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Aim: Ecological marginality is the existence of species/populations in the margins of their ecological niche, where conditions are harsher, and the risk of extinction is more pronounced. In threatened long-lived species, the disparity between distribution and population demography may provide understanding of how environmental heterogeneity shapes ecological marginality, potential extinction patterns and range shifts. We set out to evaluate this by combining a species distribution model (SDM) with population-specific demography data. Location: Sweden, 450,000?km2. Major Taxa Studied: Freshwater pearl mussel (FPM, Margaritifera margaritifera) and two salmonid fish species. Methods: A SDM for the mussel was constructed with MaxEnt using salmonid host fish (Salmo trutta plus S. salar) density, extreme low and high temperatures, precipitation, altitude, and clay content as explanatory variables. The output was used to test the ecological marginality hypothesis by evaluating whether lowly predicted populations had higher loss of recruitment. Logistic regression was used to explicitly test the factors involved in recruitment loss. Results: Host fish density contributed the most (50.3%) to the mussel distribution, followed by lowest temperature the coldest month (34.3%) and altitude (10.3%), while the remaining explanatory variables contributed minimally ( |
