Meeting Abstract
Cladobranchia (Gastropoda: Nudibranchia) is a diverse (~1000 species) but understudied group of sea slug mollusks. In order to fully understand the ecological and morphological character evolution as well as the importance of nudibranchs within Cladobranchia, a solid understanding of the evolutionary history of this group is necessary. This goal has yet to be achieved, as to date there have only been two direct attempts at resolving the evolutionary relationships of members within this group, with neither identifying a well-supported topology. Even at the most fundamental level, it is unclear whether the three traditional groupings within Cladobranchia (Arminida, Dendronotida and Aeolidida) are monophyletic. In our research, we have successfully addressed some of these long-standing issues in resolving the evolutionary history of Cladobranchia utilizing RNA-Seq data (transcriptomes). We sequenced 16 transcriptomes of cladobranchs from 16 different genera de novo and combined these with four transcriptomes from the NCBI Sequence Read Archive. Transcript assembly using Trinity and orthology determination using HaMStR yielded 839 orthologous groups for phylogenetic analysis under a maximum likelihood framework. These data provide a well-supported and almost fully resolved phylogenetic hypothesis of the sampled taxonomic groups in Cladobranchia. Our results support the monophyly of Cladobranchia and the sub-clade Aeolidida, and show that Dendronotida is paraphyletic. The data collected also resolve the position of problematic groups and revealed some interesting familial level relationships. However, broader taxon sampling will be necessary before we propose any taxonomic modifications within Cladobranchia.
