Resource Use and Morphology of Two Sympatric Japalura Lizards (Iguania: Agamidae)

We investigated the underlying mechanism of coexistence of two sympatric Japalura lizards (Japalura swinhonis and Japalura polygonata xanthostoma). We examined the differences in resource use along three resource dimensions: time, space, and diet. Specifically we tested two ecomorphological hypotheses. Correspondence exists between: perch habitat and limb morphology, and diet and head morphology. The species with shorter forelimbs would perch on narrower surface. The species with larger heads would consume larger or tougher prey. The results showed that the two species did not divide resources by temporal partitioning. Spatially, the two species used similar macrohabitats. However, female J. swinhonis, perching lower and on narrower surfaces, differed from other groups in perch habitats. However, male J. swinhonis and J. p. xanthostoma, despite size and shape differences, were similar in perch habitat. In addition, high diet overlap was detected both intra- and interspecifically despite the presence of significant differences in head sizes. In conclusion, male J. swinhonis and J. p. xanthostoma used largely overlapping resources and therefore, might be potential competitors if resources are limited. We suggest that there was a trade-off between fighting ability and maneuverability because of morphological differences that allowed the coexistence of the two species. Although male J. swinhonis, being larger, may have better fighting ability, J. p. xanthostoma could maneuver around tree trunks and branches to search for prey and avoid fighting more easily.