9806368 Dick The Bryozoa (Ectoprocta) comprise a phylum of colonial animals broadly distributed worldwide in marine and freshwater benthic habitats. Colonies, which are readily visible, are composed of hundreds or thousands of tiny zooids, each less than a millimeter long. There are an estimated 6,000 living species and over 15,000 described fossil species. The largest group containing living bryozoan species is the class Gymnolaemata, currently divided into two orders: Ctenostomata and Cheilostomata. Ctenostomes have zooids with uncalcified walls, whereas cheilostomes have calcified walls. The large majority of living bryozoan species are cheilostomes, which have undergone a great radiation since their appearance approximately 145 million years ago. Because of their extensive fossil record, considerable diversity, and broad distribution, cheilostomes have been very important in evolutionary and ecological studies. However, correct interpretation of these studies depends upon a reliable knowledge of evolutionary relationships among cheilostomes. Reconstructing this phylogeny using morphological characters has been exceedingly difficult, due to high levels of convergence among characters. To begin to remedy this problem, this study will gather DNA sequence data from bryozoans and perform cladistic analyses to reconstruct phylogeny. Preliminary work utilizing a partial sequence of the mitochondrial, large-subunit 16S rRNA gene has suggested that cheilostome phylogeny is likely to be complex, and inseparable from a broader consideration of gymnolaemate phylogeny. The goals of this study are 1) to utilize sequences from the nuclear 18S rRNA gene to determine whether the Gymnolaemata are a monophyletic group in the context of a higher-level bryozoan phylogeny, and to reconstruct higher-level relationships among ctenostome and cheilostome bryozoans, and 2) to utilize sequence data from both the 18S rRNA gene and the mitochondrial 16S rRNA gene to reconstruct superfamily- level relationships among cheilostomes.
