Meeting Abstract
Although recent phylogenomic studies employing hundreds of nuclear protein-coding genes have greatly improved understanding of mollusc class-level phylogeny, placement of some lineages such as Scaphopoda and Monoplacophora remain unsettled. We investigated whether ultraconserved elements (UCEs), putative regulators of animal gene expression with very low rates of sequence evolution, could be used as an alternative to nuclear protein-coding genes. To this end, we downloaded publicly available genomes from ten molluscs (six bivalves, three gastropods, and one cephalopod) and five outgroup taxa (two annelids, one brachiopod, one phoronid, and one nemertean) and screened them for UCEs following established approaches as implemented in PhylUCE. This approach identified 4,759 UCEs shared among at least ten taxa and 325 shared across all fifteen taxa. Using a test set of the 529 UCEs with no less than 70% data completeness, we assembled and analyzed a matrix with 142,817 nucleotide positions. Maximum likelihood analysis in RAxML using the GTR+G4 model yielded a tree with strongly-supported relationships that are largely consistent with the current understanding of molluscan evolution. Thus, these preliminary results indicate that this approach has promise for resolving lingering debates about mollusc class-level phylogeny. To this end, we are expanding this dataset to include other public datasets and new genomic data from representatives of three other molluscan classes.
