title: Phylogenomics reveals deep molluscan relationships.
abstract: Evolutionary relationships among the eight major lineages of Mollusca have remained unresolved despite their diversity and importance. Previous investigations of molluscan phylogeny, based primarily on nuclear ribosomal gene sequences or morphological data, have been unsuccessful at elucidating these relationships. Recently, phylogenomic studies using dozens to hundreds of genes have greatly improved our understanding of deep animal relationships. However, limited genomic resources spanning molluscan diversity has prevented use of a phylogenomic approach. Here we use transcriptome and genome data from all major lineages (except Monoplacophora) and recover a well-supported topology for Mollusca. Our results strongly support the Aculifera hypothesis placing Polyplacophora (chitons) in a clade with a monophyletic Aplacophora (worm-like molluscs). Additionally, within Conchifera, a sister-taxon relationship between Gastropoda and Bivalvia is supported. This grouping has received little consideration and contains most (>95%) molluscan species. Thus we propose the node-based name Pleistomollusca. In light of these results, we examined the evolution of morphological characters and found support for advanced cephalization and shells as possibly having multiple origins within Mollusca.
authors: Department of Biological Sciences, Auburn University, 101 Rouse Life Sciences, Auburn, Alabama 36849, USA. kmkocot@auburn.edu
authors: Kevin M
authors: KM
authors: Kocot
authors: Johanna T
authors: JT
authors: Cannon
authors: Christiane
authors: C
authors: Todt
authors: Mathew R
authors: MR
authors: Citarella
authors: Andrea B
authors: AB
authors: Kohn
authors: Achim
authors: A
authors: Meyer
authors: Scott R
authors: SR
authors: Santos
authors: Christoffer
authors: C
authors: Schander
authors: Leonid L
authors: LL
authors: Moroz
authors: Bernhard
authors: B
authors: Lieb
authors: Kenneth M
authors: KM
authors: Halanych
mesh_terms: D000818:Animals; D049872:Bivalvia / Q000033:anatomy & histology / Q000145:classification / Q000235:genetics; D020224:Expressed Sequence Tags; D049851:Gastropoda / Q000033:anatomy & histology / Q000145:classification / Q000235:genetics; D020869:Gene Expression Profiling; D005796:Genes; D016678:Genome / Q000235:genetics*; D023281:Genomics; D008954:Models, Biological; D008974:Mollusca / Q000033:anatomy & histology / Q000145:classification* / Q000235:genetics*; D010802:Phylogeny