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

Pseudocordylus capensis, a melanistic lizard, is regarded as a basal specie s in the phylogeny of the family Cordylidae and is endemic to the Cape Fold Mountains. Data for this study were obtained from measurements and dissect ions of museum specimens (N = 68). Sexual maturity in both sexes is attaine d at around 80-90 mm snout-vent length (SVL). Body sizes (SVL) differed sig nificantly between sexes, the mean SVL of adult males being 92.3 mm (range 78.4-04.2) and that of adult females 95.9 mm (range 83.1-108.5). Although t he rate of increase in head measurements did not differ significantly betwe en sexes, analysis of covariance (ANCOVA) indicated that head dimensions ar e marginally, but significantly, larger in males than in females of equival ent 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 e nvironment. and to differential growth to increase female reproductive fitn ess, rather than to be the result of sexual selection. Males exhibit testic ular recrudescence during autumn, with full spermiogenesis during winter ma intained through spring (October). The testicular cycle shows characteristi cs of both 'post-nuptial' and 'pre-nuptial' cycles previously described in Cordylidae lizards. Small testicular volume, associated with testicular reg ression. was recorded during summer (November/December). Spermatozoa were p resent in the epididymis from May through to October. In synchrony with the spermatogenic cycle, the onset of vitellogenesis in females starts in autu mn. 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 cor responds to the autumn cycles reported for all other female Cordylidae liza rds studied to date, therefore pointing to strong conservatism regarding th e 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 sum mer months. The fact that this phylogenetically basal species exhibits well -synchronised male and female autumn gonadal cycles adds to the data that s uggest these reproductive traits evolved during the early divergence from t he Cordyliformes ancestor and that the evolution of viviparity may be linke d to this event or followed soon after.