PS 80-205
Estimates of mating structure and operational sex ratios in South African loggerhead turtles using kinship approaches based on microsatellite markers
Estimates of population viability for conservation are often based on population specific parameters such as population size, sex ratios and rates of recruitment. Such estimates are difficult to derive in marine turtles, because they are long-lived, little is known about cohort sizes once hatchlings leave their nesting sites, and only adult females return to nursery grounds. In addition, temperature-dependent sex determination affects sex ratios. Understanding the ratio of breeding males to females is important because it can affect the ability of a population to persist. The loggerhead turtle (Caretta caretta) is an endangered sea turtle with nesting sites distributed worldwide. The South African population is at the southernmost distribution of the species range, but little is known about the mating system or the sex ratio in this population. We collected tissue samples in iSimangaliso Wetland Park, South Africa, of 1522 hatchlings from 55 nests and 155 females during the 2009-2010 breeding season and used 16 microsatellite loci (short tandem repeating sequences) to determine whether the population exhibited polyandry or polygamy and to estimate operational sex ratios. Estimates were based on kinship estimates between offspring within each nest
Results/Conclusions
Using COLONY, we reconstructed sibling relationships and parental genotypes. Based on comparisons with the known females sampled, we detected 22 mothers and 29 fathers. We found evidence of sperm storage and polyandry in the 22 nests we analyzed. The operational sex ratio was found to be 1 female to 1.32 males. Using LDNe we estimated the effective population size to be in the range of 245.9-326.7 individuals. The results of this study will be used in devising management plans for loggerhead turtle conservation, and will be a valuable time point in understanding the South African population once samples from more recent breeding seasons have been analyzed.