A NEW PhD IN THE TEAM
Posted by Enrique Macpherson
On February, the 3rd, our team member Héctor Torrado defended his PhD “From genomics to models: Population studies at individual level in littoral fishes from the Western Mediterranean”. He was supervised by Marta Pascual and Enrique Macpherson.
Dr. Torrado obtained the congratulations and highest marks from the jury. We join these congratulations and celebrate having a new doctor in the group.
This is the abstract of his dissertation:
Connectivity and local adaptation are two contrasting evolutionary forces influencing population structure. Due to their complex life cycle, marine fish species tend to be structured in metapopulations, connected almost exclusively by movements in the larval phase. In this thesis, we study the population genomic structure of several Mediterranean littoral fishes and the potential factors affecting their distribution. To asses this goal, we combine a set of different methodologies including population genomics, otolith reading, oceanographical dispersion models and graph theory.
We show a negative effect of temperature on pelagic larval duration but no effect on settlement size and thus raising temperatures would reduce dispersal capabilities of fishes. With an individual-based oceanographic dispersal model, we observed an effect of both hatching date and pelagic larval duration in the dispersal distances and orientations, but variable among species. Furthermore, we found a clear effect of the oceanographic fronts in dispersal capabilities of our species, allowing us to identify three hydrodynamic units in the Western Mediterranean delimited by these fronts.
We found different genomic structuring between sympatric species of Symphodus despite their similar early life traits. Nonetheless, we identified in both species candidate regions for local adaptation by combining outlier analysis with environmental and phenotypic association analyses. We provided tools and guidelines for laboratory and bioinformatics analyses to optimise studies using 2b-RAD sequencing on different non-model organisms with different genome sizes. Additionally, we found in three different localities clear trends of selective mortality for hatch date and lower for growth rate and pelagic larval duration in a common littoral fish. We confirmed these results with a phenotype-genotype association study, finding loci related with these traits, suggesting a genetic basis of differential mortality between settlers and survivors. Finally, we defined the main clusters and the main nodes of connectivity in three fish species in the Western Mediterranean. With this information, we evaluated the protection state of the areas with high importance for connectivity maintenance, finding a small proportion of them protected. All together, these results provide new valuable information about connectivity, population structure and adaptation in littoral fishes of the Mediterranean Sea.
Congratulations, Héctor!