Meeting Abstract
In many terrestrial ecosystems, earthworms (Crassiclitellata) constitute the main component of animal biomass, serve as critical links in food webs and play a vital role as soil ecosystem engineers. Unfortunately, the relative simplicity of the earthworm body plan has made morphology-based inference of crassiclitellate phylogeny difficult. Recent molecular analyses using PCR-amplified loci have yielded key insights, but to date, genome-scale data have not been used to study crassiclitellate phylogeny. To bring more loci to bear on the remaining challenges in crassiclitellate systematics, we generated transcriptomes for members of ~40 crassiclitellate genera representing fifteen families as well as six outgroups and implemented a progressive approach to infer orthology and test possible sources of bias. Our trees are broadly congruent with previously published molecular phylogenies—we recovered two major crassiclitellate clades, one comprising Criodrilidae, Hormogastridae, Lumbricidae and Lutodrilidae, and the other comprising Microchaetidae and all other crassiclitellates in our data set. However, there are also several differences—we found strong support for the hypothesis that Crassiclitellata is a subgroup of a paraphyletic Haplotaxidae, and uncertainty remains regarding the position of Moniligastridae, possibly rendering Crassiclitellata paraphyletic. While confirming the main nodes obtained with smaller datasets, our results indicate that we need to look more closely at relationships in the crown group Megascolecoidea, the basal branches of Crassiclitellata, and the relationship of earthworms to other clitellates.
