Genetic Evidence for Co-occurrence of Chromosomal and Thermal Sex-determining Systems in a Lizard

Rajikumar Radder, Alex Quinn, Arthur Georges, Stephen Sarre, Richard Shine

    Research output: Contribution to journalArticle

    88 Citations (Scopus)

    Abstract

    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.
    Original languageEnglish
    Pages (from-to)176-178
    Number of pages3
    JournalBiology Letters
    Volume4
    Issue number2
    Publication statusPublished - 2008

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    Lizards
    lizards
    Hot Temperature
    heat
    gender
    Temperature
    Reptiles
    nests
    Eggs
    reptiles
    temperature
    Sex Chromosomes
    Scincidae
    Sex Ratio
    sex chromosomes
    Genetic Markers
    Birds
    estradiol
    Mammals
    Estradiol

    Cite this

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    title = "Genetic Evidence for Co-occurrence of Chromosomal and Thermal Sex-determining Systems in a Lizard",
    abstract = "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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    language = "English",
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    Genetic Evidence for Co-occurrence of Chromosomal and Thermal Sex-determining Systems in a Lizard. / Radder, Rajikumar; Quinn, Alex; Georges, Arthur; Sarre, Stephen; Shine, Richard.

    In: Biology Letters, Vol. 4, No. 2, 2008, p. 176-178.

    Research output: Contribution to journalArticle

    TY - JOUR

    T1 - Genetic Evidence for Co-occurrence of Chromosomal and Thermal Sex-determining Systems in a Lizard

    AU - Radder, Rajikumar

    AU - Quinn, Alex

    AU - Georges, Arthur

    AU - Sarre, Stephen

    AU - Shine, Richard

    PY - 2008

    Y1 - 2008

    N2 - 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.

    AB - 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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