Abstract
Understanding species’ mating systems provides important information about their ecology, life history, and behavior. Direct observations of mating behaviors can be challenging, but molecular techniques can reveal information about mating systems and paternal identity in difficult-to-observe species such as sea turtles. Genetic markers can be used to assess the paternity of a clutch and to assign hatchlings to a father. Leatherback turtles Dermochelys coriacea sometimes mate with multiple individuals, resulting in clutches with mixed paternity; however, the effects of multiple paternity on hatchling quality are unclear. Leatherback hatchlings at Sandy Point National Wildlife Refuge, St. Croix, US Virgin Islands, exhibit visible variation in individual body size, sometimes within the same clutch. We collected morphometrics and tissue samples from hatchlings across multiple nesting seasons (2009, 2012, 2013, 2015, and 2016) and found that hatchlings exhibited small but statistically significant differences in morphometrics between years. We used maternal and hatchling microsatellite genotypes to reconstruct paternal genotypes, assigning fathers to each hatchling. We found multiple paternity in 5 of 17 clutches analyzed and compared differences in morphometrics between full-siblings with differences between half-siblings. We found no significant differences between morphometrics of hatchlings from the same mother but different fathers. We compared within-clutch variances in morphometrics for clutches with and without multiple paternity and found no significant difference in morphological variation between them. Therefore, we could not attribute differences in hatchling size within a clutch to paternal contribution. Understanding other factors affecting hatchling morphology, and other possible fitness metrics, may reveal insights into the benefits, or lack thereof, of polyandry in sea turtles.
Highlights
Investigating relationships between paternity and offspring fitness can be challenging, as both measurements of fitness and direct observations of paternity can be difficult to obtain in species where individuals are not observed in the wild
We addressed the following objectives: (1) What is the variation in morphology for leatherback hatchlings at Sandy Point National Wildlife Refuge (SPNWR), and does it vary by year? (2) Is morphological variation within a clutch of leatherback sea turtle hatchlings in multiple paternity clutches related to paternal identity? (3) Do clutches with multiple paternity have greater morphological variation among hatchlings? If hatchling body size is related to paternal identity, we would expect to detect differences in morphometrics between hatchlings with different fathers from the same clutch
We evaluated differences in mass, SCL, SCW, BD, and body condition index (BCI) based on paternal identity between individuals within each clutch that exhibited multiple paternity and had paired genetic and morphological data (Table S1, Objective 2)
Summary
Investigating relationships between paternity and offspring fitness can be challenging, as both measurements of fitness and direct observations of paternity can be difficult to obtain in species where individuals are not observed in the wild. Molecular techniques can provide insights into paternity and mating systems of hard-to-observe species (Lee 2008). These types of data indicate that multiple paternity is a common phenomenon across many taxa and is found in 50% of non-avian reptile clutches (Uller & Olsson 2008). Some data show positive correlations between multiple paternity and traits used to determine fitness, such as chick survivorship in blue tits Parus carrulus (Kempenaers et al 1997) and clutch size in painted turtles Chrysemys picta (Pearse et al 2002), but there has been little evidence for direct or indirect fitness advantages from multiple paternity in marine turtle species (Lee et al 2018)
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