Taxonomic revision of Mediterranean sponge species of the genus Hexadella through cytology, chemistry and molecular sequences in an integrative approach
Allewaert, C. (2010). Taxonomic revision of Mediterranean sponge species of the genus Hexadella through cytology, chemistry and molecular sequences in an integrative approach. MSc Thesis. Station Marine d'Endoume, Centre d'Océanographie de Marseille/Universiteit Gent; Faculteit Wetenschappen; Afdeling Mariene Biologie: Gent. 80 pp.
Given the prevalence of cryptic species within marine sponges, only a fraction of their true biodiversity has been described. Over the recent decades, molecular biology has proven to be an excellent tool for rapid identification of cryptic speciation and a large amount of species have been uncovered. These findings should however incorporate diagnostic characters, hereby validating the existence of the species. In a recent phylogenetic study on Hexadella species, molecular genetics have once more played a decisive role in the discovery of unexpected biodiversity. Previous H. pruvoti was found to consist of two genetically divergent lineages; H. pruvoti and H.cf. pruvoti. In the same way, former H.racovitzai revealed two divergent haplotypes, H. racovitzai and H.cf. racovitzai. Given the non visual communication of this raw molecular data, this study investigates possible discriminating factors in order to make the species ready available for scientists. Using previous DNA database as reference framework, our study is based on 27 newly sampled Hexadella species from four Mediterranean sites.Hexadella representatives lack of skeleton, making conventional spicule-based taxonomy impossible. After correlating the collected species with their respective haplotypes through DNA sequencing, morphology, cytology and chemistry chosen as prime methods for species distinction, showed to be highly efficient in the systematics of the four species. This study is a good example, demonstrating the possibility of discriminating genetically revealed cryptic through comparative integrative taxonomy. Without the combination and synergy of these disciplines, no robust classification of the new species would have been achieved and therefore this work strongly recommends to haunt comparative integrative taxonomy as new framework for Hexadella species identification. Species fiches as well as an identification key to the four Hexadella species are here provided.
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