jump to navigation

Introduction April 30, 2011

Posted by cjcd in Uncategorized.
1 comment so far

The snail family Pleuroceridae is a large and diverse taxon with an often-modified taxonomy and murky phylogenetic relationships.  The genus Elimia is the largest of those in Pleuroceridae and also the most common in the state of Alabama. A formidable list of synonymies and other taxon changes have been accumulated in the ongoing debates over the taxonomy of the genus, which effects real world conservation efforts (for instance, if an endangered species is found to be synonymous with a more numerous species, recovery efforts like the introduction of colonies could be halted). Using DNA and amino acid sequence analysis of the mitochondrial cytochrome c oxidase subunit I protein, I have attempted to better delineate Pleuroceridae’s and specifically Elimia’s phylogenetic relationships.

The shell of a specimen of Elimia cahawbensis, a species used in this project.

Cytochrome c oxidase subunit I (COI) was used for sequence analysis because previous studies have shown that divergences in COI sequences are substantive enough to distinguish between closely related species in all animal phyla save cnidarians (Hebert, Ratnasingham, and deWaardes, 2003). COI sequence similarity has been used to infer the phylogeny of Pleurocerid species before, specifically Elimia foremani, a species used in this project (Sides, 2005). Gastropods are especially well suited to COI analysis due to a large amount of sequence length variation compared to other invertebrate groups (Hebert, Ratnasingham, and deWaardes, 2003).

Apart from the outgroup species, Caridina indistincta (a small shrimp), seven non-elimia species were also analyzed. Three of these were members of genus Pleurocera and three were members of genus Leptoxis. Both of these are genera are in the same family as Elimia, and there have been suggestions of combining Pleurocera and Elimia into one genus (Dillon, 2011). Hypotheses included all the Elimia, Pleurocera, and Leptoxis species clustering into three distinct groups, supporting the current taxonomic groupings, and the Elimia and Pleurocera clustering together, supporting the argument for clumping the two genera together.

The shell of a specimen of Leptoxis plicata, a species used in this project.

The shell of a specimen of Pleurocera canaliculatum, a species used in this project.