The evolutionary relationship of the Millepores in the Caribbean has been problematic for years. Taxonomic classification of these Millepores is based upon habitat and morphology. Two distinct morphologies, classified as separate species, have been recorded, but extensive phenotypic plasticity yields a large variety of intermediate morphologies that do not fit into the current taxonomic groupings. DNA was collected from a wide range of Millepora growth forms and the internal transcribed spacer (ITS) region of ribosomal DNA (rDNA) was sequenced. A phylogenetic tree derived from 36 rDNA sequences showed that the Millepores separated into two distinct clades independent of depth, reef location and growth form. However, rDNA occurs in tandem repeats, and a major concern with using rDNA in phylogenetic analyses is the existence of variability within the repeated units of single individuals. Sequencing results of replicates of a single individual indicate that there is little intragenomic variability within the ITS regions. Denaturing gradient gel electrophoresis of PCR-amplified rDNA demonstrates the existence of a dominant rDNA form and a rare variant rDNA form, confirming our sequencing analysis. These results indicate that using the ITS region for phylogenetic analysis is accurate as long as intragenomic variability is assessed
Currently, we are examining whether ribosomal RNA (rRNA) secondary structure of the ITS regions is useful in establishing phylogenetic relationships. Functional ITS regions fold to form secondary structures that can be used as diagnostic indicators of taxonomic difference. We hope these efforts lead to a comprehensive understanding of the phylogenetic relationships of the Millepores.
Sophie Gaynor, ’12
Majors: Mathematics and Statistics, Biology
Benjamin Alleva, ’13
Major: Biochemistry and Molecular Biology
Sponsor: Craig Tepper