Life-History Variation in Marine Turtles

We studied correlations among traits related to body size and reproductive behavior in marine turtles, using data from 96 different populations representing seven species. Our analyses focused on patterns of phenotypic covariation among species and among populations within species. At the species level, body size correlated positively with several reproductive traits, including egg size and overall reproductive effort. A trade-off between clutch size and egg size was confirmed for marine turtles, after factoring out the effects of body size. Patterns of variation within species were different from those among species. For example, in five out of six species there was a positive relationship between adult body size and clutch size, although this correlation was not found at the interspecific level. We also found important differences among species in the way life-history traits correlated with one another. Four species having a sufficient number of samples exhibited congruent worldwide patterns of body size variation. A comparative approach may prove useful for extending demographic models developed for loggerhead turtles to less well-known species, even though many of the model parameters have not been estimated for other species.