Implications of phylogeography and population genetics for subspecies taxonomy of Grey (Pacific Black) Duck Anas superciliosa and its conservation in New Zealand

Abstract

Subspecies delineations may not reflect actual intraspecific diversity; an issue that becomes important when conservation of populations and/or subspecies that face severe declines is involved. The Grey Duck in New Zealand is considered a separate subspecies Anas superciliosa superciliosa from the Pacific Black Duck A. s. rogersi of Australia, even though poorly differentiated morphologically. Because the New Zealand and Australian populations of A. superciliosa are considered taxonomically distinct, the decline of New Zealand's Grey Duck and its hybridization with the introduced Mallard A. platyrhynchos has led to assignment of "endangered" conservation status. Taxonomic distinction and absence of periodic gene flow between the Australian and New Zealand populations are crucial for acceptance of this status. We used phylogeographic analysis of mitochondrial DNA control region sequences to determine whether haplotypes representing current subspecies are unique or are more consistent with populations in the two countries being considered the same subspecies. Two highly divergent genetic lineages of Grey Duck occur in New Zealand. One lineage (Group I) is found only in New Zealand primarily on North Island, while the other (Group II), occurs in populations throughout New Zealand and Australia. The split between Group I and II lineages is on the order of that found between some avian species. Even though subspecific designations of A. s. superciliosa and A. s. rogersi do not hold up based on molecular data, we identify a need for Grey Duck in New Zealand to be conserved to maintain the historical diversity within the species.