The Evolution of Sex Determination in Animals

Mank, Judith E.; Uller, Tobias

doi:10.1002/9781118707449.ch2

Cited by 3 publications

(4 citation statements)

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“…and provides a unique framework to investigate how complex geneenvironment interaction shape phenotypes and ecological responses to environmental variation (Capel, 2017;Mank & Uller, 2014;Pen et al, 2010). Here, we documented for the first time that water restriction can override heterogametic sex determination in two viviparous species known to display GSD (Aprea et al, 2006;Chevalier et al, 1979).…”

Section: Esd Is One Of the Most Striking Examples Of Developmental Plmentioning

confidence: 85%

“…Although most animal species have been historically classified with either GSD or ESD, both strategies are now treated as extremes of a continuum of relative influence between genotypic and environmental factors (Capel, 2017;Mank & Uller, 2014;Pen et al, 2010). For example, cases of environmental sex reversal offer striking examples of labile interactions between GSD and ESD, whereby the genetic sex is environmentally reversed during ontogeny (Stelkens & Wedekind, 2010).…”

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confidence: 99%

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Some like it dry: Water restriction overrides heterogametic sex determination in two reptiles

Dupoué

Lourdais

Meylan

et al. 2019

Ecology and Evolution

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The evolution of sex determination is complex and yet crucial in our understanding of population stability. In ectotherms, sex determination involves a variety of mechanisms including genetic determination (GSD), environment determination (ESD), but also interactions between the two via sex reversal. In this study, we investigated whether water deprivation during pregnancy could override GSD in two heterogametic squamate reptiles. We demonstrated that water restriction in early gestation induced a male‐biased secondary sex ratio in both species, which could be explained by water sex reversal as the more likely mechanism. We further monitored some long‐term fitness estimates of offspring, which suggested that water sex determination (WSD) represented a compensatory strategy producing the rarest sex according to Fisher's assumptions of frequency‐dependent selection models. This study provides new insights into sex determination modes and calls for a general investigation of mechanisms behind WSD and to examine the evolutionary implications. OPEN RESEARCH BADGES This article has earned an Open Data Badge for making publicly available the digitally‐shareable data necessary to reproduce the reported results. The data is available at https://doi.org/10.5061/dryad.mv06pv1.

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Section: Esd Is One Of the Most Striking Examples Of Developmental Plmentioning

confidence: 85%

mentioning

confidence: 99%

Some like it dry: Water restriction overrides heterogametic sex determination in two reptiles

Dupoué

Lourdais

Meylan

et al. 2019

Ecology and Evolution

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“…We argue that, in addition to the proposed pathway of vertebrate sex chromosome evolution, the evolution of sex chromosomes in reptiles has also occurred via other molecular mechanisms, particularly subtle gene regulatory mechanisms (e.g., epimutations, i.e., abnormal transcriptional repression of active genes and/or abnormal activation of usually repressed genes caused by errors in epigenetic gene repression [ 137 ], evolution of sexually antagonistic genes, e.g., [ 53 , 138 ]). This perhaps suggests reptiles possess a plasticity in maintaining sex ratios in highly labile environments ( Figure 2 ), which would somewhat explain the maintenance of TSD, transitions between TSD and GSD as well as temperature mediated sex reversal in GSD species with cryptic ( P. vitticeps ) and heteromorphic sex chromosomes ( B. duperreyi ).…”

Section: Unique Pathway Of Sex Chromosome Evolution In Lizards—a Dmentioning

confidence: 99%

Did Lizards Follow Unique Pathways in Sex Chromosome Evolution?

Alam

Sarre

Gleeson

et al. 2018

Genes

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Reptiles show remarkable diversity in modes of reproduction and sex determination, including high variation in the morphology of sex chromosomes, ranging from homomorphic to highly heteromorphic. Additionally, the co-existence of genotypic sex determination (GSD) and temperature-dependent sex determination (TSD) within and among sister clades makes this group an attractive model to study and understand the evolution of sex chromosomes. This is particularly so with Lizards (Order Squamata) which, among reptiles, show extraordinary morphological diversity. They also show no particular pattern of sex chromosome degeneration of the kind observed in mammals, birds and or even in snakes. We therefore speculate that sex determination sensu sex chromosome evolution is labile and rapid and largely follows independent trajectories within lizards. Here, we review the current knowledge on the evolution of sex chromosomes in lizards and discuss how sex chromosome evolution within that group differs from other amniote taxa, facilitating unique evolutionary pathways.

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“…Although an individual's sex is influenced by contributions from both genetic and environmental factors (Sarre, Georges & Quinn, ), SDMs have traditionally been categorized as either genotypic sex determination (GSD) or environmental sex determination (ESD). This dichotomous classification oversimplifies the complexity of SDMs, but can be useful for understanding the phylogenetic history of SDM evolution (Janzen & Krenz, ; Pokorná & Kratochvíl, ; Mank & Uller, ). However, some recent studies of reptile sex determination suggest that ESD and GSD systems are ends of a continuum, in which differences between the systems could relate to the control of dosage‐dependent expression of sex‐determining genes (Sarre et al ., ; Quinn et al ., ; Ezaz et al ., ; Holleley et al ., ).…”

Section: Introductionmentioning

confidence: 99%

Revisiting the first report of temperature‐dependent sex determination in a vertebrate, the African redhead agama

2018

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Vertebrates display a wide variety of sex-determining mechanisms (SDMs). Identifying SDMs for different taxa is important for understanding the origins and phylogenetic history of sex-determining mechanisms. Temperature-dependent sex determination (TSD) is found in several vertebrate and invertebrate species, and has been studied most extensively in reptiles. The initial discovery of TSD was in a lizard, the African redhead agama (Agama agama), over 50 years ago. The original study of A. agama used only two incubation temperature treatments and had a small sample size, thus it could not fully characterize the pattern of TSD in this species. The goal of this study is to revisit this research to better characterize the pattern of TSD. We also assessed the effect of fluctuating incubation temperatures on offspring sex ratio to provide insight into how variation in offspring sex ratio is produced under natural conditions. After incubating eggs across six constant temperature treatments, we demonstrated that females are produced at relatively cool temperatures and males at warmer temperatures (30°C); fluctuating thermal regimes showed this same pattern. However, some females are again produced at even warmer temperatures, resulting in relatively balanced sex ratios toward the end of the sex-determining reaction norm. Though the shape of the sex-determining reaction norm shown here is unusual, it shows some similarities to that of other agamid lizards. Future studies that explore the diversity of TSD reaction norms and underlying physiological mechanisms will provide new insights into the evolution of TSD.

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The Evolution of Sex Determination in Animals

Cited by 3 publications

References 115 publications

Some like it dry: Water restriction overrides heterogametic sex determination in two reptiles

Some like it dry: Water restriction overrides heterogametic sex determination in two reptiles

Did Lizards Follow Unique Pathways in Sex Chromosome Evolution?

Revisiting the first report of temperature‐dependent sex determination in a vertebrate, the African redhead agama

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