Ph.D. Dissertation Defense - Tullia Isotta Terraneo

Jun 11 2019 10:00 AM - Jun 11 2019 12:30 PM

TITLE: Diversity, phylogeography and taxonomy of hard-corals in the genus Porites from the Arabian Peninsula

ADVISOR: Professor Michael Lee Berumen

DATE: Tuesday, June 11, 2019

TIME: 10:00 a.m. – 12:30 p.m.

LOCATION: Building 3 - Level 5 - Room 5209


Abstract: In the last two decades, new molecular advances coupled with the study of skeletal microstructures, revolutionized our understanding of stony corals evolution. Yet, for some of the most ecologically important and diverse genera, such as Acropora, Montipora and Porites, taxonomy remains uncertain and still awaits revision. For these groups, more comprehensive criteria are required to untangle species boundaries and clarify evolutionary relationships. Evidence can be achieved embracing a unified concept of species, that integrates different operational criteria, or properties, to distinguish separate evolving lineages.

The genus Porites is one of the most important coral genera in terms of species diversity and panmictic tropical distribution. Moreover, it is considered one of the major hermatypic contributors to shallow reefs systems, and is often used as a model for ecological, physiological and paleoclimate studies. Yet, Porites is notorious for challenging taxonomic identification based on colony gross morphology, micromorphology, and single gene analyses, suggesting that the current classification poorly represents real evolutionary relationships. This severely undermines accurate assessment of biodiversity, and ultimately of the natural and anthropogenic cumulative impact that Scleractinia are facing worldwide. 

This research integrates skeletal morphological data and single locus genetic evidence, with genome-wide analyses, and alternative line of evidence to taxonomy (i.e. symbiotic association data), with the aim of clarifying biodiversity, biogeography, and taxonomy of Porites from the Arabian Peninsula, one of the hottest regions in the world. Indeed, the Arabian Peninsula is surrounded by some of the warmest and most saline seas on earth, making it a perfect model system in which evaluate the effects of global warming and climate change on reef ecosystems.

In this dissertation I firstly evaluated the diversity of Porites in the Red Sea and the Gulf of Aden providing a basic morpho-molecular background to the taxonomy of Porties in the region, highlighting that a. the current taxonomic and phylogenetic position of 12 Porites morphological species needs to be reassessed, and that b. coral biodiversity in the Arabian region needs to be re-evaluated. To address this, I reconstructed the complete mitochondrial genomes of two endemics species, contributing a solid framework for clarifying the phylogeny and taxonomy of Porites in future molecular studies. I implemented the previous morpho-molecular results with high throughput sequencing data, supplying a comprehensive hypothesis of species boundaries and biogeography of Porites in the Red Sea, Gulf of Aden, Gulf of Oman, and Arabian Gulf. These results evidenced that 15 morphological species are clustered into eight molecular lineages, two of which new to taxonomy and described for the first time in one of the papers derived from this dissertation. Finally, using the ITS2 marker coupled with NGS and the SymPortal framework, I presented evidence derived from symbiotic association of Porites with dinoflagellates in the family Symbiodiniaceae. Symbiont diversity showed patterns of geographic-specific association at Symbiodiniaceae genus, majority ITS2 sequence, and ITS2 type profile level. Specific associations with host-genotypes (but not morphological species) were also recovered, providing a further line of evidence that the current taxonomic framework is in urgent need for revision.

This dissertation highlights the utility of an integrated approach to taxonomy in elucidating species boundaries and phylogenetic relationships in Scleractinia and represents a framework that could be applied to other taxa awaiting revision, towards a better understanding of corals evolutionary history.

Bio: Tullia is originally from Italy, where she completed her Bachelor degree in Biological Sciences in 2013 at the University of Milano-Bicocca. In 2014 she moved to King Abdullah University of Science and Technology (KAUST) in Saudi Arabia, where she joined the Reef Ecology Lab of Prof. Michael Berumen. She completed her Master in Marine Science in December 2015 with the thesis “Species boundaries in the coral genus Goniopora from the Red Sea”. In her project, she used a reverse approach to taxonomy involving molecular and morphological evidence aimed at defining species boundaries in the hard coral genus Goniopora. She started her Ph.D. at KAUST in January 2016 under the supervision of Prof. Berumen, and, in the context of a co-tutelle program, she joined the ARC Centre of Excellence for Coral Reef Studies (James Cook University, Australia) in January 2017, where she works under the supervision of Prof. Andrew Baird. Her research focuses on clarifying species boundaries, evolutionary relationships, and biogeography of hard corals using evidence derived from morphological, genomic, symbiotic, and reproductive biology data.