Molecular phylogenesis of Mediterranean Octocorals

In order to support the conservation of the Mediterranean octocorals improvements on information regarding their taxonomic units and phylogenetic relationships are strongly needed. In the present thesis work, phylogenetic analyses based on the mitochondrial mtMSH and 16S genes were performed including 15 Mediterranean octocorals species on the 56 recognized to date. Moreover, an extended datasets with Atlanto/Pacific congeners Octocorallia species was implemented to clarify their phylogenetic relationships and estimate the divergence times of the Mediterranean species. Results indicated that: 1) there are similarity and differences among molecular and morphological traits depending on the taxonomical level considered; 2) the molecular phylogeny of the Mediterranean octocorals retrace the previous relationships based on wide octocorals analyses; and 3) the divergence time among Mediterranean and Atlanto/Pacific species varies depending on analysed taxa. At higher taxonomic level, the Mediterranean trees supported the division of the Mediterranean Octocorallia into one major clade (Alcyoniina-Holaxonia) plus two unresolved branch including the single species available of Scleraxonia and Stolonifera respectively. This topology was better supported including the Atlanto/Pacific congeners species. The molecular evidence suggested that Alcyonium palmatum and Corallium rubrum species are the youngest with a divergence time estimated around 4 MYA. Particularly, C. rubrum results were in agreement with the hypothesis that recent orogenesis process of the Mediterranean Sea promoted the allopatric speciation of this specie. Increasing the sample design and implementing the emerging next-generation genomic-sequencing technologies, further studies would be able to improve the understanding of the Mediterranean octocorals phylogenetic relationships and evolution.

Phylogeny and phylogeography of the family Hyalidae (Crustacea: Amphipoda) along the northeast Atlantic coasts

The family Hyalidae comprises more than one hundred species, distributed worldwide. They are common and abundant in the littoral and shallow sublittoral habitats and they play an important role in the coastal food chain. Most studies about this family were dealing with taxonomy and ecology, while very little is known about phylogenetic relationship among genera and species. In the present study we aim to achieve the first approach of the phylogenetic patterns of this family in NE Atlantic Ocean and Mediterranean Sea, and to perform the first insight into the phylogeography Apohyale prevostii along both the North Atlantic coasts. In order to do that, eight species belonging to the genera Apohyale, Hyale, Serejohyale and Protohyale were investigated using the mitochondrial COI-5P barcode region. Specimens were collected along European and Moroccan Atlantic rocky shores, including Iceland, the British Isles, Macaronesia and in the Mediterranean Sea. Sequences of A. prevostii, from the NW Atlantic Ocean, available in BOLD and GenBank, were retrieved. As expected, phylogenetic analyses showed highly-divergent clades, clearly discriminating among different species clusters, confirming their morphology-based identifications. Although, within A. perieri, A. media, A. stebbingi, P. (Protohyale) schmidtii and S. spinidactylus, high genetic diversity was found, revealing putative cryptic species. The clade of A. prevostii and A. stebbingi appears well supported and divided from the other two congeneric species, and P. (Protohyale) schmidtii shows a basal divergence. The north-western Atlantic coasts were recently colonized by A. prevostii after the last glacial maximum from the European populations showing also a common haplotype in every population analysed. The use of the COI-5P as DNA barcode provided a good tool to underline the necessity of a revision of this emblematic family, as well as to discern taxonomically the possible new species flagged with this molecular device.

Inference of Raja miraletus population structure using mitochondrial and nuclear DNA: comparing the resolution power of molecular markers in exploring species and population boundaries

This study focused on the role of oceanographic discontinuities and the presence of transitional areas in shaping the population structure and the phylogeography of the Raja miraletus species complex, coupled with the test of the effective occurrence of past speciation events. The comparisons between the Atlantic African and the North-Eastern Atlantic-Mediterranean geographic populations were unravelled using both Cytochrome Oxidase I and eight microsatellite loci. This approach guaranteed a robust dataset for the identification of a speciation event between the Atlantic African clade, corresponding to the ex Raja ocellifera nominal species, and the NE Atlantic-Mediterranean R. miraletus clade. As a matter of fact, the origin of the Atlantic Africa and the NE Atlantic-Mediterranean deep split dated about 11.74MYA and was likely due to the synergic influence currents and two upwelling areas crossing the Western African Waters. Within the Mediterranean Sea, particular attention was also paid to the transitional area represented by Adventura and Maltese Bank, that might have contributed in sustaining the connectivity of the Western and the Eastern Mediterranean geographical populations. Furthermore, the geology of the easternmost part of Sicily and the geo-morphological depression of the Calabrian Arc could have driven the differentiation of the Eastern Mediterranean Sea. Although bathymetric and oceanographic discontinuity could represent barriers to dispersal and migration between Eastern and Western Mediterranean samples, a clear and complete genetic separation among them was not detected. Results produced by this work identified a speciation event defining Raja ocellifera and R. miraletus as two different species, and describing the R. miraletus species complex as the most ancient cryptic speciation event in the family Rajidae, representing another example of how strictly connected the environment, the behavioural habits and the evolutionary and ecologic drivers are.