Conservation of Ovary-Specific Genes, Foxl2, Aromatase, and Rspo1, in the Common Indian Garden Lizard, Calotes versicolor, That Lacks Chromosomal or Temperature-Dependent Sex Determination

The discovery in mammals that fetal testes are required in order to develop the male phenotype inspired research efforts to elucidate the mechanisms underlying gonadal sex determination and differentiation in vertebrates. A pioneer work in 1966 that demonstrated the influence of incubation temperature on sexual phenotype in some reptilian species triggered great interest in the environment’s role as a modulator of plasticity in sex determination. Several chelonian species have been used as animal models to test hypotheses concerning the mechanisms involved in temperature-dependent sex determination (TSD). This brief review intends to outline the history of scientific efforts that corroborate our current understanding of the state-of-the-art in TSD using chelonian species as a reference.

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Variation in nesting patterns affecting nest temperatures in two populations of painted turtles (Chrysemys picta) with temperature-dependent sex determination

Behavioral Ecology and Sociobiology ◽

10.1007/s00265-002-0570-3 ◽

2003 ◽

Vol 53 (4) ◽

pp. 254-261 ◽

Cited By ~ 63

Author(s):

Carrie L. Morjan

Keyword(s):

Sex Determination ◽

Chrysemys Picta ◽

Temperature Dependent ◽

Painted Turtles ◽

Nesting Patterns ◽

Two Populations

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Evolutionary transitions between mechanisms of sex determination in vertebrates

Biology Letters ◽

10.1098/rsbl.2010.1126 ◽

2011 ◽

Vol 7 (3) ◽

pp. 443-448 ◽

Cited By ~ 62

Author(s):

Alexander E. Quinn ◽

Stephen D. Sarre ◽

Tariq Ezaz ◽

Jennifer A. Marshall Graves ◽

Arthur Georges

Keyword(s):

Sex Determination ◽

Chromosome Pair ◽

Sex Chromosome ◽

Molecular Pathways ◽

Genetic Contribution ◽

Temperature Dependent ◽

Trait Evolution ◽

Evolutionary Transitions ◽

Dichotomous Outcome ◽

Threshold Trait

Sex in many organisms is a dichotomous phenotype—individuals are either male or female. The molecular pathways underlying sex determination are governed by the genetic contribution of parents to the zygote, the environment in which the zygote develops or interaction of the two, depending on the species. Systems in which multiple interacting influences or a continuously varying influence (such as temperature) determines a dichotomous outcome have at least one threshold. We show that when sex is viewed as a threshold trait, evolution in that threshold can permit novel transitions between genotypic and temperature-dependent sex determination (TSD) and remarkably, between male (XX/XY) and female (ZZ/ZW) heterogamety. Transitions are possible without substantive genotypic innovation of novel sex-determining mutations or transpositions, so that the master sex gene and sex chromosome pair can be retained in ZW–XY transitions. We also show that evolution in the threshold can explain all observed patterns in vertebrate TSD, when coupled with evolution in embryonic survivorship limits.

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