Browsing by Autor "Nathan Muchhala"

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Chemical properties of foliar metabolomes represent a key axis of functional trait variation in forests of the tropical Andes
(Royal Society, 2026) Sierra Chadwick; David Henderson; Arden Perkins; Leslie Cayola; Alfredo Fuentes; Belen Alvestegui; Nathan Muchhala; J. Sebastián Tello; Martin Volf; J. Wilson Myers
Plants interact with their environment through diverse specialized metabolites that protect them from abiotic stressors, like drought or radiation, and biotic stressors, like herbivores or pathogens. However, few studies have considered the chemical properties of metabolites as a potential axis of functional trait variation along environmental gradients. Here, we examined how the chemical properties of foliar metabolomes, such as mean aromaticity, hydrophobicity and polarity, as well as commonly used morphological traits, vary with climate and elevation among 16 forest plots in the tropical Andes of Bolivia. We found that chemical properties were weakly related to morphological traits among tree species, yet both varied significantly with climate and elevation. In particular, abundance-weighted mean hydrophobicity decreased, and polar surface area increased with elevation and in colder and drier climates. Additionally, co-occurring species showed increasing chemical similarity with elevation for the most-aromatic and most-polar metabolites. These results suggest that abiotic stress associated with colder, drier climates and solar radiation acts as a filter for metabolome chemical properties. This contrasts with chemical dissimilarity observed at lower elevations, which is likely driven by pressure from host-specialized enemies in warmer, wetter climates. Our results introduce the possibility that chemical defences may be constrained by abiotic stressors.
Ecological metabolomics of tropical tree communities across an elevational gradient: Implications for chemically-mediated biotic interactions and species diversity
(2023) D. Henderson; Brian E. Sedio; J. Sebastián Tello; Leslie Cayola; A C.; Belen Alvestegui; Nathan Muchhala; Jonathan A. Myers
Abstract Seminal hypotheses in ecology and evolution postulate that stronger and more specialized biotic interactions contribute to higher species diversity at lower elevations and latitudes. Plant-chemical defenses mediate biotic interactions between plants and their natural enemies and provide a highly dimensional trait space in which chemically mediated niches may facilitate plant species coexistence. However, the role of chemically mediated biotic interactions in shaping plant communities remains largely untested across large-scale ecological gradients. To test this hypothesis, we used ecological metabolomics to quantify the chemical dissimilarity of foliar metabolomes among 473 tree species (906 unique species-plot combinations) in 16 tropical tree communities along an elevational gradient in Madidi National Park, Bolivia. We predicted that chemical dissimilarity among co-occurring tree species would be greater, and chemical phylogenetic signal lower, in communities with greater tree species richness and warmer, wetter, and less-seasonal climates, as pressure from natural enemies is likely to be greater in these locales. Further, we predicted that these relationships should be especially pronounced for secondary metabolites derived from biosynthetic pathways known to include anti-herbivore and antimicrobial defenses than for primary metabolites. We found that median chemical dissimilarity among tree species with respect to all metabolites and secondary metabolites increased with tree species richness, decreased with elevation, and increased along a principal component of climatic variation that reflected increasing temperature and precipitation and decreasing seasonality. In contrast, median chemical dissimilarity among tree species with respect to primary metabolites was unrelated to tree species richness, elevation, or the principal component of climatic variation. Furthermore, phylogenetic signal of secondary and primary metabolites decreased with tree species richness. Among tree communities in moist forests, phylogenetic signal of secondary metabolites also increased with elevation and decreased with the temperature and precipitation. Our results support the hypothesis that chemically mediated biotic interactions shape elevational diversity gradients by imposing stronger selection for interspecific divergence in plant chemical defenses in warmer, wetter, and more stable climates. Our study also illustrates the promise of ecological metabolomics in the study of biogeography, community ecology, and complex species interactions in high-diversity ecosystems.
Testing the role of biotic interactions in shaping elevational diversity gradients: An ecological metabolomics approach
(Wiley, 2025) D. Henderson; J. Sebastián Tello; Leslie Cayola; A C.; Belen Alvestegui; Nathan Muchhala; Brian E. Sedio; Jonathan A. Myers
Seminal hypotheses in ecology and evolution postulate that stronger and more specialized biotic interactions contribute to higher species diversity at lower elevations and latitudes. Plant-chemical defenses mediate biotic interactions between plants and their natural enemies and provide a highly dimensional trait space in which chemically mediated niches may facilitate plant species coexistence. However, the role of chemically mediated biotic interactions in shaping plant communities remains largely untested across large-scale ecological gradients. Here, we used ecological metabolomics to quantify the chemical dissimilarity of foliar metabolomes among 473 tree species in 16 tropical tree communities along an elevational gradient in the Bolivian Andes. We predicted that tree species diversity would be higher in communities and climates where co-occurring tree species are more chemically dissimilar and exhibit faster evolution of secondary metabolites (lower chemical phylogenetic signal). Further, we predicted that these relationships should be especially pronounced for secondary metabolites known to include antiherbivore and antimicrobial defenses relative to primary metabolites. Using structural equation models, we quantified the direct effects of rarefied median chemical dissimilarity and chemical phylogenetic signal on tree species diversity, as well as the indirect effects of climate. We found that chemical dissimilarity among tree species with respect to all metabolites and secondary metabolites had positive direct effects on tree species diversity, and that climate (higher temperature and precipitation, and lower temperature seasonality) had positive indirect effects on species diversity by increasing chemical dissimilarity. In contrast, chemical dissimilarity of primary metabolites was unrelated to species diversity and climate. Chemical phylogenetic signal of all metabolite classes had negative direct effects on tree species diversity, indicating faster evolution of metabolites in more diverse communities. Climate had a direct effect on species diversity but did not indirectly affect diversity through chemical phylogenetic signal. Our results support the hypothesis that chemically mediated biotic interactions shape elevational diversity gradients by imposing stronger selection for chemical divergence in more diverse communities and maintaining higher chemical dissimilarity among species in warmer, wetter, and more stable climates. Our study also illustrates the promise of ecological metabolomics in the study of biogeography, community ecology, and complex species interactions in high-diversity ecosystems.