The presentation is titled Mitochondrial genome evolution and differential gene expression in the pan-tropical sea urchin Tripneustes gratilla.
In order to better characterize the placement of genus Tripneustes, as a representative of the Toxopneustidae family within the broader sea urchin mitochondrial (MT) phylogeny, the complete MT genome of Tripneustes gratilla has been generated and compared with all published echinoid MT genomes currently available on NCBI GenBank. A complete MT genome phylogenetic tree supports the existence of the superfamily Odontophora (consisting of the families Strongylocentrotidae, Echinometridae, and Toxopneustidae). A relaxed molecular-clock time calibration, with 8 fixed calibration points, of a MT genome phylogenetic tree suggests a split between the three key Odontophore MT lineages occurred during the late Eocene/Oligocene. This time frame is marked by major global oceanographic changes, which could drive species divergence through positive selection. Rate of gene evolution of individual MT genes is assessed through pairwise as well as a branch-site comparison of non-synonymous to synonymous substitution ratios. Models of positive selection and neutral evolution, as compared via a likelihood ratio test, show no evidence of strong positive selection on mitochondrial genes at the genesis of the Odontophora. This suggests MT markers within the echinoidea are generally robust to large-scale selection events and can still serve as valuable markers for species level relationships.
Picture of Tripneustes gratilla from Wikimedia commons - By Philippe Bourjon - Don de l'auteur, CC BY-SA 3.0,