Different “metabolomic niches” of the highly diverse tree species of the French Guiana rainforests

Albert Gargallo-Garriga , Jordi Sardans , Victor Granda , Joan Llusià , Guille Peguero , Dolores Asensio , Romà Ogaya , Ifigenia Urbina , Leandro van Langenhove , Lore Verryckt , Jérôme Chave (1) , Elodie A Courtois (2) , Clément Stahl (3) , Oriol Grau , Karel Klem , Otmar Urban , Ivan Janssens , Josep Peñuelas

1 EDB - Evolution et Diversité Biologique
2 LEEISA - Laboratoire Ecologie, Evolution, Interactions des Systèmes amazoniens
3 UMR ECOFOG - Ecologie des forêts de Guyane

Tropical rainforests harbor a particularly high plant diversity. We hypothesize that potential causes underlying this high diversity should be linked to distinct overall functionality (defense and growth allocation, anti-stress mechanisms, reproduction) among the different sympatric taxa. In this study we tested the hypothesis of the existence of a metabolomic niche related to a species-specific differential use and allocation of metabolites. We tested this hypothesis by comparing leaf metabolomic profiles of 54 species in two rainforests of French Guiana. Species identity explained most of the variation in the metabolome, with a species-specific metabolomic profile across dry and wet seasons. In addition to this "homeostatic" species-specific metabolomic profile significantly linked to phylogenetic distances, also part of the variance (flexibility) of the metabolomic profile was explained by season within a single species. Our results support the hypothesis of the high diversity in tropical forest being related to a species-specific metabolomic niche and highlight ecometabolomics as a tool to identify this species functional diversity related and consistent with the ecological niche theory. Tropical rainforests are characterized by amazingly high species diversity 1-3. Numerous mechanisms have been proposed to explain the origin and the maintenance of such high tropical tree species coexistence on local scales 3,4. Several factors such as soil heterogeneity 2,5 , micro-site singularities 6 , gradients of soil nutrient availability 2,7-9 , patchy distribution of the soil traits 10,11 , slope 12 , heterogeneity of disturbances and regeneration regimes 1 , topography 13 , or the long-term divergence of species-specific defences against herbivores 14 have been identified as promoters of species coexistence and the maintenance of tree diversity in the tropics. The concept of the Hutchinson multidimensional niche 15 is a central theory used to explain species coexistence and shape communities composition, diversity and structure in ecological studies. The study and quantifica-tion of species niche at different spatial scales has been used to understand the functional diversity and ecological strategies of different species 16. The classical way to estimate this functional niche is to focus on morphological and functional traits linked to the species strategy that are easier to measure in the field conditions (such as specific leaf area, foliar toughness, …). Numerous studies have combined this conceptual framework with functional foliar traits measurements to explain species coexistence, niche overlap level and thus the competition intensity 17-24. The metabolomic profile of a particular species results from the phenotypical expression of the species-specific combination of functional traits. Thus, by downscaling the "functional niche" theory to the molecular level, we here reduce the "niche" to the "metabolomic niche". In a molecular approach each species should adjust its metabolome to ensure optimized biochemical and physiological functions at the homeostatic state given a certain amount of resources. In addition to this "homeostatic" species-specific metabolomic niche, each species should,

Domaines: Ecologie, Environnement

Albert Gargallo-Garriga, Jordi Sardans, Victor Granda, Joan Llusià, Guille Peguero, et al.. Different “metabolomic niches” of the highly diverse tree species of the French Guiana rainforests. Scientific Reports, 2020, 10 (1), ⟨10.1038/s41598-020-63891-y⟩. ⟨hal-03006005⟩