Meeting Abstract
Over evolutionary timescales, many marine taxa have made transitions to and from the deep sea. Shallow and deep-sea habitats vary drastically in several environmental variables including light, temperature, oxygen concentration, pressure, and pH. Ctenophores, also called comb jellies due to their large ciliary paddles arranged in “comb rows,” are monophyletic but deep and shallow species are spread across the ctenophore phylogeny, suggesting transitions from deep to shallow and from shallow to deep have occurred multiple times. To understand the evolutionary pressures that drive adaptation to extreme environments, we collected 35 ctenophore species with representatives from a diverse set of ctenophores with habitats ranging from surface waters to 4000 meters deep. Our process involves sequencing and assembling transcriptomes, defining orthologs, estimating phylogenies, detecting positive selection, and identifying convergence in protein sequences. Using these data we are determining: (1) the phylogenetic relationships among these species, (2) the evolutionary lineages where depth transitions have occurred, (3) the depth range for the ancestral ctenophore and (4) the evolutionary genetic changes that have allowed species to adapt to shallow and deep sea habitats. This work uncovers a great mystery of how animals can adapt to extreme environments, and will provide a baseline of deep-sea ctenophore biodiversity, which will be important for understanding ecological change in the face of anthropogenic stressors.
