The evolutionary history of a species or a group of related species is known as a phylogeny. Attempts to reconstruct phylogenetic history fall within the realm of systematics, or the study of biological diversity (Campbell, 1993). The diversity we observe today has arisen through evolutionary processes that result in the formation of new species and the extinction of others. By classifying living organisms into similar and hierarchical groups such as species and genera, we hope to observe the relationships that exist among groups and how evolutionary processes may be driving the incredible biodiversity on Earth. Taxonomy is the identification and classification of species and lies at the heart of systematics. As we shall see, the criteria used to establish taxonomic boundaries are of primary importance, and conflict often is created between classification schemes developed using different criteria.

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