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.
Berset-Brändli
Laura
L
Department of Ecology and Evolution, University of Lausanne, 1015 Lausanne, Switzerland.
Jaquiéry
Julie
J
Broquet
Thomas
T
Ulrich
Yuko
Y
Perrin
Nicolas
N
D000818:Animals; D001001:Anura / Q000235:genetics*; D002874:Chromosome Mapping; D017931:DNA Primers / Q000235:genetics; D005260:Female; D014644:Genetic Variation; D008297:Male; D018895:Microsatellite Repeats / Q000235:genetics; D008957:Models, Genetic; D011995:Recombination, Genetic / Q000235:genetics*; D012730:Sex Chromosomes / Q000235:genetics*; D012737:Sex Factors; D013557:Switzerland
D017931:DNA Primers