POPULATION-STRUCTURE AND THE EVOLUTION OF SEXUAL SIZE DIMORPHISM AND SEX-RATIOS IN AN INSULAR POPULATION OF FLORIDA BOX TURTLES (TERRAPENE CAROLINA BAURI)

Hypotheses in the chelonian literature suggest that in species with se xual size dimorphism, the smaller sex will mature at a smaller size an d a younger age than the larger sex, sex ratios should be biased in fa vor of the earlier maturing sex, and deviations from a 1:1 sex ratio r esult from maturation of the smaller sex at a younger age. I tested th ese hypotheses using data collected from 1991 to 1995 on an insular (E gmont Key) population of Florida box turtles, Terrapene carolina bauri . Contrary to predictions, the earlier maturing sex (males) grew to la rger sizes than the late maturing sex. Males were significantly larger than females in mean carapace length but not mean body mass. Sex rati os were not balanced, favoring the earlier maturing sex (1.6 males: 1 female), but the sex-ratio imbalance did not result from faster matura tion of the smaller sex. The imbalance in the sex ratio in Egmont Key' s box turtles is not the result of sampling biases; it may result from nest placement. Size-class structure and sex ratios can provide valua ble insights into the status and trends of populations of long-lived t urtles.