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The population structure of natural populations of Californian stickleback (Gasterosteus aculeatus) in dynamic estuaries
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Biology Education Centre. McGill University.
2015 (English)Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
Abstract [en]

There is still much to be understood regarding the role of natural selection in shaping adaptive divergence between wild populations, particularly regarding the relative roles that stochastic and selective mechanisms play in this process. An excellent example of adaptive divergence is the parallel evolution of the threespine stickleback (Gasterosteus aculeatus), where completely plated marine fish have repeatedly evolved towards armor reduction in freshwater environments. Interestingly, the phenotypic trajectories along which this species has adapted vary along its distribution range and polymorphisms in genes crucial for these adaptations still exist. By studying wild populations of threespine stickleback in dynamic estuaries along the coast of Santa Cruz, California, this study is an initial part of a project aiming to shed further light on the mechanisms of adaptive divergence. Questions to be answered here regard the population structure of these insofar unstudied populations. Seven putatively neutral and two microsatellite markers associated to genes known to facilitate freshwater adaptations were considered. Levels of diversification were estimated across and within populations, using estimates of Fst, FIS and heterozygosity. The level of neutral population structure was low and no evidence of geographic isolation was found. Estimates of selection acting on the population did not indicate strong divergent selection at two adaptive markers as compared to the neutral ones. This study concludes that the balance between selective and neutrally selective processes for adaptive divergence may be more complex than what has typically been described for wild stickleback populations.

Place, publisher, year, edition, pages
Keyword [en]
EDA, population structure, adaptive divergence, Gasterosteus aculeatus
National Category
URN: urn:nbn:se:uu:diva-263505OAI: oai:DiVA.org:uu-263505DiVA: diva2:858228
Educational program
Master Programme in Biology
Available from: 2016-06-30 Created: 2015-10-01 Last updated: 2016-06-30Bibliographically approved

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