Phylogenetics and Biogeography of Aeglidae

Brigham Young University, Provo UT

Investigators

Abstract

0075600 Crandall Over 70 species and subspecies of freshwater crabs from the family Aeglidae (Decapoda: Anomura) are known to be endemic to southern South America. These crabs are an interesting and unique group to study because of (1) the unusual distribution of species diversity: aeglids are the only anomurans restricted to freshwater; (2) their morphological peculiarities: they have not developed pleopods (these are the 5 pairs of appendages on the ventral abdomen), the carapace is subdivided by lines, and the gill structure is trichobranchiate (divided into three branches); (3) the ecological importance of crabs to freshwater ecosystems, and the fact that many of the known species may be considered endangered or vulnerable; and (4) the role they play in limiting crayfish dispersion. Despite the attraction of this group for evolutionary study, there has been no work on its phylogenetic relationships. This proposal represents the first detailed attempt to discover the evolutionary relationships of Aeglidae. This study will sample all the speices of the family and some of their anomuran relatives Galatheidae, Porcellanidae and Chirostylidae (Galatheoidea), which will serve as outgroups to test the monophyly of the Aeglidae. Seven mitochondrial and nuclear genes will be screened to survey approximately 7800 bp of sequence data. Thus phylogenetic analysis will comprise multiple DNA regions separated and combined using maximum parsimony, neighbor-joining and maximum likelihood, and combinations of these methods with the Templeton, Crandall, and Sing (TCS) method. Recovering a robust phylogenetic hypothesis for Aeglidae will provide a framework on aeglid systematics upon which we can test several hypotheses. For example, what is the taxonomic position of Aeglidae in the Galatheoidea? Did Aeglidae speciation occur from north to south or from west to east or some combination? What are the biogeograpical histories of the river drainages in which aeglids occur? Of the previously identified regions of endemism of freshwater stream organisms, what are the conservation priorities for these regions? Preliminary results and future phylogenetic relationships established from this study, primer sequences, PCR conditions and color photos of each species will be incorporated in a new freshwater crab web page that will be created in the KAC lab as part of the Tree of Life web project (http://ag.arizona.edu/tree/). This will contribute to integration of research and education at all school levels. This project will also provide collaborations with Brazilian and Chilean biologists, and training for at least one postdoctoral research associate and one undergraduate student at Brigham Young University.