Genotypic sex determination enabled adaptive radiations of extinct marine reptiles

  title={Genotypic sex determination enabled adaptive radiations of extinct marine reptiles},
  author={Christopher Lee Organ and Daniel E. Janes and Andrew Meade and Mark Pagel},
Adaptive radiations often follow the evolution of key traits, such as the origin of the amniotic egg and the subsequent radiation of terrestrial vertebrates. The mechanism by which a species determines the sex of its offspring has been linked to critical ecological and life-history traits but not to major adaptive radiations, in part because sex-determining mechanisms do not fossilize. Here we establish a previously unknown coevolutionary relationship in 94 amniote species between sex… 

Variability in Sex-Determining Mechanisms Influences Genome Complexity in Reptilia

It is suggested that evolutionary changes in sex determination provide a foundation for understanding important aspects of chromosome and genome organization that otherwise appear haphazard in their origins and contents.

Gonadal Differentiation in Reptiles Exhibiting Environmental Sex Determination

As temperature-dependent sex determination (TSD) and homozygote or heterozygote genetic sex determination (GSD) exist in multiple reptilian taxa, they represent sex determination systems that have


It is shown that rates of evolution in turtle chromosome number are ∼20‐fold higher along phylogenetic branches where transitions between sex‐determining mechanisms also occur, revealing a strong coevolution of these traits and making drift a less likely driver.

Are evolutionary transitions in sexual size dimorphism related to sex determination in reptiles?

The results support the prediction that sexual size dimorphism is linked to sex‐dependent developmental variations caused by environmental factors and also by sex chromosomes.

Sex determination systems in reptiles are related to ambient temperature but not to the level of climatic fluctuation

It is shown that ambient temperature is important during breeding seasons and it helps explain the effects of sex determination systems on the geographic distribution of extant reptile species.

Molecular evolution of Dmrt1 accompanies change of sex-determining mechanisms in reptilia

A consistent molecular difference is shown in Dmrt1 between reptiles with genotypic and temperature-dependent sex determination, suggesting that a convergently evolved pair of amino acids encoded by sequence within exon 2 near the DM-binding domain of DmRT1 distinguishes species with either type of sex determination.

Causes and Consequences of Evolutionary Transitions in the Level of Phenotypic Plasticity of Reptilian Sex Determination

The flourish of genomic approaches applied to the study of sex determination along with the refinement of phylogenetic comparative methods are enabling the reconstruction of the enigmatic micro- and macroevolutionary history of reptilian sex determination.

A brief review of vertebrate sex evolution with a pledge for integrative research: towards ‘sexomics’

An up-to-date review of divergence times, species diversity, genomic resources, genome size, occurrence and nature of polyploids, SD systems, sex chromosomes, SD genes, dosage compensation and sex-biased gene expression across major clades of vertebrates is offered.

Chapter 1 Sex Determination in Reptiles

The goal of this chapter is to integrate studies from different disciplines to broadly summarize the current understanding of reptilian sex determination and current gaps in this field and where future research should be directed.



The adaptive significance of temperature-dependent sex determination in a reptile

The first substantial empirical support for the Charnov–Bull model for the adaptive significance of temperature-dependent sex determination in amniote vertebrates is provided by showing that incubation temperatures influence reproductive success of males differently than that of females in a short-lived lizard with temperature- dependent sex determination.

Evolution of sex chromosomes in Sauropsida.

This work finds support for the common ancestor of amphisbaenians and whiptail lizards possessing the XY GSD mechanism, while the ancestors of Testudines and Crocodylia, as well as the larger group Archosauromorpha are inferred to have exhibited TSD.

Natural History of Reptilian Development: Constraints on the Evolution of Viviparity

Observed observations are consistent with both a saltation model that posits that the characteristic features of viviparity arise suddenly and simultaneously, and a gradualist model that Posits incremental evolution from one reproductive mode to the other.

Exploring the evolution of environmental sex determination, especially in reptiles

The latest empirical findings in lizards and turtles, as well as promising experimental results from a model organism, that portend an exciting future of progress in finally elucidating the evolutionary cause(s) and significance of TSD.

Live birth in Cretaceous marine lizards (mosasauroids)

  • M. CaldwellM. S. Lee
  • Environmental Science, Geography
    Proceedings of the Royal Society of London. Series B: Biological Sciences
  • 2001
Viviparity in early medium-sized amphibious aigialosaurs may have freed them from the need to return to land to deposit eggs, and permitted the subsequent evolution of gigantic totally marine mosasaurs.

Triassic marine reptiles gave birth to live young

Two gravid specimens of Keichousaurus hui Young from the Middle Triassic of China provide the first unequivocal evidence of reproductive mode and sexual dimorphism in sauropterygians and indicate that viviparity could have been expedited by the evolution of a movable pelvis in pachypleurosaurs.

Evolutionary Origins of Viviparity in the Reptilia. I. Sauria

Reproductive mode data were extracted piecemeal from the literature and superimposed over currently accepted phylogenies to permit estimation of the minimum frequencies with which viviparity (live-bearing) has evolved in lizards, as well as to facilitate analysis of hypotheses that genetic sex-determination of the male-heterogametic type as weil as a tendency towards eggention preadapt a lineage for v Viviparity.

Temperature Sex Reversal Implies Sex Gene Dosage in a Reptile

It is shown that high incubation temperatures reverse genotypic males to phenotypic females in a lizard with ZZ and ZW sex chromosomes, suggesting that sex chromosomes may exist in many TSD reptiles.

Evolution of Fish-Shaped Reptiles (reptilia: Ichthyopterygia) in Their Physical Environments and Constraints

Ichthyosaurs were a group of Mesozoic marine reptiles that evolved fish-shaped body outlines that allowed estimation of such characteristics as optimal cruising speed, visual sensitivity, and even possible basal metabolic rate ranges.

Maternal basking behaviour determines offspring sex in a viviparous reptile

These studies on the viviparous lizard Niveoscincus ocellatus show that the extent of basking by a female influences the sex of her offspring, and changes in thermoregulatory behaviour thus allow pregnant female lizards to modify thesex of their offspring.