Highly feminised sex-ratio estimations for the world’s third-largest nesting aggregation of loggerhead sea turtles

Tanner, Claire; Marco, Adolfo; Martins, Samir; Abella-Perez, Elena; Hawkes, Lucy A.

doi:10.3354/meps12963

Cited by 45 publications

(31 citation statements)

References 39 publications

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“…Research on the effects of climate change on biodiversity has been disproportionately centred on terrestrial organisms (Feeley et al 2017), likely due to easier accessibility and accordingly better baseline data on both species and climate, yet numerous impacts on marine biodiversity have now been documented, from local to global scales (Poloczanska et al 2016, Worm & Lotze 2016, Crespo et al 2019). Most long-term studies have focussed on fish and plankton (Worm & Lotze 2016), with recent re search assessing impacts on large marine mega fauna (Erauskin-Extramiana et al 2019, Albouy et al 2020, corals (Hughes et al 2018), seagrasses (Chefaoui et al 2018), and seaweeds (Martins et al 2019).…”

Section: Introductionmentioning

confidence: 99%

Climate change and marine turtles: recent advances and future directions

Patrício

Hawkes

Monsinjon

et al. 2021

Endang. Species. Res.

Self Cite

104

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Climate change is a threat to marine turtles that is expected to affect all of their life stages. To guide future research, we conducted a review of the most recent literature on this topic, highlighting knowledge gains and research gaps since a similar previous review in 2009. Most research has been focussed on the terrestrial life history phase, where expected impacts will range from habitat loss and decreased reproductive success to feminization of populations, but changes in reproductive periodicity, shifts in latitudinal ranges, and changes in foraging success are all expected in the marine life history phase. Models have been proposed to improve estimates of primary sex ratios, while technological advances promise a better understanding of how climate can influence different life stages and habitats. We suggest a number of research priorities for an improved understanding of how climate change may impact marine turtles, including: improved estimates of primary sex ratios, assessments of the implications of female-biased sex ratios and reduced male production, assessments of the variability in upper thermal limits of clutches, models of beach sediment movement under sea level rise, and assessments of impacts on foraging grounds. Lastly, we suggest that it is not yet possible to recommend manipulating aspects of turtle nesting ecology, as the evidence base with which to understand the results of such interventions is not robust enough, but that strategies for mitigation of stressors should be helpful, providing they consider the synergistic effects of climate change and other anthropogenic-induced threats to marine turtles, and focus on increasing resilience.

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Section: Introductionmentioning

confidence: 99%

Climate change and marine turtles: recent advances and future directions

Patrício

Hawkes

Monsinjon

et al. 2021

Endang. Species. Res.

Self Cite

104

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show abstract

“…Furthermore, sex ratio assessments frequently use TSD curves from different nesting populations to infer the sex ratio at a particular location. [5,10,11] In addition, the thermosensitive period can shift from the middle third of incubation under fluctuating temperatures, which are typical in the nest of species that are shallower nesters. [12] As inaccurate estimations of sex ratios may affect the assessment of the overall impact of global warming on sea turtles, these limitations must be addressed to gain a clear understanding of the impact of climate change on these species.…”

Section: Doi: 101002/bies202000146mentioning

confidence: 99%

“…[1][2][3] Because sea turtles produce female hatchlings at high temperatures, numerous studies have warned about the ongoing and/or potential "feminization" of their populations under climate change. [3][4][5] Thus, the prevailing paradigm in climate change research on sea turtles is that they are threatened because they have TSD.…”

Section: Introduction: Temperature-dependent Sex Determination In a Wmentioning

confidence: 99%

Temperature‐Dependent Sex Determination in Sea Turtles in the Context of Climate Change: Uncovering the Adaptive Significance

Tomillo

Spotila

2020

BioEssays

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The adaptive significance of temperature-dependent sex determination (TSD) in reptiles remains unknown decades after TSD was first identified in this group. Concurrently, there is growing concern about the effect that rising temperatures may have on species with TSD, potentially producing extremely biased sex ratios or offspring of only one sex. The current state-of the-art in TSD research on sea turtles is reviewed here and, against current paradigm, it is proposed that TSD provides an advantage under warming climates. By means of coadaptation between early survival and sex ratios, sea turtles are able to maintain populations. When offspring survival declines at high temperatures, the sex that increases future fecundity (females) is produced, increasing resilience to climate warming. TSD could have helped reptiles to survive mass extinctions in the past via this model. Flaws in research on sex determination in sea turtles are also identified and it is suggested that the development of new techniques will revolutionize the field.

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“…There is a particular need to understand the impacts of climate change on the demographics of threatened species. As a consequence of rising temperatures, extreme feminisation of sea turtle populations has been forecast by the end of the century 4,[27][28][29] . Some studies suggest effects are already visible in adult populations 28 .…”

Section: Introductionmentioning

confidence: 99%

Maternally derived sex steroid hormones impact sex ratios of loggerhead sea turtles

Reischig²,

Eizaguirre

2020

Preprint

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An optimal sex ratio is arguably one of the most important demographic traits of species. Rising global temperatures threaten temperature-dependent sex determination (TSD) species with extreme sex ratio bias and ultimately extinction. Because sex steroid hormones can impact sex determination in TSD reptiles, variation in their maternal transfer within the egg yolk may form a buffer mechanism against raising temperatures. We tested this hypothesis by quantifying the effect of maternal oestradiol (E2) and testosterone (T) on offspring sex in a threatened TSD population of loggerhead sea turtles (Caretta caretta). Circulating levels of E2 and T in nesting females, in egg yolks at oviposition and in neonates were measured. Immediately after oviposition, nests were relocated into an in situ experimental hatchery where temperatures were controlled by standardising the incubation depth. We used affinity propagation clustering on hormone profiles guided by incubation duration, to sex individuals from these nests in a non-lethal manner, offering a novel conservation tool for this endangered species. Despite standardised temperatures, we found a large level of variation in the sex ratio of clutches, which correlated in a non-linear manner with maternal investment of the E2:T ratio in egg yolks. Males were produced at equal levels of E2 and T and females were produced on either side of this optimum. Modelling sex ratios for the coming century, we show that maternally-derived hormones form a trans-generational mechanism of TSD plasticity that adjusts offspring sex ratios in endangered sea turtles.

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Highly feminised sex-ratio estimations for the world’s third-largest nesting aggregation of loggerhead sea turtles

Cited by 45 publications

References 39 publications

Climate change and marine turtles: recent advances and future directions

Climate change and marine turtles: recent advances and future directions

Temperature‐Dependent Sex Determination in Sea Turtles in the Context of Climate Change: Uncovering the Adaptive Significance

Maternally derived sex steroid hormones impact sex ratios of loggerhead sea turtles

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