Restricted dispersal and inbreeding in a high-elevation birdacross the ‘sky islands’ of the European Alps

Ceresa F., M. Brambilla, L. Kvist, S. Vitulano, M. Pes, L. Tomasi, P. Pedrini, C. Bettega, M. Anderle, A. Hilpold, P. Kranebitter.

2024

Journal of Biogeography

51

Aim: High-elevation specialist species are threatened by climate change and habitatloss, and their distributions are becoming increasingly reduced and fragmented. In sucha context, dispersal ability is crucial to maintain gene flow among patches of suitablehabitat. However, information about dispersal is often lacking for these species, espe-cially for those taxa that are usually considered as good dispersers such as birds. Weadopted a landscape genomics approach to investigate dispersal in a climate-sensitivehigh-elevation specialist bird. Our aims were to assess the levels of gene flow within awide mountain area, and to assess the effects of geographic distance and landscapecharacteristics on dispersal, by testing the isolation by distance (IBD) hypothesis againstthe isolation by resistance (IBR) hypothesis.
Location: European Alps.
Taxon: Montifringilla nivalis.
Methods: We sampled individuals from several breeding areas and obtained single nu-cleotide polymorphism (SNP) data by ddRAD sequencing. We then calculated site- andindividual level genetic distances and individual inbreeding coefficients. To test IBD ver-sus IBR, we related genetic distances to both geographic distances and different meas-ures of landscape resistance by using maximum likelihood population effects models.Results: Gene flow among breeding areas was partly restricted, and we found sup-port for IBD, indicating that geographic distance limits snowfinch dispersal. Spatialpatterns of genetic distances suggested that philopatry strongly contributed to deter-mine the observed IBD. High inbreeding coefficients in several individuals indicatedfrequent mating among relatives.
Main Conclusions: Restricted dispersal and frequent inbreeding within ‘sky island’systems can also occur in highly mobile species, because their potential ability tocover very large distances can be counteracted by high philopatry levels that are likelyrelated to high dispersal costs. IBD and philopatry will increasingly hinder snowfinchdispersal among suitable areas within the future more restricted and fragmentedbreeding range, increasing the risks of local extinctions.

High-mountain conservation; Isolation by distance; Isolation by resistance; Maximum likelihoodpopulation effects (MLPE) models; Montifringilla nivalis; White-winged snowfinch