Phylogenetic Pattern and Developmental Process in Drosophila

Abstract

Recent molecular and morphological results on the phylogenetics of Drosophila and other Drosophilidae are reviewed. There is some consensus on the redefinition of Drosophila to make it a monophyletic group, except for the controversial placement of the Hawaiian Drosophila and the subgenus Sophophora. The possibility of Hawaiian Drosophila as a group that is morpho? logically atavistic (e.g., with many character reversals) is discussed. Drosophila development is reviewed, with focus on understanding the developmental genetic and molecular bases of char? acter convergence and reversal in drosophilid phylogenetics and its applications to homology decisions. The clustering of convergent characters on cladograms is discussed as a consequence of developmental constraints. The convergent evolution of broadened head shape in male dro- sophilids is presented as an example. Molecular and developmental analysis of homoplastic characters pivotal to phylogenetic schemes, such as eye setae in Drosophila sensu stricto and the Hawaiian species, can be of fundamental importance for homology assessment. (Drosophila; homeotic genes; homology assessment; systematics; molecular evolution.) The fruit fly Drosophila is well known for its importance in experimental and mech? anistic biology. In this article, we stress the impact that the study of Drosophila has had in revolutionizing many aspects of modern biology and how this bears on phyloge? netic reconstruction. Our central theme is