Phylogenomic investigation of molluscan evolutionary relationships

Meeting Abstract

26.2  Wednesday, Jan. 5  Phylogenomic investigation of molluscan evolutionary relationships KOCOT, Kevin M.*; CANNON, Johanna T.; TODT, Christiane; KOHN, Andrea B.; CITARELLA, Mathew R.; MEYER, Achim; SCHANDER, Christoffer; SANTOS, Scott R.; MOROZ, Leonid L.; LIEB, Bernhard; HALANYCH, Kenneth M.; Auburn University; Auburn University; University of Bergen; Whitney Laboratory for Marine Biosciences; Whitney Laboratory for Marine Biosciences; Johannes Gutenberg University; University of Bergen; Auburn University; Whitney Laboratory for Marine Biosciences; Johannes Gutenberg University; Auburn University

Despite their diversity and importance, little is known about the evolutionary relationships among the 8 major lineages, or classes, of Mollusca. Because of their extreme morphological disparity, numerous conflicting phylogenetic hypotheses have been proposed. To date, molecular investigations of molluscan phylogeny have relied primarily on nuclear rDNA. Unfortunately, such approaches have been unsuccessful at robustly reconstructing the phylogeny of this group. However, phylogenomic studies, which employ large amounts of sequence data from genomes and/or expressed sequence tag (EST) libraries, are advancing the field of systematics. In order to investigate molluscan phylogeny using a phylogenomic approach, we sequenced ESTs from 18 diverse molluscs using 454 pyrosequencing. In combination with publicly available data, a total of 42 molluscs plus 15 outgroups were analyzed. Building on existing bioinformatics tools, we developed a pipeline to trim, assemble, translate and parse sequences into putatively orthologous groups (OGs). Custom scripts were utilized to remove groups and/or sequences with dubious orthology or quality and a final supermatrix consisting of 348 OGs was assembled. A maximum likelihood analysis of our dataset strongly supports Aculifera (chitons + aplacophorans) within a monophyletic Mollusca. Aplacophora (Neomeniomorpha + Chaetodermomorpha) is also supported. Within Conchifera, scaphopods were placed as a sister to a gastropod-bivavle clade. Hypotheses regarding the polarity of morphological characters important to our understanding of molluscan evolution will be evaluated in light of these results.

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