Soil nutrient-related trait variation in Leiothrix (Eriocaulaceae) species from Brazilian rock outcrops

Abstract

Campos rupestres are shaped by nutrient limitation and strong heterogeneity, traditionally interpreted within a phosphorus-centered framework. We evaluated how soil nutrient variation relates to plant morphology and biomass allocation in three endemic Leiothrix (Eriocaulaceae) species inhabiting campos rupestres of the Serra do Cipó, Brazil. Using linear mixed-effects models, we investigated relationships between vegetative traits, ramet biomass partitioning, and soil nutrient concentrations. Soil nutrient effects were species- and trait-specific. In L. crassifolia, Fe showed predominantly negative associations with plant and leaf dimensions. Cu, B, and K were positively associated with vegetative growth and biomass traits. Zn negatively affected root biomass and belowground allocation. Leiothrix spiralis exhibited intermediate responsiveness, with Fe positively associated with leaf traits and Zn and Mn showing negative relationships. Leiothrix mucronata displayed limited responsiveness, with nutrient effects restricted mainly to belowground traits. Leiothrix crassifolia showed high responsiveness, whereas L. mucronata exhibited the weakest responses. These contrasting patterns reveal substantial interspecific variation in soil nutrient responsiveness within a single genus and suggest that specific soil nutrients are associated with functional differentiation among closely related species. Our findings highlight the importance of considering multiple soil nutrients to better understand plant–soil interactions and trait variation in oligotrophic rock outcrop ecosystems.