Genetic structure and connectivity in coastal marine invertebrate species

Abstract

Biodiversity loss, and the conservation measures needed to mitigate it, requieres a deep understanding of the dynamics of its components at different temporal and spatial scales. Information on dispersal and connectivty processes between populations is key as key directly impact the adaptive potential of species and their persistence over time. Various abiotic factors can modulate connectivity and understanding these factors is crucial for recognizing population patterns and predicting their future behaviour in the face of natural and anthropogenic enviromental changes. In this thesis, a group of marine invertebrate species (two gastropod molluscs, Gibbula divaricata and Dendropoma lebeche, and one scleractiniam coral, Cladocora caespitosa) with coastline-restricted habitats was studied. Using hypervariable molecular markers, the genetic variation, population structure and connectivity of these species werw analysed in order to make inferences about their recent evolutionary history, and the processes and parmeters that have determined or conditioned it.

A novelty of this study lies in the different geographic scales (micro-, meso-, and large- scales) at which the selected species were studied. Such an approach has never been attempted with the selected species, and is rarely done with marine invertebrates endemic to the Mediterranean. An advantage of this approach is that it allowed comparisons amog the three studies species to be made, and the influence of certain life history traits on the differentiation patterns observed to be tested. Finally, the researh presented in this thesis is framed within the context of "seascape genetics", a rapidly advancing area of population genetics in which to better understand drivers of gene flow and potential barries to connectivity among popilations. The abiotic factors determining (or influencing) the observed differentiation patterns of the studied species were evaluated and discussed under this framework. Among the seascape variables considered, salinity emerged as a primary driver modulating gene flow for both gastropods in combination with sea surface temperature and currents. The coral connectivty resulted affected primarily by distance along the coastline by a stepping stone pathway and, secondarily, by sea surface currents.