Meeting Abstract

6.1  Monday, Jan. 4   Conflicting Evolutionary Hypotheses from the Analysis of 10 Glass Sponge Mitochondrial Genomes HAEN, K.M.*; LAVROV, D.V.; Iowa State University; Iowa State University khaen@iastate.edu

Although progress has been made toward understanding the phylogenetic relationships among the early branching metazoan clades (the Porifera, Cnidaria, Ctenophora and Placozoa), the resolution of their relationships has been fraught with difficulty due to biological and evaluative factors. These include sparse taxonomic sampling, unequal rates of evolution across lineages and mutational saturation (computationally, the long branch attraction artefact). The analysis of mitochondrial (mt) genomes is useful for investigating animal relationships but is also interesting from a more general evolutionary perspective. Mt genomes can contain rare genomic changes that are believed to be valuable for phylogenetic inference. These include gene rearrangements, variations in the genetic code, differences in the secondary structures of encoded transfer and ribosomal RNAs, overlapping genes, and the presence of ribosomal frameshifting sites in protein coding sequences. Glass sponges (Class Hexactinellia, Phylum Porifera) have represented one of the final frontiers for mitochondrial genomic data in the context of the early branching metazoa. We have increased the number of hexactinellid complete mt genome sequences from the three previously published genomes to 10, including individuals from six taxonomic families in our sampling. Here we present well-supported, but confounding, topologies at the base of the phylogenetic tree when evaluating the position of glass sponges within the metazoan tree of life. We then discuss the observation that many apparently “rare” genomic changes found in the mitochondrial DNAs of glass sponges and distantly related taxa seem to be prone to convergence.