Reconstructing paternal genotypes to infer patterns of sperm storage and sexual selection in the hawksbill turtle

Abstract

Postcopulatory sperm storage can serve a range of functions, including ensuring fertility, allowing delayed fertilization and facilitating sexual selection. Sperm storage is likely to be particularly important in wide-ranging animals with low population densities, but its prevalence and importance in such taxa, and its role in promoting sexual selection, are poorly known. Here, we use a powerful microsatellite array and paternal genotype reconstruction to assess the prevalence of sperm storage and test sexual selection hypotheses of genetic biases to paternity in one such species, the critically endangered hawksbill turtle, Eretmochelys imbricata. In the majority of females (90.7%, N = 43), all offspring were sired by a single male. In the few cases of multiple paternity (9.3%), two males fertilized each female. Importantly, the identity and proportional fertilization success of males were consistent across all sequential nests laid by individual females over the breeding season (up to five nests over 75 days). No males were identified as having fertilized more than one female, suggesting that a large number of males are available to females. No evidence for biases to paternity based on heterozygosity or relatedness was found. These results indicate that female hawksbill turtles are predominantly monogamous within a season, store sperm for the duration of the nesting season and do not re-mate between nests. Furthermore, females do not appear to be using sperm storage to facilitate sexual selection. Consequently, the primary value of storing sperm in marine turtles may be to uncouple mating and fertilization in time and avoid costly re-mating.

Female reproductive qualities affect male painted turtle (Chrysemys picta marginata) reproductive success

“…3). Similar frequencies of repeat paternity have been reported in other populations of painted turtles (100 % within season and 40 % among years, Pearse et al 2002) and in other species of freshwater (58 % among years, Roques et al 2006) and sea turtles (near 100 % within season, Fitzsimmons 1998;Phillips et al 2013).…”

Evaluating the importance of Marine Protected Areas for the conservation of hawksbill turtles Eretmochelys imbricata nesting in the Dominican Republic

“…obs.). Despite the evident importance of this area for biodiversity conservation, and its protected status, it is threatened by the extraction of sand for commercial purposes and illegal construction by the hotel industry, as well as indiscriminate fishing activities (Perdomo et al 2010). Such lack of enforcement of conservation actions in protected areas hinders the effective protection of these critical habitats for marine turtles and is an urgent target for improved conservation.…”

Advances in the Application of Genetics in Marine Turtle Biology and Conservation

“…Multiple paternity has been detected in hawksbills (Phillips et al, 2013), loggerheads (Sari et al, 2017), leatherbacks (Stewart and Dutton, 2011), olive ridleys (Jensen et al, 2006), and green turtles (FitzSimmons, 1998), and the number of studies in this area is increasing. By tracking male identities over several nesting seasons, male remigration/breeding intervals may also be determined by recording how often a known male is detected in hatchling genetic signatures.…”

“…To date, from the studies that looked at this ratio specifically, there does not appear to be a reduction in the proportion of males in breeding populations, despite there being female biases in the hatchling sex ratios. For example, Wright et al (2012b) found 1.4 males for every female in a green turtle population, Dutton (2011, 2014) found 1.4 males and 1 male (respectively) for every female in leatherback turtles, and Phillips et al (2013) found 1.1 males for every female in a hawksbill population. In all of these studies, there were more males than females detected within the breeding population within a single year.…”