Biological systematics encompasses three distinct activities: taxonomy, classification (which may or may not be a reasonable reflection of phylogeny) and nomenclature (Fig. 1). Although systematists rigorously and distinctly practice these three components, they are often amalgamated under the term “taxonomy.” While the breadth of “taxonomy” is clearly understood among most practitioners, it ca...

Red algal systematics has a solid morphological foundation, based on analyses of female reproductive structures and post-fertilization development by Kylin and other workers. Recognition of the value of pit-plug ultrastructure was a catalyst leading to refinement of the Kylinian ordinal classification. Molecular approaches to systematics have further advanced our understanding of the red algae ...

The fossil record and systematics of murid rodents, reservoirs of zoonotic cutaneous leishmaniasis in the Palaearctic, Oriental, African, Nearctic and Neotropical, strongly support a Palaearctic origin of Leishmania. The fossil record and systematics of phlebotomine sand flies reinforce this idea. Interpretations of molecular data that place the origin of Leishmania in the Neotropical are incon...

Freshwater crayfish have served as model organisms for over 125 years in scientific research, from areas such as neurobiology and vision research to conservation biology and evolution. Recently, evolutionary histories in the form of phylogenies have served as a critical foundation for testing hypotheses in such diverse research areas as well. In this article, I review the amazing diversity of f...

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 systemat...

Morphological features of the Acoela appear to be quite plastic, including those of the copulatory organs, which provide the principle characteristics used for the systematics of this group. Consequently, classification schemes of the Acoela comprise numerous polyphyletic groupings. In this review, we detail recent revisions of acoel systematics using molecular sequence data and new and reevalu...

Sipunculans (also known as peanut worms) are an ancient group of exclusively marine worms with a global distribution and a fossil record that dates back to the Early Cambrian. The systematics of sipunculans, now considered a distinct subclade of Annelida, has been studied for decades using morphological and molecular characters, and has reached the limits of Sanger-based approaches. Here, we re...

Modern morphology-based systematics, including questions of incongruence with molecular data, emphasizes analysis over similarity criteria to assess homology. Yet detailed examination of a few key characters, using new tools and processes such as computerized, three-dimensional ultrastructural reconstruction of cell complexes, can resolve apparent incongruence by re-examining primary homologies...

The time is past when a research program in systematics should be based on only a few genes, extant taxa, and ultrametric trees. Cheap genome sequencing, powerful statistical methods, and new fossil discoveries promise to reinvigorate research programs in evolutionary biology. Population genetics, phylogeography, and species delimitation all benefit from genomic data, not just tree building alo...