBB hypotheses with each other to unravel factors driving population genetic structure. Additionally, we further assessed spatially explicit indices of genetic diversity using sGD across potentially overlapping genetic neighbourhoods that matched the inferred population structure. Our results revealed a complex spatial genetic cline that appears to be driven jointly by IBD and partial barriers to gene flow (IBB) associated with poor habitat and interspecific competition. Habitat loss and fragmentation, in synergy with past overharvesting and possible interspecific competition with sympatric stone marten (Martes foina), are likely the main factors responsible for the spatial genetic structure we observed. These results emphasize the need for a more thorough evaluation of discrete and clinal hypotheses governing gene flow in landscape genetic studies, and the potential influence of different limiting factors affecting genetic structure at different spatial scales.

Restriction site-associated DNA sequencing (RADseq) was used to jointly assess phylogenetic relationships, interspecific hybridization and species delimitation in the cryptic, non-model land snail complex Pyramidula. A robust phylogeny was inferred using a matrix of concatenated sequences of almost 1,500,000bp long, containing >97,000 polymorphic sites. Maximum likelihood analyses fully resolved the phylogenetic relationships among species and drastically improved phylogenetic trees obtained from mtDNA and nDNA gene trees (COI, 16S rRNA, 5.8S rRNA, ITS2 and 28S rRNA sequence data). The best species delimitation scenario was selected on the basis of 875 unlinked single nucleotide polymorphisms, showing that nine Pyramidula species should be distinguished in Europe. Applying D-statistics provided no or weak evidence of interspecific hybridization among Pyramidula, except for some evidence of gene flow between two species.

The role of southern European peninsulas as glacial refugia for temperate species has been widely established, but the role of cryptic northern refugia has only recently been addressed. Here, we describe the phylogeographic pattern of the forest‐dwelling European pine marten (Martes martes), using a 1600‐bp mitochondrial DNA (mtDNA) fragment from 287 individuals sampled across the entire distribution range of the species. To clarify the relationships between M. martes and its sister species the sable (Martes zibellina) in Fennoscandia and Russia, ten M. zibellina samples were also included in the analyses. Our results reveal the presence of 69 different haplotypes for M. martes and ten haplotypes for M. zibellina, which are split into three major assemblages: Mediterranean, central–northern European, and Fennoscandian–Russian clades, showing a global pattern of spatial segregation, with some area of overlap and genetic admixture. It is apparent that the Mediterranean phylogroup did not significantly contribute to the postglacial recolonization of most of the Palaearctic range of the species. Instead, most of Europe was colonized by the central–northern European phylogroup, which probably survived the last glaciations in northern cryptic refugia, as has previously been suggested by palaeontological studies. A highly divergent phylogroup has been discovered in Fennoscandia–Russia, which includes specimens from both Martes species. Calculations of divergence times suggest that the phylogroups split during the Pleistocene. Overall, our study indicates a complex phylogeographic history for M. martes, indicating a mixed pattern of recolonization of northern Europe from both Mediterranean and non‐Mediterranean refugia, providing new insights into the existence of cryptic northern glacial refugia for temperate species in Europe. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109, 1–18.