Extreme heterochiasmy and nascent sex chromosomes in European tree frogs.

We investigated sex-specific recombination rates in Hyla arborea, a species with nascent sex chromosomes and male heterogamety. Twenty microsatellites were clustered into six linkage groups, all showing suppressed or very low recombination in males. Seven markers were sex linked, none of them showing any sign of recombination in males (r=0.00 versus 0.43 on average in females). This opposes classical models of sex chromosome evolution, which envision an initially small differential segment that progressively expands as structural changes accumulate on the Y chromosome. For autosomes, maps were more than 14 times longer in females than in males, which seems the highest ratio documented so far in vertebrates. These results support the pleiotropic model of Haldane and Huxley, according to which recombination is reduced in the heterogametic sex by general modifiers that affect recombination on the whole genome.

Range-Wide Sex-Chromosome Sequence Similarity Supports Occasional XY Recombination in European Tree Frogs (Hyla arborea).

In contrast with mammals and birds, most poikilothermic vertebrates feature structurally undifferentiated sex chromosomes, which may result either from frequent turnovers, or from occasional events of XY recombination. The latter mechanism was recently suggested to be responsible for sex-chromosome homomorphy in European tree frogs (Hyla arborea). However, no single case of male recombination has been identified in large-scale laboratory crosses, and populations from NW Europe consistently display sex-specific allelic frequencies with male-diagnostic alleles, suggesting the absence of recombination in their recent history. To address this apparent paradox, we extended the phylogeographic scope of investigations, by analyzing the sequences of three sex-linked markers throughout the whole species distribution. Refugial populations (southern Balkans and Adriatic coast) show a mix of X and Y alleles in haplotypic networks, and no more within-individual pairwise nucleotide differences in males than in females, testifying to recurrent XY recombination. In contrast, populations of NW Europe, which originated from a recent postglacial expansion, show a clear pattern of XY differentiation; the X and Y gametologs of the sex-linked gene Med15 present different alleles, likely fixed by drift on the front wave of expansions, and kept differentiated since. Our results support the view that sex-chromosome homomorphy in H. arborea is maintained by occasional or historical events of recombination; whether the frequency of these events indeed differs between populations remains to be clarified.

[Archives de la Parole]. , Chanson fantaisiste en mēwātī / [Sir George Grierson], éd. ; Linguistic survey of India ; [Hassaina], voix ; accompagnement instrumental (harmonium indien et tabla)

[Traditions. Asie. Inde. Province de Delhi. Delhi]

[Archives de la Parole]. , Fortune favours the brave : in Bhojpuri of Shahabad (récit, fable) / [Sir George Grierson], éd. ; Linguistic survey of India ; [Hari Sankar Nath], voix

[Traditions. Asie. Inde. Bihar]

[Archives de la Parole]. , The covetous Brahmin [and his reward] : in Oriya - Récit - Indo-Aryen - Ling[uistic] Survey of India / [Sir George Grierson], éd. ; Linguistic survey of India ; [Bepin Chandra Patra], voix

[Traditions. Asie. Inde. Orissa]

[Archives de la Parole]. , Special text in santali / [Sir George Grierson], éd. ; Linguistic survey of India ; Voix parlée, homme

[Traditions. Asie. Inde. Chotā Nāgpur]

[Archives de la Parole]. , A kahani : in Mundari / [Sir George Grierson], éd. ; Linguistic survey of India ; Voix parlée, homme

[Traditions. Asie. Inde. Chotā Nāgpur]

[Archives de la Parole]. , Special text in mundari / [Sir George Grierson], éd. ; Linguistic survey of India ; Voix parlée, homme

[Traditions. Asie. Inde. Chotā Nāgpur]

[Archives de la Parole]. , The Monkey and the Cats : in Bhojpuri of Shahabad / [Sir George Grierson], éd. ; Linguistic survey of India ; [Radha Mohan Prasad Srivastava], voix

[Traditions. Asie. Inde. Bihar]

[Archives de la Parole]. , Parable of the prodigal son : in Nagpuria Bhojpuri / [Sir George Grierson], éd. ; Linguistic survey of India ; [Shiva Sahay Lal], voix

[Traditions. Asie. Inde. Bihar]

[Archives de la Parole]. , La parabole de l'enfant prodigue : Dravidien, Tamoul (groupe de l'Inde péninsulaire, Province de Madras) / [Sir George Grierson], éd. ; Linguistic survey of India ; [Krishnamacharya Ranga Nath], voix

[Traditions. Asie. Inde. Province de Madras [i.e. Chennai]. Etat du Tamil Nadu. Thanjavur]

[Archives de la Parole]. , [Parable of the prodigal son] : récit en tamoul / [Sir George Grierson], éd. ; Linguistic survey of India ; Voix parlée, homme

[Traditions. Asie. Inde. Province de Madras [i.e. Chennai]]

[Archives de la Parole]. , [Parable of the prodigal son] : récit en tamoul / [Sir George Grierson], éd. ; Linguistic survey of India ; Voix parlée, homme

[Traditions. Asie. Inde. Province de Madras [i.e. Chennai]. État du Tamil Nadu]

[Archives de la Parole]. , [Parable of the prodigal son] : récit en télougou / [Sir George Grierson], éd. ; Linguistic survey of India ; Voix parlée, homme

[Traditions. Asie. Inde. Province de Madras [i.e. Chennai]]

[Archives de la Parole]. , [Parable of the prodigal son] : récit tamoul / [Sir George Grierson], éd. ; Linguistic survey of India ; Voix parlée, homme

[Traditions. Asie. Inde. Province de Madras [i.e. Chennai]. Région de Kanara]