Figure 22.2 Cryptic Species Look Alike but Do Not Interbreed These two species of gray tree frogs cannot be distinguished by their external morphology, but they do not interbreed even when they occupy the same geographic range. (A) Hyla versicolor is a tetraploid species (four sets of chromosomes), whereas (B) H. chrysoscelis is diploid (two sets of chromosomes). And although they look alike, the males have distinctive mating calls; female frogs recognize and mate with males of their own species based on these calls.