Age, Size, and Growth of the Chilean Frog Pleurodema thaul (Anura: Leiuperidae): Latitudinal and Altitudinal Effects

Abstract

Age, longevity, size, and the effects of climate on growth and age at sexual maturity were analyzed in four populations of Pleurodema thaul (Leiuperidae) from Chile by comparing two populations at different latitudes but similar altitude (Limarí and Chaitén), and two populations at similar latitude but different altitudes (Itata and Laja). Body size was measured and age was estimated by skeletochronology applied to phalanges. In each population there was a positive relationship between body size and age, and growth decreased gradually after maturity. The longevity was estimated to be five years for females and males; age structures were similar between sexes. Pleurodema thaul showed intra-population variation in the degree of sexual dimorphism in growth patterns, age at sexual maturity, and size. Females were larger than males in the low altitude and latitude populations (Limarí and Itata), but did not differ significantly at high altitude and latitude populations (Chaitén and Laja). In all populations, sexual maturity was reached at two years of age by both sexes except that some females at high altitude and latitude did not mature until three years of age. The growth coefficient, according to von Bertalanffy's model, was greater in females than in males from Chaitén, greater in males from Limarí, and was similar between sexes in Itata and Laja. Pleurodema thaul populations from high latitude and altitude showed slower growth than populations from low latitude and altitude, but individuals achieved larger body size. The mean annual growth rate was greater in populations located at high altitude or latitude for males and females. These results allow inference of the responses of amphibians to changes in the environment, which is key for generating conservation strategies.