Strong genetic differentiation but not local adaptation toward the range limit of a coastal dune plant |
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| Authors: | Karen E Samis Adriana López‐Villalobos Christopher G Eckert |
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| Affiliation: | 1. Department of Biology, Queen's University, Kingston, Ontario, Canada;2. Current Address: Department of Biology, University of Prince Edward Island, Charlottetown, Prince Edward Island, Canada |
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| Abstract: | All species have limited geographic distributions; but the ecological and evolutionary mechanisms causing range limits are largely unknown. That many species’ geographic range limits are coincident with niche limits suggests limited evolutionary potential of marginal populations to adapt to conditions experienced beyond the range. We provide a test of range limit theory by combining population genetic analysis of microsatellite polymorphisms with a transplant experiment within, at the edge of, and 60 km beyond the northern range of a coastal dune plant. Contrary to expectations, lifetime fitness increased toward the range limit with highest fitness achieved by most populations at and beyond the range edge. Genetic differentiation among populations was strong, with very low, nondirectional gene flow suggesting range limitation via constraints to dispersal. In contrast, however, local adaptation was negligible, and a distance‐dependent decline in fitness only occurred for those populations furthest from home when planted beyond the range limit. These results challenge a commonly held assumption that stable range limits match niche limits, but also raise questions about the unique value of peripheral populations in expanding species’ geographical ranges. |
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| Keywords: | Geographic range local adaptation Onagraceae peripheral populations population genetic structure reciprocal transplant experiment |
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