Allozyme and advertisement call variation in the tungara frog, Physalaemus pustulosus

Abstract

We analyzed variation in advertisement calls and allozymes in 30 populations along a 5000-km transect throughout most of the range of the tungara frog, Physalaemus pustulosus. All 12 call variables measured show significant differences among populations despite the importance of the advertisement call in species recognition. Some call variables exhibited clinal variation, whereas most others differed between the two major allozyme groups that have invaded Panama at different times, perhaps 4-4.5 million yr apart. Call variables that primarily affect discrimination among conspecifics tended to exhibit greater variation than call variables thai are crucial for species recognition. The proximate mechanism of production underlying a call variable, however, is a better predictor of its variation. Contrary to predictions of some sexual selection models, call variation exhibits predictable patterns of geographical variation, although a substantial portion of variation among populations is not explained by geographic position. Although allozymes, calls, and geography usually covary, closer populations can have more similar calls independent of allozyme similarity.