Ecology and environmental history, not just genetic diversity, brings important perspectives to defining species diversity — illustrated by moas

Abstract

We examine whether mitochondrial DNA (mtDNA) data can be used by itself to identify species limits in the extinct New Zealand moa, an order of birds that for the past 150 years has been difficult to classify. We argue that generally it cannot, and that a range of historical population parameters need to be considered when interpreting genetic and morphological diversity. We use the moas Emeus, Dinornis and Megalapteryx (Aves: Dinornithiformes) as examples. These taxa had very divergent palaeoecological preferences, and their ranges were affected quite differently during the glacial - interglacial cycles of the Pleistocene. We show that mtDNA diversity and genetic distances within and between these moa species is directly related to predicted population sizes over the preceding glacial period, and the likely geological longevity of populations in different areas. The interaction of these factors has produced a wide range of intraspecific diversity within moa genera, which illustrates why a simple quantitative cutoff value for genetic distance cannot be used to define species limits in moa (and potentially other taxa)