Evolution of zinc finger-Y and zinc finger-X genes in oryzomyne-akodontine rodents (Cricetidae)

Zinc finger-Y (Zfy) and zinc finger-X (Zfx) genes were analyzed by Southern blotting in male and female specimens of 10 species belonging to the oryzomyne-akodontine stock of Cricetidae rodents. DNA fragments were used as characters to construct a parsimony tree of the genes. Zfx and Zfy trees in general coincide with the evolutionary history of the taxa. Both trees show Oryzomys longicaudatus genes as the outgroup whereas Akodon xanthorrhinus genes are also distant from those of the other species. Oxymycterus rufus and Bolomys obscurus share related sequences, while genes from the other six Akodon species form a group of their own. It was found that 9 out of the 10 species analyzed show Zfy amplification in a range varying from 2 to 24 copies and with a pattern that is clade specific. The estimation of the average changes per character strongly suggests that Zfy has evolved more rapidly than Zfx; our estimates of the rate of nucleotide substitution are 4.6 times higher for Zfy than for Zfx.