e-journal

What was the ancestral sex-determining mechanism in amniote vertebrates

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Amniote vertebrates, the group consisting of mammals and reptiles including birds, possess various mechanisms of sex
determination. Under environmental sex determination (ESD), the sex of individuals depends on the environmental
conditions occurring during their development and therefore there are no sexual differences present in their genotypes.
Alternatively, through the mode of genotypic sex determination (GSD), sex is determined by a sex-specific genotype,
i.e. by the combination of sex chromosomes at various stages of differentiation at conception. As well as influencing
sex determination, sex-specific parts of genomes may, and often do, develop specific reproductive or ecological roles
in their bearers. Accordingly, an individual with a mismatch between phenotypic (gonadal) and genotypic sex, for
example an individual sex-reversed by environmental effects, should have a lower fitness due to the lack of specialized,sex-specific parts of their genome. In this case, evolutionary transitions from GSD to ESD should be less likely than transitions in the opposite direction. This prediction contrasts with the view that GSD was the ancestral sex-determining mechanism for amniote vertebrates. Ancestral GSD would require several transitions from GSD to ESD associated with an independent dedifferentiation of sex chromosomes, at least in the ancestors of crocodiles, turtles, and lepidosaurs (tuataras and squamate reptiles). In this review, we argue that the alternative theory postulating ESD as ancestral in amniotes is more parsimonious and is largely concordant with the theoretical expectations and current knowledge of the phylogenetic distribution and homology of sex-determining mechanisms.

Key words: environmental sex determination, phylogeny, polyphenism, reptiles, Sauropsida, sex chromosomes, sex ratio,
sexual dimorphism.

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Informasi Detail

Judul Seri

Biol. Rev.

No. Panggil

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Penerbit

: Cambridge Philosophical Society., 2016

Deskripsi Fisik

Biol. Rev. (2016), 91, pp. 1–12

Bahasa

English

ISBN/ISSN

doi: 10.1111/brv.121

Klasifikasi

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Tipe Isi

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Tipe Media

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Tipe Pembawa

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Edisi

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Subjek

BIOLOGI

Info Detail Spesifik

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Pernyataan Tanggungjawab

Wati/Agus

Versi lain/terkait

Lampiran Berkas

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