Taxonomic status of the Namibian Violet Woodhoopoe Phoeniculus damarensis as determined by mitochondrial DNA

The Violet Woodhoopoe Phoeniculus damarensis damarensis is considered a threatened subspecies and one of ten bird taxa endemic to Namibia and southwestern Angola. This species is distinguished from the more common and widespread Green Woodhoopoe P. purpureus by a variable plumage trait, resulting in uncertainty as to the distribution and degree of overlap between these taxa. Mitochondrial sequences from the cytochrome oxidase I (COI) gene show minimal divergence among Namibian woodhoopoes (0.15%, including P. d. damarensis and R p. angolensis), and low divergence between Namibian birds and South African (1.06%, R p. purpureus) or Kenyan (2.30%, P. p. marwitzi) Green Woodhoopoes. Sequences from Namibian woodhoopoes are phylogenetically nested within R purpureus, rendering this species paraphyletic at mitochondrial DNA. Genetic divergences among Violet and Green Woodhoopoes fall within the range of intraspecific values recorded for avian mitochondrial protein coding genes, and are substantially less than most interspecific values. Comparisons with the related Scimitarbill Rhinopomastus cyanomelas suggest that the low divergences among Green and Violet Woodhoopoes are not an artefact of slow evolutionary rates in Phoeniculidae. We suggest that in the absence of evidence for evolutionary independence or a clear phenotypic diagnosis, the Violet Woodhoopoe should be synonymized with the Green Woodhoopoe. It is the status of this taxon that should be considered in formulating priorities for avian conservation in Namibia.