Consequences of intraspecific niche variation: phenotypic similarity increases competition among recently metamorphosed frogs

• Published in: Oecologia 2011-07, Vol.166 (3), p.585-592
• Main Authors: Benard, Michael F., Maher, Jessica Middlemis
• Format: Article
• Language: English
• Subjects: Amphibia. Reptilia; Amphibians; Animal and plant ecology; Animal, plant and microbial ecology; Animals; Biological and medical sciences; Biomedical and Life Sciences; Body Size; Competition (Economics); Diet; Ecological competition; Ecological genetics; Ecology; Ecosystem; Experimental design; Food Chain; Frogs; Fundamental and applied biological sciences. Psychology; General aspects; Genetic variation; Growth rate; Hydrology/Water Resources; Life Sciences; Metamorphosis; Metamorphosis, Biological; Michigan; Niches; Phenotype; Phenotypic variation; Phenotypic variations; Plant Sciences; Population ecology; Population ecology - Original Paper; Population growth; Predatory Behavior; Rana sylvatica; Ranidae - growth & development; Ranidae - physiology; Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution
• ISSN: 0029-8549; 1432-1939
• DOI: 10.1007/s00442-010-1896-6

Phenotype is often correlated with resource use, which suggests that as phenotypic variation in a population increases, intraspecific competition will decrease. However, few studies have experimentally tested the prediction that increased intraspecific phenotypic variation leads to reduced competitive effects (e.g., on growth rate, survival or reproductive rate). We investigated this prediction with two experiments on wood frogs (Rana sylvatica). In the first experiment, we found that a frog's size was positively correlated with the size of its preferred prey, indicating that the feeding niche of the frogs changed with size. In the second experiment, we used an experimental design in which we held the initial mass of "focal" frogs constant, but varied the initial mass of their competitors. We found a significant quadratic effect of the average mass of competitors: focal frog growth was lowest when raised with similar-sized competitors, and highest when raised with competitors that were larger or smaller. Our results demonstrate that growth rates increase (i.e., competitive intensity decreases) when individuals are less similar to other members of the population and exhibit less overlap in resource use. Thus, changes in the amount of phenotypic variation in a population may ultimately affect population-level processes, such as population growth rate and extinction risk.