Trophic niche divergence reduces survival in an omnivorous rodent

Hypothesis: Individuals that diverge from their population's mean trophic niche suffer reduced survival. Organism: The Taiwan field mouse, Apodemus semotus, a common, small, omnivorous rodent. Field site: Pinus-Alnus-Quercus forest in central Taiwan (121°18E, 24°21N). Methods: We used capture-recapture data to measure the survival of individual Apodemus semotus. We measured individual trophic niches using stable carbon and nitrogen isotope values obtained from samples of the rodents' hair. We used stepwise logistic regression to evaluate whether an individual's survival depended on the divergence of its trophic niche from the population mean. We controlled for the potentially confounding effects of resource abundance with dry weights of seeds and arthropods collected in seed traps and pitfall traps. Conclusions: The probability of survival declined with increasing niche divergence from the population mean. Stabilizing selection in this population of Apodemus semotus is thus acting to conserve niche width and location.