Meeting Abstract

P3.195  Friday, Jan. 6  Evaluating the phylogenetic utility of alg11, a potential marker for sponge systematics SALAZAR, J*; CARMACK, CA; THACKER, RW; Ohio State Univ; Univ. of Alabama at Birmingham; Univ. of Alabama at Birmingham

Studies of molecular systematics using nuclear protein-coding genes are often limited by the need to amplify markers from RNA or cDNA. Recently, alg11 (which encodes the asparagine-linked glycosylation 11 protein, also known as alpha-1,2-mannosyltransferase in yeast) has been proposed as a novel phylogenetic marker for resolving relationships among sponges, with the advantage of being amplified directly from genomic DNA extractions (Huchon, personal communication). To date, this marker has been examined in 13 specimens of Porifera, including 5 demosponges and 3 calcareous sponges. We sought to evaluate the phylogenetic utility of alg11 by increasing the diversity of sponges sampled. Proposed alg11 primers were tested using 35 specimens representing 32 genera of sponges. alg11 was amplified from 24 of the 35 specimens, with higher success from Demospongiae than from Calcarea. High-quality sequences were obtained for 21 specimens, with an average p-distance of 43.7% for nucleotide sequences and 72.7% for amino acid sequences. In contrast, for these same specimens, a 28S nuclear ribosomal gene fragment displayed an average p-distance of 12.9%. The higher variability of the alg11 sequences resulted in a phylogeny with longer terminal branches and weaker node support values than obtained from 28S fragments. Although the 28S topology reflected current views of sponge classification, the alg11 phylogeny placed closely related taxa into disparate clades; concatenating alg11 with 28S did not improve this lack of phylogenetic signal. Our results suggest that novel phylogenetic markers require evaluation at multiple taxonomic scales, using specimens that reflect the broader diversity of a particular taxonomic group.