Non-omnivorous generality promotes population stability

Using a combination of stable isotope analysis of δ¹³C and δ¹⁵N and long-term census data on population abundances for meiofauna in tropical aquatic rock pools, we provide evidence that species which exhibit greater variation in δ¹³C, an indication of a greater range of distinct carbon sources in their diet, have more stable populations than species with lower variation in δ¹³C. This link between increased isotope variability and reduced population variability, however, did not hold for δ¹⁵N. This suggests that increases in population stability were due to non-omnivorous feeding on multiple carbon sources within a trophic level rather than omnivorous feeding on multiple carbon sources across trophic levels. Our findings corroborate MacArthur's original hypothesis that populations that can access a greater range of resources are more stable than those which consume a more restricted range of resources.