Reproduction and sexual dimorphism in the montane viviparous lizard,Pseudocordylus capensis(Sauria: Cordylidae)

Abstract

Pseudocordylus capensis , a melanistic lizard, is regarded as a basal species in the phylogeny of the family Cordylidae and is endemic to the Cape Fold Mountains. Data for this study were obtained from measurements and dissections of museum specimens ( N = 68). Sexual maturity in both sexes is attained at around 80-90 mm snout-vent length (SVL). Body sizes (SVL) differed significantly between sexes, the mean SVL of adult males being 92.3 mm (range 78.4−104.2) and that of adult females 95.9 mm (range 83.1-108.5). Although the rate of increase in head measurements did not differ significantly between sexes, analysis of covariance (ancova) indicated that head dimensions are marginally, but significantly, larger in males than in females of equivalent SVL. The slight female-plus dimorphism in SVL and male-plus dimorphism in head dimensions is suggested to be related to life in the cold montane environment, and to differential growth to increase female reproductive fitness, rather than to be the result of sexual selection. Males exhibit testicular recrudescence during autumn, with full spermiogenesis during winter maintained through spring (October). The testicular cycle shows characteristics of both ‘post-nuptial’ and ‘pre-nuptial’ cycles previously described in Cordylidae lizards. Small testicular volume, associated with testicular regression, was recorded during summer (November/December). Spermatozoa were present in the epididymis from May through to October. In synchrony with the spermatogenic cycle, the onset of vitellogenesis in females starts in autumn, culminating in ovulation during spring (September-October). Females are gravid during summer and give birth to 2-3 young in late summer (December-January). The timing of events during the reproductive cycle of females corresponds to the autumn cycles reported for all other female Cordylidae lizards studied to date, therefore pointing to strong conservatism regarding the timing of female reproductive cycles in this lizard family. Fatbody size in individuals of both sexes is largest during late summer and autumn, and progressively declines during winter to reach smallest sizes during the summer months. The fact that this phylogenetically basal species exhibits well-synchronised male and female autumn gonadal cycles adds to the data that suggest these reproductive traits evolved during the early divergence from the Cordyliformes ancestor and that the evolution of viviparity may be linked to this event or followed soon after.