Convergence and vicariance: speciation of chameleons in the Cape Fold Mountains, South Africa, and the description of three new species of Bradypodion Fitzinger, 1843

Abstract

ABSTRACT The mechanisms that underpin ecological speciation, morphological convergence and the evolution of ecological morphotypes (ecomorphs) in squamates have allowed for a better appreciation of the speciation process in chameleons. In particular, attention has been drawn to several populations of chameleons (Sauria, Chamaeleonidae, Bradypodion) from the Cape Fold Mountains, South Africa. Previous work suggested that these populations are genetically divergent, but with strong similarities in phenotype. Using an integrative taxonomic approach that accounts for genetic diversity, habitat and morphology, three of these populations are described as species. One population is from an isolated forest patch and is genetically different at the species level, but morphologically similar to Bradypodion damaranum (Boulenger, 1887) from forested areas in the Knysna region. Although not sister species, the two are in the same clade and probably diverged through vicariance of the forest. Two other populations are from fynbos habitat in adjacent mountain ranges (Tsitsikamma/Langkloof/Kouga mountains and Baviaanskloof Mountains) and are also morphologically similar, but genetically divergent at the species level. These two species are not sister taxa and are not in the same clade yet have a virtually identical phenotype presumably as the result of convergent evolution for the fynbos habitat. Within the context of morphological taxonomy, these populations have been difficult to evaluate. However, when viewed in the context of ecological speciation, convergence and morphological conservatism, the species boundaries are apparent, allowing for them to be described as new taxa.