title: Small-scale patterns in snowmelt timing affect gene flow and the distribution of genetic diversity in the alpine dwarf shrub Salix herbacea.
abstract: Current threats to biodiversity, such as climate change, are thought to alter the within-species genetic diversity among microhabitats in highly heterogeneous alpine environments. Assessing the spatial organization and dynamics of genetic diversity within species can help to predict the responses of organisms to environmental change. In this study, we evaluated whether small-scale heterogeneity in snowmelt timing restricts gene flow between microhabitats in the common long-lived dwarf shrub Salix herbacea L. We surveyed 273 genets across 12 early- and late-snowmelt sites (that is, ridges and snowbeds) in the Swiss Alps for phenological variation over 2 years and for genetic variation using seven SSR markers. Phenological differentiation triggered by differences in snowmelt timing did not correlate with genetic differentiation between microhabitats. On the contrary, extensive gene flow appeared to occur between microhabitats and slightly less extensively among adjacent mountains. However, ridges exhibited significantly lower levels of genetic diversity than snowbeds, and patterns of effective population size (Ne) and migration (Nem) between microhabitats were strongly asymmetric, with ridges acting as sources and snowbeds as sinks. As no recent genetic bottlenecks were detected in the studied sites, this asymmetry is likely to reflect current meta-population dynamics of the species dominated by gene flow via seeds rather than ancient re-colonization after the last glacial period. Overall, our results suggest that seed dispersal prevents snowmelt-driven genetic isolation, and snowbeds act as sinks of genetic diversity. We discuss the consequences of such small-scale variation in gene flow and diversity levels for population responses to climate change.
authors.affiliation: Unit of Plant Ecology and Evolution, Evolutionary Biology Center, Department of Ecology and Genetics, Uppsala University, Uppsala, Sweden.
authors.forename: A J
authors.initials: AJ
authors.lastname: Cortés
authors.affiliation: Unit of Ecology and Evolution, Department of Biology, University of Fribourg, Fribourg, Switzerland.
authors.forename: S
authors.initials: S
authors.lastname: Waeber
authors.affiliation: Unit of Ecology and Evolution, Department of Biology, University of Fribourg, Fribourg, Switzerland.
authors.forename: C
authors.initials: C
authors.lastname: Lexer
authors.affiliation: Ecology, Department of Biology, University of Konstanz, Konstanz, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Sedlacek
authors.affiliation: 1] WSL Institute for Snow and Avalanche Research SLF, Davos, Switzerland [2] Institute of Botany, University of Basel, Basel, Switzerland.
authors.forename: J A
authors.initials: JA
authors.lastname: Wheeler
authors.affiliation: Ecology, Department of Biology, University of Konstanz, Konstanz, Germany.
authors.forename: M
authors.initials: M
authors.lastname: van Kleunen
authors.affiliation: Plant Evolutionary Ecology, University of Tübingen, Tübingen, Germany.
authors.forename: O
authors.initials: O
authors.lastname: Bossdorf
authors.affiliation: Institute of Botany, University of Basel, Basel, Switzerland.
authors.forename: G
authors.initials: G
authors.lastname: Hoch
authors.affiliation: WSL Institute for Snow and Avalanche Research SLF, Davos, Switzerland.
authors.forename: C
authors.initials: C
authors.lastname: Rixen
authors.affiliation: WSL Institute for Snow and Avalanche Research SLF, Davos, Switzerland.
authors.forename: S
authors.initials: S
authors.lastname: Wipf
authors.affiliation: Unit of Plant Ecology and Evolution, Evolutionary Biology Center, Department of Ecology and Genetics, Uppsala University, Uppsala, Sweden.
authors.forename: S
authors.initials: S
authors.lastname: Karrenberg
mesh_terms: D057231:Climate Change; D017753:Ecosystem; D035264:Flowers / Q000235:genetics; D051456:Gene Flow / Q000235:genetics*; D014644:Genetic Variation / Q000235:genetics*; D011156:Population Density; D011157:Population Dynamics; D032108:Salix / Q000235:genetics*; D012621:Seasons; D012639:Seeds / Q000235:genetics