Crossroads, milestones and landmarks in insect development and evolution: implications for systematics

Our understanding of insect development and evolution has increased greatly due to recent advances in the comparative developmental approach. Modern developmental biology techniques such as in situ hybridization and molecular analysis of developmentally important genes and gene families have greatly facilitated these advances. The role of the comparative developmental approach in insect systematics is explored in this paper and we suggest two important applications of the approach to insect systematics--character dissection and morphological landmarking. Existing morphological characters can be dissected into their genetic and molecular components in some cases and this will lead to more and richer character information in systematic studies. Character landmarking will he essential to systematic studies for clarifying structures such as shapes or convergences, which are previously hard to analyze anatomical regions. Both approaches will aid greatly in expanding our understanding of homology in particular, and insect development in general.

The evolution and development of dipteran wing veins: a systematic approach

In this review, we use the wing veins of dipteran insects as potential models for understanding the evolution of development. We briefly discuss previous work in this field and examine the genetic complexity of wing formation, discussing the genes involved in wing formation and their roles in Drosophila wing development and vein formation. Furthermore, patterns of wing vein formation, addition, and reduction are discussed as they occur throughout the Diptera. Using the phyletic phenocopy paradigm, we draw attention to many wing vein morphologies that phenocopy various wing mutants in Drosophila melanogaster. The systematic issues of the nature of characters, homology, and the role of modern developmental approaches to evolutionary studies, which has recently become important, can be addressed from the perspective of the wing. We argue that further developmental evolutionary studies, and the interpretation of data therefrom, must be conducted within the context of a well-supported phylogeny of the organisms under study.

Character congruence of multiple data partitions and the origin of the Hawaiian Drosophilidae

We address two systematic questions, the origin and monophyly of the Hawaiian Drosophilidae and the question of how to analyze multiple data partitions containing disparate kinds of information, in this study. New evidence, from analysis of characters from morphology, mitochondrial DNA, and nuclear DNA suggests that the Hawaiian Drosophilidae are a monophyletic assemblage. Although we are not able to suggest a single species group which may represent the continental sister taxon to the Hawaiian Drosophilidae, the candidates suggested by our analysis, the melanicarobusta lineage and the virilis-repleta lineage, have been suggested by other investigators as probable sister taxa. Through analyses of our data partitions separately and in a variety of combinations, we conclude that the best phylogenetic hypothesis to be generated from multiple data partitions will be obtained if the data from these partitions are combined and analyzed simultaneously. We advocate performing tests for congruence between and among data partitions not to justify keeping them apart, but for understanding the interactions among the signals included in the analysis and how they affect the topology of, and support for, the total evidence tree.