Biotic homogenization is a ubiquitous consequence of human disturbance. Through a mix of local extinctions and invasions, diverse communities of specialists are often replaced by or inundated with generalist species, resulting in uncertain consequences for ecological functions. While concern about biotic homogenization is growing, intraspecific variation and individual diet specialization (IS) have also emerged as key drivers of ecological functions. The niche variation hypothesis predicts that when a population is released from interspecific competition (ie “ecological release”), intraspecific competition will promote resource niche expansion and IS. It then follows that if biotic homogenization reduces taxonomic diversity and
Intraspecific variation, including individual diet variation, can structure populations and communities, but the causes and consequences of individual foraging strategies are often unclear. Interactions between competition and resources are thought to dictate foraging strategies (e.g. specialization vs. generalization), but classical paradigms such as optimal foraging and niche theory offer contrasting predictions for individual consumers. Furthermore, both paradigms assume that individual foraging strategies maximize fitness, yet this prediction is rarely tested. We used repeated stable isotope measurements (δ13C, δ15N; Consistent with niche theory, individuals contracted their trophic niches and increased foraging specialization in response to both intraspecific and interspecific competition, but this effect was offset by resource availability and individuals generalized when plant biomass was high. Nevertheless, individual specialists obtained no apparent fitness benefit from trophic niche contractions as the most specialized individuals exhibited a 10% reduction in monthly survival compared to the most generalized individuals. Ultimately, this resulted in annual survival probabilities nearly 4× higher for generalists compared to specialists. These results indicate that competition is the proximate driver of individual foraging strategies, and that diet‐mediated fitness variation regulates population and community dynamics in stochastic resource environments. Furthermore, our findings show dietary generalism is a fitness maximizing strategy, suggesting that plastic foraging strategies may play a key role in species' ability to cope with environmental change.
- Award ID(s):
- 1655499
- NSF-PAR ID:
- 10446880
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Journal of Animal Ecology
- Volume:
- 90
- Issue:
- 12
- ISSN:
- 0021-8790
- Page Range / eLocation ID:
- p. 2806-2818
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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