title: Isolation by distance, resistance and/or clusters? Lessons learned from a forest-dwelling carnivore inhabiting a heterogeneous landscape.
abstract: 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.
authors.affiliation: Department of Zoology and Animal Cell Biology, University of the Basque Country, UPV/EHU, C/Paseo de la Universidad 7, 01006, Vitoria-Gasteiz, Spain.|Systematics, Biogeography and Population Dynamics Research Group, Lascaray Research Center, University of the Basque Country, UPV/EHU, Avda. Miguel de Unamuno, 3, 01006, Vitoria-Gasteiz, Spain.|Conservation Genetics Laboratory, National Institute for Environmental Protection and Research, ISPRA, Via Cà Fornacetta 9, 40064, Ozzano dell'Emilia, Bologna, Italy.
authors.forename: Aritz
authors.initials: A
authors.lastname: Ruiz-Gonzalez
authors.affiliation: U.S. Forest Service, Rocky Mountain Research Station, 2500 S. Pine Knoll Dr., 86001, Flagstaff, AZ, USA.
authors.forename: Samuel A
authors.initials: SA
authors.lastname: Cushman
authors.affiliation: Department of Zoology and Animal Cell Biology, University of the Basque Country, UPV/EHU, C/Paseo de la Universidad 7, 01006, Vitoria-Gasteiz, Spain.|Systematics, Biogeography and Population Dynamics Research Group, Lascaray Research Center, University of the Basque Country, UPV/EHU, Avda. Miguel de Unamuno, 3, 01006, Vitoria-Gasteiz, Spain.
authors.forename: María José
authors.initials: MJ
authors.lastname: Madeira
authors.affiliation: Conservation Genetics Laboratory, National Institute for Environmental Protection and Research, ISPRA, Via Cà Fornacetta 9, 40064, Ozzano dell'Emilia, Bologna, Italy.|Department 18/Section of Environmental Engineering, Aalborg University, Sohngårdsholmsvej 57, 9000, Aalborg, Denmark.
authors.forename: Ettore
authors.initials: E
authors.lastname: Randi
authors.affiliation: Department of Zoology and Animal Cell Biology, University of the Basque Country, UPV/EHU, C/Paseo de la Universidad 7, 01006, Vitoria-Gasteiz, Spain.|Systematics, Biogeography and Population Dynamics Research Group, Lascaray Research Center, University of the Basque Country, UPV/EHU, Avda. Miguel de Unamuno, 3, 01006, Vitoria-Gasteiz, Spain.
authors.forename: Benjamín J
authors.initials: BJ
authors.lastname: Gómez-Moliner
mesh_terms: D000818:Animals; D001499:Bayes Theorem; D016000:Cluster Analysis; D004272:DNA, Mitochondrial / Q000235:genetics; D065928:Forests; D051456:Gene Flow; D014644:Genetic Variation; D005828:Genetics, Population; D005838:Genotype; D018895:Microsatellite Repeats; D008957:Models, Genetic; D045969:Mustelidae / Q000235:genetics*; D017422:Sequence Analysis, DNA; D013030:Spain
chemical_list: D004272:DNA, Mitochondrial
keywords: Bayesian analysis; Martes martes; isolation by cluster; isolation by distance; isolation by landscape resistance; landscape genetics; reciprocal causal modelling