Developmental systematics: Synthesizing ontogeny and phylogeny in the Malacostraca (Crustacea).

摘要

Studies of the role of developmental mechanisms in evolution need a common language---the language of systematics---to bring them into a truly comparative and evolutionary framework. By first understanding developmental (ontogenetic) processes in a larger systematic (phylogenetic) framework, "developmental systematics" can provide novel information about both evolution and development. The goal of this thesis is to explore experimentally what a developmental (ontogenetic) character is, and to analyze how these characters can shed light on the evolution of development of a specific group.; To this end, I have defined and collected developmental characters from a taxonomically diverse group of malacostracan crustaceans. I then examined this developmental data set by congruence with a large molecular (18S and 28S rDNA) data set, which I also sequenced and analyzed separately. The Malacostraca is an excellent group in which to explore these questions, as it is a morphologically diverse class, with approximately 80,000 described species, and a rich embryological literature.; Developmental characters have not been rigorously evaluated for multiple groups over a series of ontogenetic stages before. Because of this, the specific questions I need to address are: What is a developmental character? At what taxonomic levels are these characters informative? What can these characters tell us about the evolution of development?; In the first chapter, I present an overview of past approaches to synthesizing ontogeny and phylogeny. Then I present my argument that developmental events need to be rigorously defined as localized semaphoronts at a specific developmental time and biological level. Chapter two consists of my molecular phylogenetic analysis of the Malacostraca, which was done both because of a lack of molecular phylogenetic data for this group, as well as to be a framework against which to compare my developmental phylogenetic hypotheses. Chapter three is the compilation of the raw developmental data, the characters built from that data set, and the phylogenetic hypotheses created solely from the developmental data. In chapter four I evaluate my argument from chapter one, based on empirical developmental data, and explore how these specific characters have evolved over the 500 million years that separate these malacostracan species.