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Changes of consumers’ trophic niches, the n-dimensional biotic space that allows a species to satisfy its minimum requirements for population growth, are driven in part by shifts in the degree of individual resource use specialization within a population. Individual specialization results from complex trade-offs in inter- and intraspecific competition as organisms reduce niche overlap within a population or with heterospecifics. It is vital to build empirical knowledge on the trophic niche dynamics of consumers, given the role that niche dynamics play in food web stability, species coexistence, and population resilience, especially quantifying the trophic niche’s expansion and contraction of coastal fish populations experiencing increasing frequency of environmental disturbance and habitat transformation. In coastal ecosystems, disturbances alter the connectivity, productivity, and nutrient regimes of aquatic habitats, which could lead to significant shifts in consumers’ trophic niches. We investigated the trophic niche dynamics of two fish species Centropomus undecimalis (Common Snook) and Megalops atlanticus (Atlantic Tarpon), across two adjacent coastal lake systems of varying nutrient regimes (eutrophic vs. mesotrophic) and hydrological connectivity. In both systems, Snook had larger trophic niches than Tarpon. Also, the trophic niche size in the eutrophic system was larger than the mesotrophic system for both species. Snook and Tarpon used different prey resources, resulting in low niche overlap between species in both systems. Our results highlight how altered hydrological connectivity, and nutrient regimes can shift trophic niche dynamics of higher trophic-level consumers, likely due to changes in prey landscapes and shifts in the foraging ecology of species.
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Spatial ecology of territorial populations
Many ecosystems, from vegetation to biofilms, are composed of territorial populations that compete for both nutrients and physical space. What are the implications of such spatial organization for biodiversity? To address this question, we developed and analyzed a model of territorial resource competition. In the model, all species obey trade-offs inspired by biophysical constraints on metabolism; the species occupy nonoverlapping territories, while nutrients diffuse in space. We find that the nutrient diffusion time is an important control parameter for both biodiversity and the timescale of population dynamics. Interestingly, fast nutrient diffusion allows the populations of some species to fluctuate to zero, leading to extinctions. Moreover, territorial competition spontaneously gives rise to both multistability and the Allee effect (in which a minimum population is required for survival), so that small perturbations can have major ecological effects. While the assumption of trade-offs allows for the coexistence of more species than the number of nutrients—thus violating the principle of competitive exclusion—overall biodiversity is curbed by the domination of “oligotroph” species. Importantly, in contrast to well-mixed models, spatial structure renders diversity robust to inequalities in metabolic trade-offs. Our results suggest that territorial ecosystems can display high biodiversity and rich dynamics simply due to competition for resources in a spatial community.
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- Award ID(s):
- 1734030
- PAR ID:
- 10169865
- Date Published:
- Journal Name:
- Proceedings of the National Academy of Sciences
- Volume:
- 116
- Issue:
- 36
- ISSN:
- 0027-8424
- Page Range / eLocation ID:
- 17874 to 17879
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1073/pnas.1911570116
