Francesca Raffini, postdoctoral researcher at the Molecular Ecology Laboratory (University of Sheffield), led a new session of the Café con Sal lecture series, a meeting point between researchers, students and professionals from the marine sector promoted by the Marine Research Centre in order to share knowledge, generate debates and new ideas. In this penultimate event of the 2018-2019 academic year, Raffini delved into the different evolutionary forces responsible for the adaptive polymorphism of the wild snail Littorina saxatilis, exemplifying the factors and interactions that favor the speciation process in the presence of gene flow in natural populations. During her lecture, Francesca Raffini presented the preliminary results on the “phenotypic and genomic variation along the transects studied in the hybrid zone of L. saxatilis in Galicia”.
Littorina saxatilis, an example of adaptive divergence
The process of speciation, explained the researcher, requires the evolution of barriers to gene flow between diverging populations, but the mechanisms underlying these processes are largely unknown, particularly in the case of divergence in the presence of gene flow. According to Raffini, a very suitable study model for understanding the factors involved in adaptive divergence with gene flow is the snail L. saxatilis. “This intertidal species has an ecotype adapted to strong waves and another adapted to predation by crabs, and both are found repeatedly along the coast as a result of an adaptive divergence. These ecotypes present an ecological, morphological and behavioral divergence, but nevertheless they are found hybridizing in the mid-intertidal zone where crab predation and wave exposure overlap.”
Research at Ecimat
To advance our understanding of this speciation process, Raffini, in collaboration with Professor Roger Butlin of the University of Sheffield, a group of researchers from CIM-UVigo including Emilio Rolán and Juan Galindo, as well as scientists from the universities of Gothenburg and Sheffield, are carrying out ecological field studies combined with genomic analysis (low coverage whole genome resequencing) of samples from the hybrid zone of L. saxatilis. Their main objective is to determine the genomic architecture of the local adaptation of these ecotypes and the speciation in the presence of gene flow that is happening in parallel on the coasts of Sweden and Galicia. “The results achieved will improve our knowledge of the role of environmental and genetic mechanisms in the speciation process, such as different types of selective forces, associative mating, habitat choice or genomic architecture.”
The studies carried out at Ecimat are part of the project Insights from hybrid zones: testing for habitat choice, divergent selection and genomic architecture in Littorina saxatilis adaptive divergence, funded by Assemble Plus.
