Meeting Abstract
During the 2014 and 2015 California Academy of Sciences expeditions to the Philippines, advanced SCUBA technology allowed our research to explore deep reefs of the “Twilight Zone”. Formally called the mesophotic zone, this low light area from 60m-150m contains a wealth of poorly studied or completely undiscovered species. The purpose of this study was to investigate the molecular phylogeny of nine likely undescribed nudibranch species from the genus Halgerda collected during this expedition, most of which were collected from the mesophotic zone. Mitochondrial fragments cytochrome c oxidase I (COI) and 16S as well as nuclear fragments H3 and 28S were sequenced from 34 samples of Halgerda species, including the nine recently discovered species and previously un-sequenced species such as Halgerda formosa (the type species), Halgerda batangas, and Halgerda tessellata. Outgroups were chosen from among several other discodorid exemplars. The phylogeny was determined using maximum likelihood and Bayesian analyses. The results confirm that eight of the nine suspected new species are indeed distinct from described species. Molecular data were lacking from the ninth species owing to its fixation in a formalin-based fixative. The data also suggest that the undescribed species from the mesophotic zone form a clade nested within Halgerda. This also suggests a single invasion of the mesophotic zone by a shallow-water ancestor and subsequent radiation of this lineage within the mesophotic. This is different from what was found with mesophotic fish in the genus Chromis, in which four new mesophotic species each had a different shallow-water sister species.
