BABBITT, C.C.*; PATEL, N.H.: Developmental Systematics: Correlation Between Ontogeny and Phylogeny in the Malacostraca (Crustacea)

Although events in early development have long been used as defining characters for taxonomic groups, the phylogenetic signal of different developmental processes at different taxonomic levels has never been rigorously tested. The challenge has been to define distinct processes during development as independent characters for phylogenetic analysis. To address this we are defining and testing a variety of possible characters of early development, from cleavage to segment identity formation, for phylogenetic signal. Specifically, this analysis is focused on using arthropod segmentation as the archetype of a modular developmental character as measured by protein staining of segmentation and segment identity genes. The examination of different character coding schemes with both traditional (presence/absence) and morphometric data will be discussed. For a background framework with which to test developmental character congruence we have constructed a preliminary molecular phylogeny using 18S and 28S rDNA sequences. This framework, combined with dense taxon sampling within the Malacostraca, allows for an examination of where putative developmental characters are informative taxonomically. From this we are working to produce a model of if and where early developmental mechanisms have been influential in the evolution of the Malacostraca. By looking at the evolution of developmental processes in a hierarchical framework, arguments can be made of what types of developmental characters influence morphological evolution. Just as the understanding of what genes were informative at different taxonomic levels was informative for both phylogenetics and molecular evolution, this type of character-based approach using development may yield similar benefits for both systematic and evodevo studies.