Phylogenetics and speciation of African Bradypterus and the Apalis thoracica complex

Abstract

Presented in this thesis is the mitochondrial DNA (mtDNA) cytochrome b gene analysis of the phylogenetic relationships within the Apalis thoracica complex (600bp) as well as among selected African Bradypterus species (603bp). Within A. thoracica 28 individuals from 20 subspecies were analysed. There was only molecular support for 13 historically isolated clades as opposed to the 21 subspecies recognized based on morphology. Among these molecularly defmed clades were clades lynesi, juscigularis and flavigularis, all three of which are of conservation concern and were previously treated as species by some based on their distinct morphology. Molecular clock dating estimated the clades to be of Pliocene age, whereas genetic differentiation within clades was of Plio-Pleistocene to Pleistocene age. This result is consistent with that of other African montane birds. Under the phylogenetic species concept all 11 clades could be recognised as species although a multifaceted approach to species recognition which will include vocalisation data is suggested. Contrary to expectation, the isolated East African clades did not exhibit more variation than the continuously distributed clades within southern Africa. In fact, significant phylogeographic breaks were identified within South Africa that need further investigation. For the African Bradypterus, 13 individuals from six of the 10 African species were analysed. These species were not monophyletic. Based on sequence divergence B. victorini was as different from the other members of the genus as it was from the out groups. In addition its song is very distinct and both males and females sing. Therefore, based on the molecular results presented in this thesis as well as vocalisation data and, it is proposed that B. victorini is not a Bradypterus. This result is particularly significant in light of the growing evidence that the Cape region acted as a repository for ancient animal taxa and holds implications for the conservation status of the region. The molecular data supported the classification of the taxa based on habitat and song but in addition clarified the placement of B. victorini and B. sylvaticus. The basal position of the latter among the remaining members of the genus indicates that Bradypterus is primarily a forest taxon that radiated into other habitats. It must however be kept in mind that the current dataset is based on six of the 10 African Bradypterus and none of the Asian species. The possibility of hybridisation between B. sylvaticus and B. barratti was raised and needs to be tested through additional sampling.