Effects of Incubation Temperature on Sex Ratios in Pine Snakes: Differential Vulnerability of Males and Females

Burger, Joanna; Zappalorti, Robert T.

doi:10.1086/284867

Cited by 99 publications

(85 citation statements)

References 29 publications

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“…Conover 1984;Greer 1989;Ezaz et al 2005). In addition, shifts in offspring sex ratio can be generated by differential mortality rather than disruption of sex-determining systems (Burger & Zappalorti 1988). Given that female B. duperreyi are disadvantaged by cool temperature incubation (Shine et al 1995(Shine et al , 1997Elphick & Shine 1998), differential mortality offers a plausible mechanism to explain male-biased offspring sex ratios from cold incubation in this species also.…”

Section: Discussionmentioning

confidence: 99%

Genetic evidence for co-occurrence of chromosomal and thermal sex-determining systems in a lizard

et al. 2007

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An individual's sex depends upon its genes (genotypic sex determination or GSD) in birds and mammals, but reptiles are more complex: some species have GSD whereas in others, nest temperatures determine offspring sex (temperature-dependent sex determination). Previous studies suggested that montane scincid lizards (Bassiana duperreyi, Scincidae) possess both of these systems simultaneously: offspring sex is determined by heteromorphic sex chromosomes (XX-XY system) in most natural nests, but sex ratio shifts suggest that temperatures override chromosomal sex in cool nests to generate phenotypically male offspring even from XX eggs. We now provide direct evidence that incubation temperatures can sex-reverse genotypically female offspring, using a DNA sex marker. Application of exogenous hormone to eggs also can sex-reverse offspring (oestradiol application produces XY as well as XX females). In conjunction with recent work on a distantly related lizard taxon, our study challenges the notion of a fundamental dichotomy between genetic and thermally determined sex determination, and hence the validity of current classification schemes for sex-determining systems in reptiles.

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Section: Discussionmentioning

confidence: 99%

Genetic evidence for co-occurrence of chromosomal and thermal sex-determining systems in a lizard

et al. 2007

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“…(iii) Incubation environment. In egg-laying squamates, thermal and hydric conditions during incubation can substantially modify developmental rates (and thus, the timing of hatching) and also phenotypic traits of the offspring (Burger 1989(Burger , 1990(Burger , 1991(Burger , 1998Burger et al 1987;Burger & Zappalorti 1988). Thus, reproducing females directly influence the phenotypes of their offspring by selecting nest-sites with specific incubation conditions .…”

Section: (E) Offspring Qualitymentioning

confidence: 99%

Reproductive strategies in snakes

Shine

2003

Proc. R. Soc. Lond. B

267

199

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Snakes of both sexes display remarkable flexibility and diversity in their reproductive tactics. Many features of reproduction in female snakes (such as reproductive mode and frequency, seasonality and multiple mating) allow flexible maternal control. For example, females can manipulate not only the genotypes of their offspring (through mate choice or enhanced sperm competition) but also the phenotypes of their offspring (through allocation 'decisions', behavioural and physiological thermoregulation, and nest-site selection). Reliance on stored energy ('capital') to fuel breeding results in low frequencies of female reproduction and, in extreme cases, semelparity. A sophisticated vomeronasal system not only allows male snakes to locate reproductive females by following scent trails, but also facilitates pheromonally mediated mate choice by males. Male-male rivalry takes diverse forms, including female mimicry and mate guarding; combat bouts impose strong selection for large body size in males of some species. Intraspecific (geographical) variation and phenotypic plasticity in a wide array of reproductive traits (offspring size and number; reproductive frequency; incidence of multiple mating; male tactics such as mate guarding and combat; mate choice criteria) provide exceptional opportunities for future studies.

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“…Differential mortality as a function of incubation temperature has been reported in pine snakes, but death of embryos occurred late in development ( Burger and Zappalorti 1988). We discount egg mortality as a cause for the bias in hatchling sex ratio of tuatara.…”

Section: Pattern Of Tsd In Natural Nestsmentioning

confidence: 92%

“…However, vertebrate sex ratios can be distorted by various means, as when environmental factors override sex chromosomes. For instance, temperature-induced differential mortality (Burger and Zappalorti 1988), embryo abortion (e.g., Krackow 1992;Blackburn et al 1998), and differential fertilization (e.g., Komdeur et al 1997;Stockley 1999) can bias primary or secondary sex ratios (Valenzuela et al 2003). Temperature can also alter sex differentiation and induce sex reversal in species possessing sex chromosomes Baroiller et al 1995;Solari 1994; see also Chardard et al,Chapter 7), resulting in biased secondary sex ratios.…”

Section: Vertebrate Sex-determining Systemsmentioning

confidence: 99%