Systematics and Evolution of Nematode Family Rhabditidae

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DEB-9981632David H. FitchDr. David H. Fitch at New York University has been awarded a grant to study the evolutionary relationships among species in the nematode family Rhabditidae. Habitat diversity and sheer abundance alone make Rhabditidae an important taxon, yet it is one of the most poorly understood animal groups in terms of biodiversity, phylogeny and evolution. Recent evidence suggests that some agriculturally important parasites arose within Rhabditidae, elevating the importance of these otherwise "free-living" nematodes for research on the origins of parasites or directing searches for free-living models closely related to parasites. Moreover, the family includes Caenorhabditis elegans, whose use as a model in developmental genetics has made that species one of the most intensively studied animals on Earth. A phylogeny is required to test generalizations from this model and to bootstrap information on genome functionality from C. elegans to other Rhabditidae and other metazoan systems. The phylogeny will also be required to test possible correlations between form and behavior, such as those between evolutionary changes in male tail morphology and male copulatory behavior. Such correlations may to provide insight into possible preadaptations and modes of selection resulting in the diversity of rhabditid forms.Morphological and molecular data will be used to infer a phylogeny for Rhabditidae. Robust homology criteria derived from recent developmental and ultrastructural studies will be used in the analysis of morphological characters, such as features of the male copulatory bursa ("male tail"). Morphological data for all known (and some still-undescribed) taxa will be compiled in a collaboration with renowned rhabditid zoologist Walter Sudhaus (Freie Universitat Berlin). Molecular data will be collected for at least two loci known to be phylogenetically informative at this taxonomic level, nearly complete sequences of 18S ribosomal RNA genes and partial sequences from the RNA Polymerase II locus. Preliminary data suggest that all three data partitions provide congruent phylogenetic information, thus allowing a "total evidence" approach to reconstruct rhabditid phylogeny.