Generation glands and sexual size dimorphism in the Cape Crag Lizard, Pseudocordylus microlepidotus

Abstract

The Cape Crag Lizard, Pseudocordylus microlepidotus, is unique among cordylid lizards in that generation glands are not restricted to the femoral region, but also occur on the dorsum and in the inguinal region. We analysed 274 museum specimens of P. microlepidotus, collected at various localities in the Western Cape Province, South Africa, and found that generation glands ontogenetically first differentiate in the femoral region, then on the back along the vertebral line, and finally, in males only, in the inguinal region. In both sexes, generation glands start to differentiate before sexual maturity is reached, but males develop significantly more glands than females. Males have larger heads than females, but the sexes do not differ significantly in overall body size. High scar frequencies were recorded for both sexes and the sex ratio for the total sample was close to 1:1. The functional significance of the additional generation glands is discussed in context of the social structure of the species as inferred from the degree and direction of sexual size dimorphism and scar frequency data. Sexual size dimorphism recorded for P. microlepidotus is of a similar nature as that recorded for other cordylids occurring at high altitudes in the winter rainfall area of South Africa.