GEOGRAPHIC-VARIATION IN GROWTH AND SEXUAL SIZE DIMORPHISM OF BOG TURTLES (CLEMMYS MUHLENBERGII)

We examined sexual size dimorphism (SSD) and growth rates in samples o f bog turtles (Clemmys muhlenbergii) from North Carolina, Pennsylvania and New Jersey. Mean carapace length (CL) of males was significantly greater than mean CL of females in all three states. However, the degr ee of SSD varied significantly among stales. Specimens from North Caro lina had the greatest SSD, the largest mean adult CL, and the largest mean hatchling CL. Growth rates were rapid until about age 6 and a CL of 80 mm. Males grew faster than females thereafter. A comparison of t he three parameters estimated from von Bertalanffy growth equations sh owed significant differences for asymptotes between sexes and states f or the North Carolina and Pennsylvania samples, but not for the growth rare constant (parameter k). Geographic variation in SSD appears to b e a result of differences in growth related to the timing of maturity and the approach to asymptotic body size caused by indeterminate growt h, or both. We suggest that male-biased SSD in this species is ultimat ely a consequence of the advantage conferred to larger males in male-m ale interactions and during mating.