Relationships of the South African lizards assigned toAporosaura, MerolesandPedioplanis(Reptilia: Lacertidae)

Abstract

Phylogenetic analyses, using parsimony and compatibility methods, were carried out on the South African lacertid lizards assigned in recent times to Aporosaura, Meroles and Pedioplanis. These were based on 80 primary and 102 binary morphological characters which were drawn from osteology, external features, muscles, kidneys and reproductive systems. Contrary to some previous interpretations, there are two well-defined clades: Meroles plus Aporosaura, and Pedioplanis; these form successive branches on the main stem of the phylogeny of advanced lacertids. The clades show considerable parallel development of derived features, presumably because they had very similar initial genetic potential. Relationships within the two groups are shown on p. 800 and p. 802. As Aporosaura anchietae is sister taxon to a clade consisting of three of the seven species of Meroles, it has been transferred to that genus. Relationships in Meroles-Aporosaura are very well substantiated, in contrast to the situation in Pedioplanis. This difference appears to be related to the different kinds of evolutionary history that the two groups have had. The Meroles-Aporosaura clade has spread progressively into increasingly stringent and singular aeolian sand environments which have elicited the production of many, often unique, derived character states related to the functional problems of survival in such situations. As these states are rarely duplicated in outgroups, the characters concerned are easily polarized. This, together with their abundance, means that a robust basis for phylogenetic inference is available. In contrast, Pedioplanis exhibits relatively limited ecological radiation of a kind that also occurs in related groups, and the functionally related derived states elicited are fewer and less distinctive. In fact, production of a phylogeny for Pedioplanis is very dependent on genital characters which seem to be substantially independent of the main ecological changes that have occurred in the genus. The premaxilla is embraced dorsally by the anterior processes of the maxillae in most lacertids, but the processes are less extensive in two sister species of Pedioplanis, P. burchelli and P. laticeps. This modified condition also occurs in the genera Eremias, Acanthodactylus, Mesalina and Ophisops, which together constitute a clade that forms the sister group of Pedioplanis. The modification provides extra evidence for the holophyly of the clade, even though presence in some Pedioplanis shows it to be homoplasious.