Lasala Jacob A, Hughes Colin R, Wyneken Jeanette
Department of Biology, Florida Atlantic University, Boca Raton, Florida, United States of America.
PLoS One. 2018 Jan 25;13(1):e0191615. doi: 10.1371/journal.pone.0191615. eCollection 2018.
Species that display temperature-dependent sex determination are at risk as a result of increasing global temperatures. For marine turtles, high incubation temperatures can skew sex ratios towards females. There are concerns that temperature increases may result in highly female-biased offspring sex ratios, which would drive a future sex ratio skew. Studying the sex ratios of adults in the ocean is logistically very difficult because individuals are widely distributed and males are inaccessible because they remain in the ocean. Breeding sex ratios (BSR) are sought as a functional alternative to study adult sex ratios. One way to examine BSR is to determine the number of males that contribute to nests. Our goal was to evaluate the BSR for loggerhead turtles (Caretta caretta) nesting along the eastern Gulf of Mexico in Florida, from 2013-2015, encompassing three nesting seasons. We genotyped 64 nesting females (approximately 28% of all turtles nesting at that time) and up to 20 hatchlings from their nests (n = 989) using 7 polymorphic microsatellite markers. We identified multiple paternal contributions in 70% of the nests analyzed and 126 individual males. The breeding sex ratio was approximately 1 female for every 2.5 males. We did not find repeat males in any of our nests. The sex ratio and lack of repeating males was surprising because of female-biased primary sex ratios. We hypothesize that females mate offshore of their nesting beaches as well as en route. We recommend further comparisons of subsequent nesting events and of other beaches as it is imperative to establish baseline breeding sex ratios to understand how growing populations behave before extreme environmental effects are evident.
由于全球气温上升，表现出温度依赖型性别决定的物种面临风险。对于海龟来说，高孵化温度会使性别比例偏向雌性。人们担心温度升高可能导致后代性别比例严重偏向雌性，从而导致未来性别比例失衡。在海洋中研究成年海龟的性别比例在后勤上非常困难，因为个体分布广泛，而且雄性海龟难以接触到，因为它们一直生活在海洋中。繁殖性别比例（BSR）被视为研究成年性别比例的一种有效替代方法。研究BSR的一种方法是确定参与筑巢的雄性数量。我们的目标是评估2013年至2015年在佛罗里达州墨西哥湾东部筑巢的蠵龟（Caretta caretta）的繁殖性别比例，涵盖三个筑巢季节。我们使用7个多态微卫星标记对64只筑巢雌性海龟（约占当时所有筑巢海龟的28%）及其巢穴中多达20只幼龟（n = 989）进行了基因分型。我们在70%的分析巢穴中发现了多个父系贡献，并识别出126只个体雄性。繁殖性别比例约为每2.5只雄性对应1只雌性。我们在任何巢穴中都没有发现重复出现的雄性。由于初生性别比例偏向雌性，这种性别比例和缺乏重复雄性的情况令人惊讶。我们假设雌性在其筑巢海滩外以及途中进行交配。我们建议进一步比较后续的筑巢事件和其他海滩，因为建立基线繁殖性别比例对于了解在极端环境影响显现之前不断增长的种群行为至关重要。
