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Sex in the suburbs: The genetic and environmental drivers of sex determination in amphibians.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Sex in the suburbs: The genetic and environmental drivers of sex determination in amphibians./
作者:	Lambert, Maxime Robert Michel.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2018,
面頁冊數:	195 p.
附註:	Source: Dissertations Abstracts International, Volume: 80-02, Section: B.
Contained By:	Dissertations Abstracts International80-02B.
標題:	Conservation biology. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=10927823
ISBN:	9780438193932

Sex in the suburbs: The genetic and environmental drivers of sex determination in amphibians.
Lambert, Maxime Robert Michel.

Sex in the suburbs: The genetic and environmental drivers of sex determination in amphibians. - Ann Arbor : ProQuest Dissertations & Theses, 2018 - 195 p.

Source: Dissertations Abstracts International, Volume: 80-02, Section: B.

Thesis (Ph.D.)--Yale University, 2018.

This item must not be added to any third party search indexes.

Across vertebrate taxa, the mechanisms underlying how individuals develop into one sex or another are remarkably variable. At one end of the spectrum, sex determination can be strictly genotypic, as observed in all mammals and birds, relying solely on genes to trigger sexual development. At the other end of this spectrum are taxa with strict environmental sex determination, as in seen in all crocodilians and most turtles, where sexual differentiation is entirely controlled by rearing conditions, like temperature. Across this spectrum are other vertebrates, like many fishes and squamates, which have combined genotypic and environmental contributions to sex determination. In these taxa, rearing conditions can cause individuals do develop their phenotypic sex opposite their genotypic sex - they sex reverse. All amphibians studied to date have a genotypic basis to sex. Yet, a wealth of experimental research has shown that amphibian sexual development is sensitive to environmental conditions. Even so, it is generally considered that environmentally-sensitive sexual development in amphibians is an aberrant response to anthropogenic contaminants or extreme temperature in laboratory venues. Previously, myself and colleagues reported a unique pattern: at metamorphosis, green frog (Rana clamitans) sex ratios were consistently male-biased in several ponds surrounded by entirely forested environments and became more dominated by females as the surrounding landscape became increasingly comprised of residential suburban neighborhoods. This pattern illustrates that sex ratios of wild amphibian offspring cohorts can deviate from parity and vary with environmental conditions. Sex ratio variation is regularly considered evidence of sex reversal in laboratory experiments. In these studies, an overabundance of one phenotypic sex is assumed to be the result of sex reversal by individuals of the opposing genotypic sex. The sex ratio variation seen in green frog metamorphs therefore calls into question the assumed strict genetic basis to sex in amphibians and whether there is a larger role for the environment in sexual differentiation. The five chapters comprising this dissertation aim to tease apart the genetic and environmental contributions to sex determination in wild amphibian populations and to understand whether sex reversal is a contributing force underlying sex ratio variation. In chapters 1 and 2, I experimentally demonstrate that amphibian sex ratios, as well as sex-specific somatic development, are sensitive to relatively natural classes of chemicals. In particular, I show that the chemical mixtures naturally found in various plant tissues as well as sodium chloride, a common road de-icing salt, influence sex ratios, male metamorphic timing, and sexual size dimorphism. In chapter 3, I identified multiple sex-linked genetic markers for the North American green frog using DArTseq, a form of genome complexity reduction coupled with next generation sequencing. In chapter 4, I used these genetic sex markers to provide evidence that sex reversal is bidirectional and common in adult green frog cohorts inhabiting either undeveloped, forested ponds or heavily suburbanized ponds. This work demonstrates that sex determination in some amphibian species can have clear genetic and environmental contributions. Finally, in chapter 5, I tested whether sex reversal, in addition to sex allocation and sex-biased mortality, contributed to previously identified patterns of green frog metamorph sex ratio variation. I found that phenotypic sex ratios are variable across time and are not likely driven by sex reversal directly. Rather, I found that clutch sex ratios, and by extension cohort sex ratios, are comprised of a disproportionate number of genotypic males, indicating that metamorph phenotypic sex ratio biases may begin at fertilization. This suggests that sex-reversed phenotypic females may breed with sex-concordant males, thereby producing an abundance of sons. Sex ratio variation in offspring cohorts may therefore be a result of breeding by sex-reversed parents as well as sex reversal during larval development. This dissertation challenges the presiding paradigm that sex in amphibians in strictly genetic and highlights a novel role for environmentally-mediated sex determination and sex ratio variation in wild frogs. Collectively, my body of work demonstrates that sex reversal and unequal sex ratios are not necessarily responses to anthropogenic contaminants or extreme temperatures, but can be the product of natural environmental conditions. These findings begin to point towards sex reversal as an evolutionarily important process, perhaps being adaptive under certain conditions or facilitating the transitions among sex-determining modes. This research reshapes our understanding of the evolutionary history and ecological determinants of sex in amphibians and should encourage further investigation into the causes and consequences of sex ratio variation and sex reversal in taxa with combined genetic and environmental contributions to sexual development.

ISBN: 9780438193932Subjects--Topical Terms:

535736
Conservation biology.

Sex in the suburbs: The genetic and environmental drivers of sex determination in amphibians.
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300 $a 195 p.
500 $a Source: Dissertations Abstracts International, Volume: 80-02, Section: B.
500 $a Publisher info.: Dissertation/Thesis.
500 $a Advisor: Skelly, David K.
502 $a Thesis (Ph.D.)--Yale University, 2018.
506 $a This item must not be added to any third party search indexes.
506 $a This item must not be sold to any third party vendors.
520 $a Across vertebrate taxa, the mechanisms underlying how individuals develop into one sex or another are remarkably variable. At one end of the spectrum, sex determination can be strictly genotypic, as observed in all mammals and birds, relying solely on genes to trigger sexual development. At the other end of this spectrum are taxa with strict environmental sex determination, as in seen in all crocodilians and most turtles, where sexual differentiation is entirely controlled by rearing conditions, like temperature. Across this spectrum are other vertebrates, like many fishes and squamates, which have combined genotypic and environmental contributions to sex determination. In these taxa, rearing conditions can cause individuals do develop their phenotypic sex opposite their genotypic sex - they sex reverse. All amphibians studied to date have a genotypic basis to sex. Yet, a wealth of experimental research has shown that amphibian sexual development is sensitive to environmental conditions. Even so, it is generally considered that environmentally-sensitive sexual development in amphibians is an aberrant response to anthropogenic contaminants or extreme temperature in laboratory venues. Previously, myself and colleagues reported a unique pattern: at metamorphosis, green frog (Rana clamitans) sex ratios were consistently male-biased in several ponds surrounded by entirely forested environments and became more dominated by females as the surrounding landscape became increasingly comprised of residential suburban neighborhoods. This pattern illustrates that sex ratios of wild amphibian offspring cohorts can deviate from parity and vary with environmental conditions. Sex ratio variation is regularly considered evidence of sex reversal in laboratory experiments. In these studies, an overabundance of one phenotypic sex is assumed to be the result of sex reversal by individuals of the opposing genotypic sex. The sex ratio variation seen in green frog metamorphs therefore calls into question the assumed strict genetic basis to sex in amphibians and whether there is a larger role for the environment in sexual differentiation. The five chapters comprising this dissertation aim to tease apart the genetic and environmental contributions to sex determination in wild amphibian populations and to understand whether sex reversal is a contributing force underlying sex ratio variation. In chapters 1 and 2, I experimentally demonstrate that amphibian sex ratios, as well as sex-specific somatic development, are sensitive to relatively natural classes of chemicals. In particular, I show that the chemical mixtures naturally found in various plant tissues as well as sodium chloride, a common road de-icing salt, influence sex ratios, male metamorphic timing, and sexual size dimorphism. In chapter 3, I identified multiple sex-linked genetic markers for the North American green frog using DArTseq, a form of genome complexity reduction coupled with next generation sequencing. In chapter 4, I used these genetic sex markers to provide evidence that sex reversal is bidirectional and common in adult green frog cohorts inhabiting either undeveloped, forested ponds or heavily suburbanized ponds. This work demonstrates that sex determination in some amphibian species can have clear genetic and environmental contributions. Finally, in chapter 5, I tested whether sex reversal, in addition to sex allocation and sex-biased mortality, contributed to previously identified patterns of green frog metamorph sex ratio variation. I found that phenotypic sex ratios are variable across time and are not likely driven by sex reversal directly. Rather, I found that clutch sex ratios, and by extension cohort sex ratios, are comprised of a disproportionate number of genotypic males, indicating that metamorph phenotypic sex ratio biases may begin at fertilization. This suggests that sex-reversed phenotypic females may breed with sex-concordant males, thereby producing an abundance of sons. Sex ratio variation in offspring cohorts may therefore be a result of breeding by sex-reversed parents as well as sex reversal during larval development. This dissertation challenges the presiding paradigm that sex in amphibians in strictly genetic and highlights a novel role for environmentally-mediated sex determination and sex ratio variation in wild frogs. Collectively, my body of work demonstrates that sex reversal and unequal sex ratios are not necessarily responses to anthropogenic contaminants or extreme temperatures, but can be the product of natural environmental conditions. These findings begin to point towards sex reversal as an evolutionarily important process, perhaps being adaptive under certain conditions or facilitating the transitions among sex-determining modes. This research reshapes our understanding of the evolutionary history and ecological determinants of sex in amphibians and should encourage further investigation into the causes and consequences of sex ratio variation and sex reversal in taxa with combined genetic and environmental contributions to sexual development.
590 $a School code: 0265.
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650 4 $a Evolution and Development. $3 3422373
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