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The eastern green tree frog looks exactly like the close related cops gree tree frog, the big difference between the two species is beneath the surface. The eastern has twice the number of chromosomes² as those of the cops. Having more size of chromosomes makes the cells of eastern frog larger than the cells found in the cops, and those bigger cells make the eastern's sound just a little deeper. Now University of Missouri researcher Crow G. and a student Mickey Tarker have determine that the slight difference in the calls here is the eastern again. And here is the cops. Is that the females know which species males * with the ones was the same chromosome¹ number that they have. The work is in the Proceedings³ of the Royal Society B Biological Sciences. Speciation is often caused by a geographic⁴ barrier that keeps population from mating, but the tree frog situation maybe a rare case in which chromosome duplication and * presented a reproductive barrier. As a new man it comes down to wether they calls.

Thanks for the minute of Scientific American's sixty seconds science, I'm Steve Mirsky. 

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