Growth, maturity, and reproduction of the wood turtle, Clemmys insculpta (Le Conte, 1830) in Virginia.

摘要

The wood turtle, Clemmys insculpta (Le Conte, 1830), is a cold adapted, semiaquatic species found in northeastern North America. Although variation in life history traits has been studied in several species of turtles, to date, there has been only one study on the wood turtle that attempted to test life history theory, and this study was conducted on a population at the northern limit of the range. The objectives of this study were to describe and quantify growth, maturity, sexual dimorphism, and reproduction in a northern Virginia population of wood turtles. Growth showed the typical chelonian pattern with rate inversely related to carapace length. In general, growth of both sexes was similar and fairly rapid until a carapace length of 160 mm was attained around nine years. Following maturity, growth in females appeared to slow more swiftly than that of males, although there was a good deal of variation in age-length relationships for both sexes. Approximately 80% of females nested in each year between 27 May and 26 June. Clutch size averaged 8.9 eggs. Eggs were generally ellipsoidal with a mean mass of 12.75g, a mean length of 37.9mm, and a mean width of 23.96mm. No evidence for optimal egg size theory was found when the effects of female body size were removed by partial correlation. Both relative clutch size and relative clutch mass were generally constant across body size. Selection for larger eggs appears to being a major factor behind variation in body size among wood turtles from northern Virginia. Evidently, selection on body size and age at maturity does not follow a latitudinal gradient because female wood turtles along the northern edge of the distribution mature later at larger sizes, but elsewhere these traits were highly variable. In addition, no clear clinal pattern emerged when comparisons of mean egg mass were made among five populations. Investigation of geographic variation in wood turtle life history traits would benefit from a larger sample of populations and the incorporation of additional climatic parameters.