Systematics, taxonomy and phylogenetic relationships of the coral family Lobophylliidae

Traditional classification of scleractinian corals (Cnidaria, Anthozoa, Scleractinia) have been conducted on the basis of skeleton macromorphology. However, the commonly used skeletal characters are plagued by phenotypic plasticity, intraspecific variation, and morphological convergence that fail to recognize most natural evolutionary lineages. Recent molecular studies have revolutionized the conventional taxonomic schemes, suggesting remarkably different phylogenetic relationships when compared with those based on macromorphology. In the last decade, the integration of this increasing amount of genetic data and new micromorphological and microstructural traits has led to a better understanding of evolutionary relationships between hard corals and opened the way to the new era of coral taxonomy. The Indo-Pacific family Lobophylliidae potentially represents an interesting case study of “reciprocal illumination” between genetics and morphology. This taxon has been defined on a combination of phylogenetic analyses and micromorphological observations, although it still remains poorly understood.This dissertation aims to fill this gap in knowledge through the investigation of evolutionary relationships of the Lobophylliidae and starting the impending process of taxonomic revision of this family as a result of an integrated molecular and micromorphological approach. A molecular phylogeny of one of the three major groups recovered in the order Scleractinia, the Robusta, to which the Lobophylliidae belong is presented. The representatives of this family were recovered in a cohesive lineage for the first time and the phylogenetic relationships with the other closely related families were discussed. The analysis was then expanded analyzing more species and samples and focused exclusively on the Lobophylliidae in order to produce the most comprehensive molecular phylogeny reconstruction of this group to date. The monophyly of the family was strongly supported and nine main monophyletic genus-level lineages were recovered within the Lobophylliidae. All analyzed polytypic genera, were not monophyletic and resulted in need of a formal taxonomic revision. Subsequently, the complete mitochondrial genome of Acanthastrea maxima was sequenced. This species based on a combination of data including its restricted geographic distribution, evolutionary distinctiveness, and small population size was revealed be a case of priority for future conservation strategies. Being 18,278 bp in length, it is the longest sequence among the robust corals sequenced mitogenome to date, while the GC content and the gene arrangement are similar to those of the other scleractinian corals. Finally, integrating multi-locus molecular phylogenies and detailed gross- and fine-scale morphologic observations three cases analyzed in the family provided examples of how reverse taxonomy can be useful in understanding the evolutionary history of the Lobophylliidae: I) a taxonomic revision for the monotypic genus Australomussa, revealed to be a junior synonym of Parascolymia, was proposed; II) the long-ignored monospecific genus Sclerophyllia was resurrected and the unforeseen sister relationships between Sclerophyllia margariticola and A. maxima led to the placement of the latter species in Sclerophyllia; III) the closely related genera Homophyllia and Micromussa were revised with the description of two new species of Micromussa and Symphyllia wilsoni, an Australian endemism, was placed in a new genus based on an unique combination of molecular and micromorphological data. Overall, the results stemming from the results obtained in the framework of my thesis significantly improve our understanding of evolution of the family Lobophylliidae and provide a solid case for the importance of an integrated morpho-molecular approach in resolving taxonomy of this group of marine animals.