The effects of intra- and inter-specific competitions on personality and individual plasticity in two sympatric brown frogs

By adopting a multi-hierarchical approach, we study how among-population and among-species differences in the strength of intra- and inter-specific competition affect the individual flexible responses to competitors. 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 a stronger response to heterospecifics in R. latastei than in R. dalmatina and, within each species, in syntopic than in allotopic populations. To test these predictions, we raised tadpoles, from either syntopic or allotopic populations, either in syntopy or allotopy and repeatedly tested them in open field trials in the presence of a caged conspecific, a caged heterospecific or an empty cage. As predicted, we found that R. latastei tadpoles were more flexible than R. dalmatina tadpoles and that flexibility was higher in syntopic than in allotopic populations. In both species, flexibility at the species level was consistent with that at the individual level either because there were no among-individual differences (no “personality” effect) or because differences were consistent across contexts (positive across-context correlations). Besides these differences in flexibility, however, the two species also showed unpredicted and context-independent behavioral differences, suggesting that there might be more to interspecific variation in flexibility than the effect of selection by heterospecific competitors.