Species delimitation: new approaches for discovering diversity.

Systematics can be considered to have two major goals: (1) to discover and describe species and (2) to determine the phylogenetic relationships of these species. But even a quick perusal of titles in Systematic Biology throughout most of its 15-year history will confirm an obvious fact: most articles focus on reconstructing phylogenies and on using these phylogenies to address evolutionary or biogeographic questions, with few papers on the methodology underlying this first major goal of systematics research (Fig. 1). Nevertheless, species delimitation, the process by which species boundaries are determined and new species are discovered, may finally be emerging as a major topic in modern systematics (e.g., Sites and Marshall, 2003). New methods for species delimitation are being developed (e.g., Puorto et al., 2001; Templeton, 2001; Wiens and Penkrot, 2002; Morando et al., 2003; Pons et al., 2006) and compared (e.g., Marshall et al., 2006; Pons et al., 2006). Ambitious proposals have been made, with the goal of accelerating the rate at which new species are discovered and described, including DNA barcoding (e.g., Hebert et al., 2003, 2004), DNA taxonomy (Tautz et al., 2003), and Web-based taxonomy (e.g., Godfray, 2002; Scoble, 2004; Knapp et al., 2007). Controversies are raging in the literature over these proposals (especially over DNA barcoding: Will et al., 2005; Brower, 2006; Hickerson et al., 2006; Meier et al., 2006) and other aspects of species delimitation and over the consequences of new approaches in species delimitation for other fields, such as ecology and conservation (Agapow et al., 2004; Isaac et al., 2004; Padial and de la Riva, 2006). This new emphasis on species delimitation has arisen (at least in part) because of growing concern over threats to biodiversity and the desire to describe as many species as possible as quickly and accurately as possible before they disappear. However, an increased interest in species delimitation is barely reflected in the pages of Systematic Biology, if at all (Fig. 1). This disconnect was my major motivation for organizing a symposium for the Society of Systematic Biologists on this topic.