Molecular Data Confirms the Species Status of the Christmas Island Hawk-Owl Ninox natalis

Abstract

DNA sequences from the mitochondrial ND2 gene were used to assess the taxonomic status of the Christmas Island Hawk-Owl Ninox natalis. Sequence variation was examined across 17 specimens representing 9 species and subspecies within the genus Ninox. The comparisons revealed a correlation between taxonomic level and genetic divergence with a clear separation between the levels of sequence divergence observed in comparisons involving individuals, subspecies and species. These observations provided strong endorsement for the use of DNA sequence data to assess the taxonomic status and phylogenetic relationships of N. natalis. Levels of sequence divergence recorded between the three forms of the N. squamipila complex examined (squamipila, hypogramma and natalis) ranged from 4.0% to 4.8%. These were comparable to the levels of divergence observed between obviously distinct species such as N. rufa and N. strenua (5.4%) and were consistently greater than observed among subspecies within the monophyletic N. novaeseelandiae complex (1.5% to 2.3% between novaesee-landiae, leucopsis and undulata). The genetic distinctiveness of all three forms of squamipila was also apparent from phylogenetic analysis of the data. Distance and parsimony methods both failed to identify any of the three forms of squamipila as forming a monophyletic assemblage. Based on the combined evidence (sequence divergence and phylogenetic position) it is concluded that squamipila, hypogramma and natalis each represent separate species in the genus Ninox. These findings have implications for conservation efforts in the region.