Evidence for continuous iteroparity in a temperate-zone frog, the red-crowned toadlet, Pseudophryne australis (Anura : Myobatrachidae)

Abstract

The breeding behaviour of the red-crowned toadlet, Pseudophryne australis, was observed both in the field and in captivity. Female and male red-crowned toadlets were active in the field throughout the year. New egg masses were observed all year except mid-winter. Females returned in a gravid condition repeatedly to the breeding site over years and presumably deposited eggs, and a captive female has laid 34 clutches over 7.25 years. P. australis has evolved continuous iteroparity in a region where most frogs breed once a year, seasonally, in reliable long-lasting ponds or permanent creeks. We suggest that the comparatively extreme iteroparity observed is a result of the limitations imposed on the species in the choice of oviposition time, due to unpredictable rainfall, and of the limited availability and suitability of nesting sites.

Further, iteroparity may have evolved because there is high variance in reproductive success, or particularly high recruitment losses incurred as a result of the desiccation of embryos or larvae in the ephemeral breeding sites. The adaptive response is to lay small clutches often and to gamble that follow up rains will occur on some occasions to enable recruitment. The alternative, to lay a large clutch of eggs at one time and have the ephemeral pond dry because there was no follow-up rain, would lead to total reproductive loss.