We studied how individuals modify their behavior in response to inter- and intraspecific competitors and how these changes affected the pattern of variation between populations and species. As study models, we used tadpoles of two brown frogs, Rana latastei and R. dalmatina . Since R. latastei is always sympatric to R. dalmatina , whereas R. dalmatina is sympatric to R. latastei only in the periphery of its range, we predicted...