Creation of a Species-Level Cephalopod Phylogeny to Resolve Major and Minor Clades

Abstract

The Cephalopods (Mollusca:Cephalopoda) are a class of animals consisting of about 800 species that demonstrate incredible morphological and ecological diversity. However, the taxonomic relationships of and between many groups of cephalopods are not fully resolved. Previous studies have identified many areas in which the systematics within various groups are ambiguous, and have often been low resolution, corresponding with equivocally separated clades. This is often due to limitations in taxon sampling; comprehensive taxon sampling at the species level allows us the opportunity to examine the phylogenetic relationships within and between various major and minor clades of cephalopods. Major clades within the order Oegospida have been resolved, but due to limited sampling, minor clades still have yet to be resolved. Furthermore, it is still unclear what the relationship of the subfamily Sepiolinae is with the rest of the Sepiolidae. Along similar lines, the relationships of the cirrate octopuses to Octopoda have also not been thoroughly resolved. In this project, we created a global species-level phylogeny of cephalopods using previously published short-read genetic data. Ultimately, this phylogeny will give us insight into the evolutionary relationships within Cephalopoda, including many groups that have been understudied. In addition, this tree may also elucidate the dynamics of convergent evolution, complex trait evolution, and the underlying selective pressures and ecological strategies that influence diversification. Ongoing work involves using this tree as a basis to study how bioluminescence originated and evolved within this group. We will be performing parsimony-based ancestral state reconstruction to see how many times various components of bioluminescent organs originated at the organismal and subcellular level within Cephalopods.