Paternal genotype reconstruction reveals multiple paternity and sex ratios in a breeding population of leatherback turtles (Dermochelys coriacea)

Abstract

When animals are difficult to observe while breeding, insights into the mating system may be gained by using molecular techniques. Patterns of extra-pair copulation, multiple paternity and parental genotype analysis may elucidate population characteristics that help improve knowledge of life history while informing management decisions. During the course of a long-term study of leatherback turtles, we assessed the level of multiple paternity in successive clutches for 12 known females nesting at Sandy Point National Wildlife Refuge (St. Croix, U.S. Virgin Islands). We used seven polymorphic microsatellite markers to genotype the females and 1,019 hatchlings representing 38 nests (3-4 clutches from each female). Using deductive genotype reconstruction and GERUD1.0, we identified the 12 mothers and 17 different fathers that were responsible for 38 nests. We found that seven females (58.3%) showed no evidence of multiple paternity in their clutches, while five females (41.7%) had mated with two males each. There was evidence of two fathers (polyandry) in successive clutches for these five females. Multiple fathers didn't contribute to clutches equally. For clutches laid by an individual female, the primary father was responsible for 53.7 to 85.9% of the hatchlings. We demonstrate the feasibility of using male genotype reconstruction to characterize the male component of this breeding population and to assess operational sex ratios for breeding sea turtles.

Pre-nesting Movements of Leatherback Sea Turtles, Dermochelys coriacea, in the Western Atlantic

“…However, knowledge gaps in the life history of this species remain, including understanding of female pre-nesting and mating behavior. Consistent paternity documented across successive nests suggests that sperm storage occurs from mating event(s) prior to the nesting season (Crim et al, 2002;Stewart and Dutton, 2011;Figgener et al, 2016) and that mating during inter-nesting periods may be rare. Therefore, as mature male and female turtles presumably aggregate to breed in specific areas, identifying where pre-nesting season mating opportunities occur may offer conservation value to the Atlantic leatherback population.…”

“…While all species of sea turtle exhibit polyandry (Kichler et al, 1999;Ireland et al, 2003;Jensen et al, 2006;Zbinden et al, 2007;Theissinger et al, 2009;Joseph and Shaw, 2011), multiple paternity in Atlantic leatherback clutches has been observed in low proportions (10-41.7%; Crim et al, 2002;Dutton, 2011, 2014;Figgener et al, 2016). Few instances of inter-nesting mating have been identified in leatherbacks (Figgener et al, 2016), and successive nests laid by most females reveal consistent paternities throughout the nesting season, indicative of sperm storage from mating event(s) occurring prior to the nesting season (Crim et al, 2002;Stewart and Dutton, 2011;Figgener et al, 2016). Therefore, male leatherbacks must intercept reproductive females upon arrival in low latitude waters prior to the onset of nesting, highlighting the importance of leatherback high-use areas prior to the nesting season.…”

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

“…For example, began a long-term genetic CMR effort in 2009 with leatherback hatchlings at Sandy Point National Wildlife Refuge (US Virgin Islands) with the goal of livesampling every hatchling leaving the nesting beach. Genetic fingerprints developed through the use of microsatellites (Stewart and Dutton, 2011) were applied to DNA from the hatchling samples to identify each one individually, effectively serving as a lifelong genetic "tag." Concurrently, they sampled and genetically fingerprinted each new nesting female at Sandy Point with the same microsatellite markers to identify when the former hatchlings return as nesting adults Dutton, 2011, 2014).…”

“…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.…”

“…Genetic studies on males may be undertaken in conjunction with other methods, such as satellite tracking (Hays et al, , 2014b to improve estimates of breeding sex ratios across populations and to answer questions about site fidelity and how rookeries are connected to form populations. By identifying males that have made reproductive contributions to each clutch, we can also assign individual hatchlings to fathers and assess the relative contributions by different fathers (for clutches with multiple paternity), and therefore gain insight on reproductive strategies and success for the males as well as the females (Stewart and Dutton, 2011). However, complementary studies sampling in-water males at breeding grounds are needed to assess the number of males in the population with no reproductive success (e.g., due to competition).…”