Prevalence of polygyny in a critically endangered marine turtle population

Abstract Genetic analyses of nuclear DNA (e.g., microsatellites) are a primary tool for investigating mating systemsin reptiles, particularly marine turtles. Whereas studies over the past two decades have demonstrated that polyandry (i.e., females matingwith multiple males) is common in marine turtles, polygyny(i.e., males matingwith multiple females) has rarely been reported. In this study we investigated the matingstructure of Critically Endangered hawksbill turtles( Eretmochelys imbricata ) at Bahia de Jiquilisco in El Salvador, one of the largest rookeriesin the eastern Pacific Ocean. We collected genetic samples from 34 nesting females and hatchlingsfrom 41 clutches during the 2015 nesting season, including one nest from each of 27 females and two nests from seven additional females. Using six highly polymorphic microsatellite loci, we reconstructed the paternal genotypes for 22 known male turtles and discovered that seven (31.8%) sired nests from multiple females, which represents the highest polygynylevel reported to date for marine turtles and suggests that this is a common matingstructure for this population. We also detected multiple paternity in four (11.8%) clutches from the 34 females analyzed, confirming polyandrous matingstrategies are also employed. The high level of polygynywe documented suggests there may be a limited number of sexually mature males at Bahia de Jiquilisco; a scenario supported by multiple lines of empirical evidence. Our findings highlight key managementuncertainties, including whether polygynous matingstrategies can compensate for potential ongoing feminization and the low number of adult males found for this and possibly other marine turtle populations.