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Abstract While natural communities can contain hundreds of species, modern coexistence theory focuses primarily on species pairs. Alternatively, the structural stability approach considers the feasibility of equilibria, gaining scalability to larger communities but sacrificing information about dynamic stability. Three‐species competitive communities are a bridge to more‐diverse communities. They display novel phenomena while remaining amenable to mathematical analysis, but remain incompletely understood. Here, we combine these approaches to identify the key quantities that determine three‐species competition outcomes. We show that pairwise niche overlap and fitness differences are insufficient to completely characterize competitive outcomes, which requires a strictly triplet‐wise quantity: cyclic asymmetry, which underlies intransitivity. Low pairwise niche overlap stabilizes the triplet, while high fitness differences promote competitive exclusion. The effect of cyclic asymmetry on stability is complex and depends on pairwise niche overlap. In summary, we elucidate how pairwise niche overlap, fitness differences and cyclic asymmetry determine three‐species competition outcomes.
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Niche expansion via acquired metabolism facilitates competitive dominance in planktonic communities
Abstract Acquired phototrophs, organisms that obtain their photosynthetic abilities by hosting endosymbionts or stealing plastids from their prey, are omnipresent in aquatic ecosystems. This acquisition of photosynthetic metabolism allows for niche expansion, and can therefore influence competition outcomes by alleviating competition for shared resources. Here, we test how acquired metabolism alters competitive outcomes by manipulating light availability to control the energetic contribution of photosynthesis to acquired phototrophs. Using freshwater protists that compete for bacterial prey, we demonstrate light‐dependent competition outcomes of acquired phototrophs ( Paramecium bursaria ) and strict heterotrophs ( Colpidium sp.) in laboratory model experiments. We then synthesize these findings using a series of mathematical models, and show that explicitly accounting for resource competition improves model fits. Both empirical and mathematical models predict that the acquired phototroph should increase in competitive dominance with increasing light availability. Our results highlight the importance of acquired metabolism to community dynamics, highlighting the need for more empirical and theoretical studies of this mechanism for niche expansion.
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- Award ID(s):
- 1851194
- PAR ID:
- 10446614
- Date Published:
- Journal Name:
- Ecology
- Volume:
- 103
- Issue:
- 7
- ISSN:
- 0012-9658
- 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/10.1002/ecy.3693
