Meeting Abstract
P1.17 Thursday, Jan. 3 Increased rates of sequence evolution in mites with parasitic lifestyles EDWARDS, D.D.**; VIDRINE, M.F.; ERNSTING, B.R.; Univ. of Evansville; Univ. of Evansville; Louisiana State Univ., Eunice de3@evansville.edu
Molecular phylogenetic studies for a broad range of taxa have revealed that rates of molecular evolution can vary widely within and among lineages and these variations have been correlated with body size, metabolic rate, generation time, and environmental temperature. A recently published phylogeny of Acari (mites and ticks) based on 18S and 12S rRNA sequence data revealed highly variable rates of sequence evolution both within and among lineages. Rates of sequence evolution were, however, significantly higher for mites and ticks when compared to rate differences among closely related non-mite taxa. Despite these observed patterns, the causes for the variable rates of sequence evolution remain unclear. Within certain animal lineages, there has been some evidence to suggest that species with parasitic lifestyles have higher rates of sequence evolution than nonparasitic species. To test this hypothesis for the Acari, we randomly selected 10 parasitic and 10 nonparasitic species with complete 18S rRNA sequence data and generated a distance tree for these taxa, using a closely related non-mite arachnid as the outgroup. Branch lengths of the tree generated by the analysis indicated an increased rate of nucleotide substitution among parasitic species. Furthermore, the average value of the p-distance (relative to the outgroup taxon) for parasitic mites was significantly greater than that observed for nonparasitic taxa. Together, these results suggest that mites with parasitic lifestyles exhibit higher rates of sequence evolution than those that are nonparasitic. Future studies will examine the relative rates of synonymous versus nonsynonmous nucleotide substitutions for coding genes between these two groups of mites to determine the degree to which selection plays a role in generating higher rates of sequence evolution among parasitic taxa.
