This paper summarises evidence for low rates of annual reproductive output (no. of offspring or eggs/female/yr) in New Zealand reptiles. Tuatara (Sphenodon spp.) and the geckos Hoplodactylus maculatus and H. duvaucelii are cold-adapted, nocturnal, and long-lived, with evidence in at least some populations of less-than-annual reproduction. Annual reproductive output estimated for three tuatara populations ranges from 1.27 to 2.28 eggs/ female/yr. New Zealand geckos produce 2 offspring/female/yr. Hoplodactylus maculatus in the Macraes-Middlemarch region of Central Otago produces only about 0.85 offspring/female/yr, as a consequence of biennial reproduction and clutch sizes that are often less than two. The diurnal skinks Leiolopisma grande and L. otagense from the same region breed annually and have larger clutch sizes, so their annual reproductive output is higher (2.17 and 2.34 offspring/female/yr, respectively). Other wild populations of New Zealand skinks typically produce 1-5 offspring/female/yr. Unlike many species of oviparous geckos overseas, the viviparous New Zealand geckos do not produce multiple clutches per year, and this contributes to relatively low annual reproductive output in some species. Viviparous New Zealand skinks have similar annual reproductive output to viviparous skinks of similar body size from other parts of the world. Low annual reproductive output in New Zealand lizards thus appears to reflect, in part, responses to cool summer temperatures in association with a viviparous reproductive mode (geckos), as well as phylogenetic effects (colonisation by lineages of small clutch and body size, in geckos and skinks).
Cycles in gonadal activity and plasma sex steroid concentrations were investigated in wild female and male tuatara on Stephens Island, New Zealand. Females nest once every four years on average. Vitellogenesis is spread over the first three years, and mating, ovulation and nesting occur in the fourth. Oviducal eggs are carried for6–8 months before nesting. Although the length of this ovarian cycle is unparalleled among oviparous reptiles, the associated cycles in plasma concentrations of sex steroids are similar to those in other reptiles. Mean plasma concentrations of oestradiol increase during vitellogenesis, peak at mating, fall rapidly before or around ovulation, are low during most of gravidity, and rise slightly during late gravidity‐nesting. Plasma concentrations of testosterone show a similarcycle. Mean plasma concentrations of progesterone are low during vitellogenesis and peak around ovulation. This periovulatory surge falls within1–2 months, and mean concentrations are low during the final 5–6 months of gravidity. Male tuatara show an annual, pre‐nuptial reproductive cycle. Mean plasma concentrations of testosterone are low during winter, rise during spring, peak during midsummer‐early autumn, when pre‐nuptial displays and mating occur, and fall in mid autumn. Limited histological data indicate that spermiogenesis occurs during midsummer‐early autumn, and also support a previous study suggesting that there may be no period of complete testicular and epididymal regression. In comparison with the pre‐nuptial cycles of other temperate‐zone reptiles, the cycle in male tuatara shows a more prolonged duration of testicular activity and of rising or elevated plasma testosterone concentrations. The prolonged reproductive cycles of male and female tuatara may be adaptations to a temperate environment with cool summers and cool, but not freezing, winters.
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