No Sexual Size Dimorphism in the Frog Crinia georgiana (Anura: Myobatrachidae): An Examination of Pre- and Postmaturational Growth

Sexual differences in maximum adult size occur commonly in frogs. We examined pre- and postmaturational growth of male and female Crinia georgiana and showed that sexual size dimorphism (SSD) of adults does not occur in this species. An experimental investigation of prematurational growth demonstrated that males averaged larger at maturation than females but that the sexes did not differ in the range of sizes at maturity. All individuals reached maturity by 14 months of age regardless of body size or sex, suggesting an age threshold to maturity of approximately one year in this species. In addition, C. georgiana have an unusually wide range of adult body sizes compared to other species and sexual differences in adult body size distributions. Thus, the lack of SSD in this species occurs in spite of sexual differences in growth rates. We hypothesize that sexual selection may be one of several mechanisms behind the lack of SSD and unusual body size variation in this species.