Topshell populations in the Cantabrian coast: Connectivity and adaptation to local niches

The main role for genetics in marine invertebrates is the identification of species and groups of interbreeding individuals. The mobility of both larvae and adult in shellfish indicates that dispersal, and hence population structuring, is likely to be different between species. Isolated populations of species with low dispersal capacity are far more vulnerable to overfishing/environmental changes than populations with more connectivity. An additional difficulty for understanding population structuring and designing sustainable management plans in shellfish is phenotypic plasticity, which may cause misidentification of morphologically similar species. Genetic studies to date indicate a remarkably high incidence of cryptic speciation in marine invertebrates, sometimes even in well studied commercially important species (Thorpe et al., 2000). The North Iberian topshells that inhabit intertidal levels belong principally to the genera Gibbula and Osilinus. Throughout their distribution area in the North Atlantic and Mediterranean Sea, they have been model species for investigating the effects of climate change on marine communities because they exhibit differential sensitivity to temperature shifts (e.g. Hawkins et al. 2009). The Iberian coast is not an exception. Range shifts in gastropods and therefore changes in intertidal communities have been reported for the Iberian Peninsula associated with sea surface temperature (Rubal et al. 2013). In some areas there are spatial temperature shifts due to the influence of currents and abrupt physical barriers in the shore landscape, such as in the North Iberian Cantabric Sea. The east of the coast is warmer than the west due to different influence of warmer currents in the eastern Bay of Biscay, and this promotes life-history and composition differences in some species assemblages like limpets at the two sides of the northernmost point of the Iberian coast, the Cape Peñas (Muñoz-Colmenero et al. 2012). However, the topshell community of the North Iberian coast, which is the most studied model in Europe, has never been studied in this zone. In this study the candidate will sample topshells from the west and east of the Cape Peñas in a geographical range of at least 100 km. He will measure them, and from minimal tissue biopsy extract DNA, PCR-amplify mitochondrial/nuclear sequences for determining the species first, then calculating gene flow between contiguous sampling sites to inferring connectivity of the existing populations. Signals of local adaptation to temperature will be identified combining morphological, genetic and demographic data. In fact, little is known about the patterns of genetic connectivity among populations for gastropod species in the Cantabric littoral, and about how human and environmental factors reshaped these patterns. This work will help to assess this for this environmentally relevant geographical area.

ISCED Categories

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0511 - Biology", "0521 - Ecology