No evidence of fine scale thermal adaptation in green turtles

Tilley, Dominic; Ball, Samantha; Ellick, Jacqui; Godley, Brendan J.; Weber, Nicola; Weber, Sam; Broderick, Annette C.

doi:10.1016/j.jembe.2019.04.001

Cited by 22 publications

(17 citation statements)

References 62 publications

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“…Studies of TSD species suggest the answer to both questions is yes. Variation in sex ratio is correlated with nest or water temperatures in nature in crocodilians, lizards, turtles, and fish (Janzen, 1994;Weisrock and Janzen, 1999;Wapstra et al, 2009;Simoncini et al, 2014;Pezaro et al, 2016;Jensen et al, 2018;Patricio et al, 2018;Honeycutt et al, 2019;Mitchell and Janzen, 2019;Tilley et al, 2019). These studies indicate that TSD is operative in nature.…”

Section: Temperature Effects On Development Plasticity In Light Of Glmentioning

confidence: 71%

Embryonic Temperature Programs Phenotype in Reptiles

2020

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Reptiles are critically affected by temperature throughout their lifespan, but especially so during early development. Temperature-induced changes in phenotype are a specific example of a broader phenomenon called phenotypic plasticity in which a single individual is able to develop different phenotypes when exposed to different environments. With climate change occurring at an unprecedented rate, it is important to study temperature effects on reptiles. For example, the potential impact of global warming is especially pronounced in species with temperature-dependent sex determination (TSD) because temperature has a direct effect on a key phenotypic (sex) and demographic (population sex ratios) trait. Reptiles with TSD also serve as models for studying temperature effects on the development of other traits that display continuous variation. Temperature directly influences metabolic and developmental rate of embryos and can have permanent effects on phenotype that last beyond the embryonic period. For instance, incubation temperature programs post-hatching hormone production and growth physiology, which can profoundly influence fitness. Here, we review current knowledge of temperature effects on phenotypic and developmental plasticity in reptiles. First, we examine the direct effect of temperature on biophysical processes, the concept of thermal performance curves, and the process of thermal acclimation. After discussing these reversible temperature effects, we focus the bulk of the review on developmental programming of phenotype by temperature during embryogenesis (i.e., permanent developmental effects). We focus on oviparous species because eggs are especially susceptible to changes in ambient temperature. We then discuss recent work probing the role of epigenetic mechanisms in mediating temperature effects on phenotype. Based on phenotypic effects of temperature, we return to the potential impact of global warming on reptiles. Finally, we highlight key areas for future research, including the identification of temperature sensors and assessment of genetic variation for thermosensitivity.

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Section: Temperature Effects On Development Plasticity In Light Of Glmentioning

confidence: 71%

Embryonic Temperature Programs Phenotype in Reptiles

2020

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“…A review of thermal tolerances at different nesting sites indicated that there is a range of maximum values that is dependent on the location (Howard et al, 2014). However, a recent study suggests that there might not be a local adaptation to thermal tolerance limits, thus, increased nest temperatures under predicted climate change scenarios will result in increased embryo mortality and female hatchling production unless temporal or spatial range shifts occur (Tilley et al, 2019). In addition to mortality, high temperatures can cause reduced oxygen levels, which negatively affects muscle coordination, inhibiting the ability for turtles to crawl out of the nest (Matsuzawa, Sato, Sakamoto, & Bjorndal, 2002).…”

Section: Discussionmentioning

confidence: 99%

Potential feminization of Red Sea turtle hatchlings as indicated by in situ sand temperature profiles

Tanabe

Ellis

Elsadek

et al. 2020

Conservat Sci and Prac

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Climate change poses a serious threat to species that demonstrate temperature-dependent sex determination, including marine turtles. Increased temperatures can result in highly female-skewed sex ratios and decreased hatching success. The pivotal temperature that delineates hatchling sex ratios is commonly considered to be 29.2 C, but whether this threshold applies to turtles in the Red Sea region has not been tested in situ. For all species of marine turtles, there is a supposed thermal range of 25-33 C in which egg incubation is successful, with prolonged temperatures above 33 C resulting in morphological abnormalities and hatchling mortality. Sand temperature data were collected from May-September 2018 from the average nesting depth of hawksbill (Eretmochelys imbricata) and green turtles (Chelonia mydas) at five study sites. We calculated the expected sex ratio based on a maximum likelihood model. The sand temperature profile at four of the sites exceeded the pivotal temperature (29.2 C) throughout the study duration, which suggests feminization of turtles could be occurring; however, the pivotal temperature in this region still needs to be empirically confirmed. The percentage of days with sand temperature exceeding the maximum thermal threshold between June 3, and September 16, 2018, was site-specific rather than determined by latitudinal temperature gradients, and ranged between 0 and 100% of days. Maximum temperature recordings were as high as 36.0 and 35.3 C at 30 and 50 cm depth, respectively. Nesting sites in the Red Sea region could already be exceeding the thermal limits and may be particularly vulnerable to rising temperatures. Sites with lower sand temperatures, such as Small Gobal Island, may represent priority areas for conservation efforts. Alternatively, local adaptation may be a reality under extremely warm conditions, thus, further research into the thermal tolerance of hatchlings in the region could provide insight on how they might adapt to future climate change.

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“…For example, the pivotal temperatures for leatherbacks were estimated at 29.25-30.50 o C in Suriname and French Guiana (Mrosovsky et al 1984;Dutton et al 1985;Godfrey et al 1996;Chevalier et al 1999), in Malaysia (Chan andLiew 1995), andCosta Rica (Binckley et al 1998). Meanwhile, pivotal temperature in laboratory conditions for green turtles on Ascension Island was 29.3 o C (Tilley 2019). The beach temperatures observed at Venu Island and Lakahia may be within the thermal tolerance of turtle embryos, which results in the high hatching successes observed in clutches on Venu Island.…”

Section: Nest Temperaturesmentioning

confidence: 95%

Heavy metals contaminants in the eggs and temperatures of nesting beaches of sea turtles in Kaimana, West Papua, Indonesia

et al. 2020

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Abstract. Tapilatu RF, Wona H, Siburian RHS, Saleda ST. 2020. Heavy metals contaminants in the eggs and temperatures of nesting beaches of sea turtles in Kaimana, West Papua, Indonesia. Biodiversitas 21: 4582-4590. Etna Bay and Venu Island in Kaimana, West Papua, Indonesia are two of many areas that sea turtles use during the nesting season. Here, we report data on heavy metals contaminants from a sample of eggs of green (Chelonia mydas) and hawksbill (Eretmochelys imbricata) turtles collected from a subset of two nests during the 2016 nesting season at Venu Island, Kaimana, West Papua, Indonesia. Three heavy metals contaminants (i.e. mercury, cadmium, arsenic) found in eggs exceeded the established safety limits for human consumption. Other contaminants such as lead, zinc, manganese, iron, and copper were found below the established safety standards. There is an implication of the containment of heavy metals in sea turtle eggs to human health in Kaimana when it is consumed. It is highly recommended that the harvesting of turtle eggs and adults of all of sea turtles at Kaimana be totally prohibited. In addition, overall, beach temperatures in Lakahia fluctuated at a larger range between 26.5o and 33.8oC than at Venu island that fluctuated between 25.9o and 30.2oC. Mean daily temperatures of in-situ nests during the middle third of the incubation period were above the pivotal temperature of 29.0oC for temperature-dependent sex determination suggesting a female bias may already exist. The chemical contamination found in the eggs of C. mydas and E. imbricata at Venu Island is thought to assist sea turtle conservation initiatives in the area. The conservation program at the prime nesting habitat for green and hawksbill turtles on the small islands west of Kaimana such as Venu Island should be intensified to reverse the decline and increase population size of nesting sea turtle species. It is recommended that education and outreach be implemented in surrounding communities in Kaimana to raise awareness about marine turtle conservation.

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No evidence of fine scale thermal adaptation in green turtles

Cited by 22 publications

References 62 publications

Embryonic Temperature Programs Phenotype in Reptiles

Embryonic Temperature Programs Phenotype in Reptiles

Potential feminization of Red Sea turtle hatchlings as indicated by in situ sand temperature profiles

Heavy metals contaminants in the eggs and temperatures of nesting beaches of sea turtles in Kaimana, West Papua, Indonesia

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