The application of phylogeographic analysis toward the conservation of marine biodiversity of Macaronesian and Cape Verd islands

Abstract

The long-term conservation of marine biodiversity is still a challenge issue because elucidate the complexity of biological mechanisms, ecological interactions and evolutionary processes underlying the hierarchy of biodiversity are mostly hard to obtain. However, population genetic studies can efficiently incorporate the knowledge of evolutionary processes and the distribution of genetic diversity into a conservation planning. Hence, priority setting for populations within species with: (i) high levels of genetic diversity and (ii) the delineation of Evolutionary Significant Units as historically isolated lineages (sensu Moritz 2002) can be useful information to efficiently preserve both relevant attributes and keystone processes that create and sustain biodiversity. In the marine realm, oceanic archipelagos are spots which facilitate stepping stone colonization events towards new distant habitats across the oceans expanding the geographic distribution of marine species and/or maintaining genetic connectivity across the landscape. In contrast, marine species living in oceanic archipelagos might not interchange gametes, larvae or adults among other archipelagos and/or mainland, reaching reproductive isolation. Hence, the contribution of oceanic archipelagos to the evolution of marine biota in the central Eastern Atlantic Ocean has been decisive. In this sense, inferences on the levels of genetic diversity and the spatial scale for which gene flow maintains genetic connectivity among oceanic islands across the Eastern Atlantic ocean applied to preserve island marine biodiversity is still scarce. Thus, the aim of the present study try to understand the genetic structure and the levels of genetic connectivity among the Azores, Madeira, Canary and Cape Verde archipelagos located in the Eastern Atlantic using several benthic and demersal marine species. Those species included the common octopus Octopus vulgaris, the Azorean barnacle Megabalanus azoricus, the parrotfish Sparisoma cretense, the grapsid Grapsus adscensionis and the soldier striped shrimp Plesionika edwardsii. A total of 50 specimens per archipelago were sampled. After DNA extraction using up to 30 mg of tissue and following the E.Z.N.A. Tissue mollusk kit (Omega Bio-Tek) protocol, the mitochondrial hypervariable non-codifying control region was amplified using both specific primers designed for this study and PCR conditions for each species. After chromatogram revision, the nucleotide sequences were aligned and then nucleotide and haplotype diversity, FST, AMOVA, phylogenetic Neighbour-Joining Tree and haplotype Median Joining Network were performed to resolve the questions and hypothesis related to each analysis. The combination of all above analyses showed a phylogeographic pattern for M. azoricus, G. adscensionis and O. vulgaris in which the haplotypes of Cape verde population reached the highest levels of significant genetic differentiation. This fact clearly manifest that the Macaronesian archipelagos (Azores, Madeira and Canary Islands) have maintained higher levels of genetic connectivity among them, favoured by the oceanic currents of the subtropical gyre in the central northeastern Atlantic. In contrast, S. cretense and P. edwardsii showed a panmitic population in the whole area, including the capeverdian population for which no significant genetic differentiation was detected. Hence, a mixed effect produced by both the canary current that continuously drive larval dispersal southward and the evolutionary history of the species during the quaternary glaciations could explain the evolutionary history among all archipelagos. Thus, the current geographic distribution of divergent majoritarian haplogroups and genetic diversity estimates among species and archipelagos were mainly explained by life cycle, habitat availability, demography and dispersal capacity as well as the oceanographic dynamics in the area. Keeping in mind the main objective regard to conservation genetics should be the maintenance of evolutionary processes and the viability of species and functional landscapes necessary to achieve this. Thus, the above phylogeographic analyses will allow using genetic diversity to highlight discrete genetic units (Evolutionary Significant Units or Conservation Units) as historically isolated lineages considering the landscape across the macaronesian and Cape Verde islands.