Seasonality in Ovarian Cycles among Tropical Anolis Lizards

Ovarian cycles were studied in six species of Anolis lizards from Puerto Rico. All are markedly seasonal, with egg production dropping in the autumn—winter months. Marked interspecific and intraspecific differences in onset, duration, and extent of cycling correlated with altitude. In general, upland populations decline earlier, more severely, and for a longer time than sea level populations. In most lowland populations some females are gravid throughout the year; among most upland populations there are usually one or two months when virtually no females are gravid. Rainfall has previously been implicated as the most important environmental variable to explain ovarian cycles of tropical lizards. Rainfall does not explain the patterns observed on Puerto Rico, but temperature or a combined photothermal effect does. Reconsideration of previously published data on ovarian cycles in tropical anoles strongly suggests that the initial decline is not because of changing rainfall patterns but is again a response to a thermal or photothermal cue.