Seminar Series 2005

DNA barcodes and application of identification of bivalve larvae

Dr Jonathan Geller
Moss Landing Marine Laboratories, California

Identification of invertebrate larvae in natural plankton samples is notoriously difficult because complete life cycles for most species are not described. This difficulty in turn hampers ecological and environmental studies of benthic communities because variation in larval supply cannot be quantified. We investigated the use of DNA markers to identify larvae of five bivalve species in the waters within and near Morro Bay, California. Mitochondrial Cytochrome oxidase subunit I (COI) has been promoted as a universally applicable barcode for biodiversity studies. We sequenced COI in these five species and in congeners suspected to co-occur in our plankton samples. Contrary to expectation, COI sequences did not resolve monophyletic group corresponding to recognized species boundaries, indicating that COI was not appropriate for design of species-specific DNA markers. In contrast, groups within phylogenetic trees based on mitochondrial Cytochrome oxidase b corresponded to expected species boundaries, and we therefore experimented with several approaches for sequence detection to apply to our plankton samples. We present results of molecular analysis of a subset of our complete plankton sampling program and demonstrate the application of "DNA barcodes" in an environmental study. In general, our experience suggests caution in the use of a single locus in barcode projects. I will also briefly discuss the aims of my present visit to the Gump Station, which is to explore the feasibility of functional genomic approaches to ecological and evolutionary research at relatively remote field stations.