Towards a natural classification of African toads (Anura, Bufonidae): Past progress and future prospects

Abstract

African bufonid toads (especially members of the genus Bufo) are a relatively uniform group morphologically, but beneath this apparent uniformity lies a higher level of diversity in habits and lifestyle than is initially evident. Members of the group exhibit considerable variation in size (from the very small Bufo beiranus to the very large Bufo mauritanicus), habitat preference and reproductive mode. The latter ranges from ‘normal’ oviparity with a large egg clutch and free living tadpole stage, through ovoviviparity to true viviparity with progressive reduction in egg clutch size. It might be expected that this diversity of form, ecological preference and reproductive capability would have been a stimulus to systematists to make bufonid toads one of the most intensively studied groups of African anurans. In fact, both our current state of knowledge of their phylogenetic relationships and our ability to discriminate species and genera remain poor. These deficiencies hamper progress in the study of all aspects of their biology, especially morphology, distribution, behaviour, ecology and biogeography. The present paper reviews the progress that has been made towards the goal of a natural or phylogenetic classification for the African Bufonidae, and includes suggestions on how this elusive aim may be attained within a reasonable period of time.