Agricultural practices alter sex ratios in a reptile with environmental sex determination

Freedberg, Steven; Lee, Chee Khoon; Pappas, Michael

doi:10.1016/j.biocon.2011.01.001

Cited by 25 publications

(31 citation statements)

References 37 publications

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“…Still, because hatchlings cannot feasibly be marked in such a way that is discernable several years later, we cannot confirm individual identity or hatching site of primiparous females recruited into our population. In addition, there is conflicting evidence regarding sex-differential mortality between hatching and breeding and its potential role in modifying adult sex ratios (Weisrock andJanzen 1999, Freedberg andBowne 2006). However, it is clear that recruitment of female hatchlings in our population augments the number of breeding females many years later when they mature.…”

Section: Discussionmentioning

confidence: 99%

Climate and predation dominate juvenile and adult recruitment in a turtle with temperature‐dependent sex determination

Schwanz

Spencer

Bowden

et al. 2010

Ecology

123

158

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Conditions experienced early in life can influence phenotypes in ecologically important ways, as exemplified by organisms with environmental sex determination. For organisms with temperature-dependent sex determination (TSD), variation in nest temperatures induces phenotypic variation that could impact population growth rates. In environments that vary over space and time, how does this variation influence key demographic parameters (cohort sex ratio and hatchling recruitment) in early life stages of populations exhibiting TSD? We leverage a 17-year data set on a population of painted turtles, Chrysemys picta, to investigate how spatial variation in nest vegetation cover and temporal variation in climate influence early lifehistory demography. We found that spatial variation in nest cover strongly influenced nest temperature and sex ratio, but was not correlated with clutch size, nest predation, total nest failure, or hatching success. Temporal variation in climate influenced percentage of total nest failure and cohort sex ratio, but not depredation rate, mean clutch size, or mean hatching success. Total hatchling recruitment in a year was influenced primarily by temporal variation in climate-independent factors, number of nests constructed, and depredation rate. Recruitment of female hatchlings was determined by stochastic variation in nest depredation and annual climate and also by the total nest production. Overall population demography depends more strongly on annual variation in climate and predation than it does on the intricacies of nest-specific biology. Finally, we demonstrate that recruitment of female hatchlings translates into recruitment of breeding females into the population, thus linking climate (and other) effects on early life stages to adult demographics. Abstract. Conditions experienced early in life can influence phenotypes in ecologically important ways, as exemplified by organisms with environmental sex determination. For organisms with temperature-dependent sex determination (TSD), variation in nest temperatures induces phenotypic variation that could impact population growth rates. In environments that vary over space and time, how does this variation influence key demographic parameters (cohort sex ratio and hatchling recruitment) in early life stages of populations exhibiting TSD? We leverage a 17-year data set on a population of painted turtles, Chrysemys picta, to investigate how spatial variation in nest vegetation cover and temporal variation in climate influence early life-history demography. We found that spatial variation in nest cover strongly influenced nest temperature and sex ratio, but was not correlated with clutch size, nest predation, total nest failure, or hatching success. Temporal variation in climate influenced percentage of total nest failure and cohort sex ratio, but not depredation rate, mean clutch size, or mean hatching success. Total hatchling recruitment in a year was influenced primarily by temporal variation in climate-independent factors, number of...

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Section: Discussionmentioning

confidence: 99%

Climate and predation dominate juvenile and adult recruitment in a turtle with temperature‐dependent sex determination

Schwanz

Spencer

Bowden

et al. 2010

Ecology

123

158

View full text Add to dashboard Cite

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“…In reptiles with TSD there is now abundant evidence that unusually warm years produce hatchling sex ratios that are skewed towards the sex produced near the upper limit of tolerated incubation temperatures [Mrosovsky and Provancha, 1992;Janzen, 1994;Freedberg and Wade, 2001;Hays et al, 2003;Glen and Mrosovsky, 2004;Doody et al, 2006;Freedberg and Bowne, 2006;Hawkes et al, 2007;Wapstra et al, 2009]. This trend may exist despite any associated behavioural response to a warmer year (such as earlier nesting) and clearly demonstrates that, without a microevolutionary shift in threshold temperatures or subsequent nesting behaviour, climate warming is likely to produce cohorts of hatchlings where sex ratios are significantly skewed.…”

Section: Sex Ratio Bias Leading To Demographic Collapsementioning

confidence: 90%

Temperature-Dependent Sex Determination and Contemporary Climate Change

Mitchell

Janzen

2010

Sex Dev

176

182

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Whether species that have persisted throughout historic climatic upheavals will survive contemporary climate change will depend on their ecological and physiological traits, their evolutionary potential, and potentially upon the resources that humans commit to prevent their extinction. For those species where temperatures influence sex determination, rapid global warming poses a unique risk of skewed sex ratios and demographic collapse. Here we review the specific mechanisms by which reptiles with temperature-dependent sex determination (TSD) may be imperilled at current rates of warming, and discuss the evidence for and against adaptation via behavioural or physiological means. We propose a scheme for ranking reptiles with TSD according to their vulnerability to rapid global warming, but note that critical data on the lability of the sex determining mechanism and on the heritability of behavioural and threshold traits are unavailable for most species. Nevertheless, we recommend a precautionary approach to management of reptiles identified as being at relatively high risk. In such cases, management should aim to neutralise directional sex ratio biases (e.g. by manipulating incubation temperatures or assisted migration) and promote adaptive processes, possibly by genetic supplementation of populations. These practices should aid species’ persistence and buy time for research directed at more accurate prediction of species’ vulnerability.

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“…Many populations of species with TSD already exhibit offspring sex ratios skewed towards the sex produced at warmer temperatures, e.g. males in tuatara [3] and females in marine and freshwater turtle populations [4,5]. Future climate change scenarios are predicted to increase these sex ratio biases, with implications for population viability [2,3,6,7].…”

Section: Introductionmentioning

confidence: 99%

Turtle mating patterns buffer against disruptive effects of climate change

et al. 2012

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For organisms with temperature-dependent sex determination (TSD), skewed offspring sex ratios are common. However, climate warming poses the unique threat of producing extreme sex ratio biases that could ultimately lead to population extinctions. In marine turtles, highly female-skewed hatchling sex ratios already occur and predicted increases in global temperatures are expected to exacerbate this trend, unless species can adapt. However, it is not known whether offspring sex ratios persist into adulthood, or whether variation in male mating success intensifies the impact of a shortage of males on effective population size. Here, we use parentage analysis to show that in a rookery of the endangered green turtle (Chelonia mydas), despite an offspring sex ratio of 95 per cent females, there were at least 1.4 reproductive males to every breeding female. Our results suggest that male reproductive intervals may be shorter than the 2 -4 years typical for females, and/or that males move between aggregations of receptive females, an inference supported by our satellite tracking, which shows that male turtles may visit multiple rookeries. We suggest that male mating patterns have the potential to buffer the disruptive effects of climate change on marine turtle populations, many of which are already seriously threatened.

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Agricultural practices alter sex ratios in a reptile with environmental sex determination

Cited by 25 publications

References 37 publications

Climate and predation dominate juvenile and adult recruitment in a turtle with temperature‐dependent sex determination

Climate and predation dominate juvenile and adult recruitment in a turtle with temperature‐dependent sex determination

Temperature-Dependent Sex Determination and Contemporary Climate Change

Turtle mating patterns buffer against disruptive effects of climate change

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