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Understanding the mechanisms that promote the coexistence of hundreds of species over small areas in tropical forest remains a challenge. Many tropical tree species are presumed to be functionally equivalent shade-tolerant species that differ in performance trade-offs between survival in shade and the ability to quickly grow in sunlight. Variation in plant functional traits related to resource acquisition is thought to predict variation in performance among species, perhaps explaining community assembly across habitats with gradients in resource availability. Many studies have found low predictive power, however, when linking trait measurements to species demographic rates. Seedlings face different challenges recruiting on the forest floor and may exhibit different traits and/or performance trade-offs than older individuals face in the eventual adult niche. Seed mass is the typical proxy for seedling success, but species also differ in cotyledon strategy (reserve vs photosynthetic) or other seedling traits. These can cause species with the same average seed mass to have divergent performance in the same habitat. We combined long-term studies of seedling dynamics with functional trait data collected at a standard developmental stage in three diverse neotropical forests to ask whether variation in coordinated suites of traits predicts variation among species in demographic performance. Across hundreds of species in Ecuador, Panama, and Puerto Rico, we found seedlings displayed correlated suites of leaf, stem, and root traits, which strongly correlated with seed mass and cotyledon strategy. Variation among species in seedling functional traits, seed mass, and cotyledon strategy were strong predictors of trade-offs in seedling growth and survival. Our findings highlight the importance of cotyledon strategy in addition to seed mass as a key component of seed and seedling biology. These results also underscore the importance of matching the ontogenetic stage of the trait measurement to the stage of demographic dynamics. Synthesis: With strikingly consistent patterns across three tropical forests, we find strong evidence for the promise of functional traits to provide mechanistic links between seedling form and demographic performance.
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This content will become publicly available on December 17, 2026
Chewing performance and the structure of primate communities
Ecomorphological theory predicts a relationship between the morphology of a given trait and its ecological performance. In turn, variation in ecomorphology is viewed as integral to the structuring of animal communities. This reasoning is practically axiomatic, but the full logic chain is seldom integrated into a single study. We tested the functional relationship between premolar tooth size and chewing performance across a diverse community of wild primates, including chimpanzees and seven monkey species. We found that relatively large premolars were associated with improved food fracture, and that the chewing performance of granivores (seed predators) exceeded that of sympatric folivores and frugivores by 51–56% and 64–68%, respectively. This finding is robust when controlling for variation in chewing effort and seasonal grit ingestion. Evidence of convergent evolution speaks to the fitness advantages of enlarged premolars among granivorous species, and we show that premolar-mediated seed-eating shapes the composition of primate communities across nine African forest sites. Our findings are relevant to palaeoanthropology and the puzzling megadontia of some fossil hominin lineages, as our data favour a diet of stress-limited brittle foods, not ductile foods, as the principal selective pressure favouring the performance benefits of enlarged premolars.
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- Award ID(s):
- 2316561
- PAR ID:
- 10655035
- Publisher / Repository:
- The Royal Society
- Date Published:
- Journal Name:
- Proceedings of the Royal Society of London Series B Biological sciences
- ISSN:
- 0080-4649
- Subject(s) / Keyword(s):
- chewing performance, primate feeding ecology, siliceous particulate matter, Paranthropus
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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