Bridget Vincent

Cephalopod photophores: estimating the origins of complex convergent traits

Authors: BA Vincent, ES Lau, SV Ramamurthy, TH Oakley

Convergent traits arise when distantly-related taxa independently develop similar phenotypes. However, the origins of these traits can be difficult to estimate, especially in complex traits which are not governed by a single gene. Determining where these traits originate is key in understanding their evolutionary history and how patterns of convergence persist in multiple levels of biological organization. Bioluminescence is a convergent, complex trait present across taxa in both marine and terrestrial species, including the class Cephalopoda. The organ producing bioluminescence (photophores) shows extensive morphological diversity across both taxa and biological levels. Different species of cephalopods may have bacteriogenic photophores (organs whose symbiotic bacteria produce light) or autogenic photophores (organs that produce light using their own cells) in varying degrees of complexity. Though we know cephalopod bioluminescence is convergent, the number of independent origins of these complex traits is a mystery. We performed parsimony-based ancestral state reconstruction on a previously published genus-level cephalopod phylogeny and found at least 10 origins of cephalopod photophores (3 bacteriogenic and 7 autogenic). Ongoing work includes building a species-level phylogeny using published short-read genetic data, transcriptomes, and genomes to assess whether a higher resolution affects our estimates of evolutionary origins. Additionally, we are gathering morphological data for each species’ photophore to perform ancestral state reconstruction on cellular and tissue-level characters. This will allow us to determine if patterns of convergence remain consistent across biological levels in a complex trait. 

See Bridget's poster during the Poster Session on Friday (2/5, ~4:30pm PST)!