Integrative taxonomy of birds : Studies into the nature, origin and delimitation of species

Abstract: Species are the basic currency in biodiversity studies but what constitutes a species has long been controversial. A major breakthough was the insight that most systematists agree that species are segments of population lineages, and that multiple lines of evidence should be employed and integrated, a procedure called integrative taxonomy. For this dissertation, I have studied integrative taxonomy from three angles. First, I address a series of influential claims about the nature and empirical basis of taxonomic change in birds. In Paper I, I show that taxonomic change is overwhelmingly data-driven. Thus, increasing numbers of species represent progress, not taxonomic inflation resulting from a change in species concept. In Paper II, I provide the first detailed quantitative analysis of how species are delimited in practice. This study shows that, contrary to widely held beliefs, avian taxonomy has not been dominated by the Biological Species Concept. Instead, species delimitation is increasingly pluralistic and eclectic. I argue that taxonomic practice is more unified than is implied by the controversy over species concepts. Integrative taxonomy can provide new insights into the speciation process. In Paper III, I show that two very different evolutionary patterns have been referred to by the term ‘ring species’ which are best distinguished using an integrative approach. Finally, two case studies of integrative taxonomy are presented. In Paper IV, we describe a new cryptic species of owl, the Rinjani Scops Owl (Otus jolandae), using evidence from plumage details, morphometrics, vocalizations and playback studies. Paper V presents a study of the evolutionary history of diversification in a widespread Indo-Pacific passerine, the Red-bellied Pitta (Erythropitta erythrogaster). Using molecular species delimitation methods and evidence from plumage details and morphometrics, we suggest that this species includes up to 17 species which originated during the Pleistocene