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Despite exhaustive investigation of present-day Nautilus, the phylogenetic relationships of the five or six recognized species within this genus remain unclear. Mitochondrial and nuclear DNA sequence data plus a suite of morphological characters are used to investigate phylogenetic relationships. Systematic analysis of the morphological variation fails to characterize described species as independent lineages. However, DNA sequence analysis indicates that there are three geographically distinct clades consisting of western Pacific, eastern Australian/Papua-New Guinean, and western Australian/Indonesian forms. The morphologically and genetically distinct species Nautilus scrobiculatus falls outside the three geographically recognized assemblages. Members of the genus Nautilus also exhibit low levels of sequence divergence. All these data suggest that Nautilus is currently undergoing diversification, which may have begun only several million years ago. These data also suggest that some of the morphological features used to define Nautilus species may simply represent fixed variations in isolated populations within the same species.

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Background: Mitochondria contain small genomes that are physically separate from those of nuclei. Their comparison serves as a model system for understanding the processes of genome evolution. Although complete mitochondrial genome sequences have been reported for more than 600 animals, the taxonomic sampling is highly biased toward vertebrates and arthropods, leaving much of the diversity yet uncharacterized.

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.

Based on a combination of molecular and morphological characters, two endemic Hawaiian genera, Titanochaeta Knab and Grimshawomyia Hardy, are transferred to subgenera within the genus Scaptomyza Hardy as is the Drosophila subgenus Engiscaptomyza Kaneshiro. Replacement names for three preoccupied species, Scaptomyza (Titanochaeta) neoevexa O’Grady et al., nom. nov. (for Titanochaeta evaza Hardy), S. (Titanochaeta) neokauaiensis O’Grady et al., nom. nov. (for Titanochaeta kauaiensis Hardy), and S. (Titanochaeta) neosilvicola O’Grady et al., nom. nov. (for Titanochaeta silvicola Hardy), are proposed. This brings the total number of described species in the genus Scaptomyza to 272, of which 141 are endemic to the Hawaiian Archipelago. In comparison, the genus Drosophila contains 368 species endemic to the Hawaiian Islands. Keys for the identification of the Hawaiian subgenera of Scaptomyza and species of Engiscaptomyza, Titanochaeta, and Grimshawomyia are also included.

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Our understanding of insect development and evolution has increased greatly due to recent advances in the comparative developmental approach. Modem 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 morphologicallandmarking. Exi~ng 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 be essentialto 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.