My dissertation research will focus on the costs and benefits of spatial segregation in two closely related species of treefrogs (Hyla chrysoscelis and Hyla versicolor).  The calls of H. chrysoscelis have a pulse rate that is twice as fast as the calls of H. versicolor.  Pulse rate is an important call property for species recognition, and females of both species exhibit robust preferences for calls with pulse rates equal to that of their own species.  Mating with the wrong species is very costly, resulting in hybrids with decreased fitness.  Both H. chrysoscelis and H. versicolor occur throughout the U.S. in both allopatry and sympatry.  In allopatric populations, males of both species call from similar locations within the habitat of a breeding pond.  However, in sympatric populations, males exhibit consistent patterns of spatial segregation:  H. chrysoscelis typically calls from sparse vegetation in open water, whereas H. versicolor typically calls from elevated perches in dense vegetation surrounding the edge of the pond.  While signaling in different habitats benefits signalers and receivers by reducing the negative effects of interference from other species’ calls, spatial segregation may also incur costs of its own in the form of signal degradation.  Microhabitat differences in vegetation structure and substrate characteristics can cause acoustic signals to degrade differently.  In addition, signals that differ in their temporal and spectral properties also differ in their susceptibility to habitat-induced degradation .  I will investigate whether the directional patterns of spatial segregation exhibited by H. chrysoscelis and H. versicolor are due to species differences in susceptibility to habitat-induced signal degradation.