SSD in marine turtles
Availability of body sizes for both sexes within a single population
varied widely among the seven species of marine turtles (Supplementary
Table S2). By far the most data were available for the green turtle
(Chelonia mydas ), which yielded credible estimates from 18
studies (Fig. 1A), with six populations for the loggerhead
(Caretta caretta ), four populations for the olive ridley
(Lepidochelys olivacea ), three populations for the hawksbill
(Eretmochelys imbricata ), two populations for the leatherback
(Dermochelys coriacea ), and two studies for the Kemp’s ridley
(Lepidochelys kempii ), and a single population of the flatback
(Natator depressus ). The sex-specific means and samples sizes are
shown in Figure 1B and summarised in Supplementary Table S2. For the
species for which we have estimates from five or more populations
(C. mydas , C. caretta ), it is noteworthy that the degree
and direction of SSD varies.
Figure 1A also illustrates the regression of sex-specific mean values
(male vs female) for all populations. Neither the slope nor the
intercept of this regression differed significantly from the null
expectation (slope: t(33)=0.052, tcrit=2.034, p=1;
intercept: t(33)=-0.514, tcrit=2.034, p=0.611). The
upper 95% confidence interval of the regression is slightly below the
1:1 line, indicating a weak female-biased SSD. Examination of the
scatter suggests that this overall pattern is driven largely by C.
mydas .