Ecophysiological and anatomical variation in Setaria parviflora (Poaceae) between contrasting environments in the Brazilian Cerrado

Environmental heterogeneity can be associated with substantial phenotypic variation in plant populations, but the integration of ecophysiological and anatomical variation under natural field conditions remains poorly understood for many tropical grasses. Setaria parviflora is a perennial C 4 grass occurring in contrasting environments of the Brazilian Cerrado. We compared ecophysiological and anatomical traits of populations from a preserved palm swamp and an adjacent dry disturbed area. Net CO₂ assimilation, water-use efficiency, and instantaneous carboxylation efficiency were higher in plants from the dry disturbed area, whereas stomatal conductance, transpiration, relative water content, and specific leaf area did not differ between populations. Root aerenchyma area and vascular cylinder area were greater in individuals from the palm swamp, whereas the number of xylem poles was greater in the dry disturbed area. Culm vessel element area was greater in the dry disturbed area, whereas abaxial stomatal density was higher in the palm swamp. Principal component analyses showed clearer differentiation between populations for physiological than for anatomical traits, while the environmental PCA summarized the distinct field conditions recorded during the two sampling campaigns. Together, these results show that anatomical and ecophysiological traits vary differently between natural populations of S. parviflora under contrasting local conditions, highlighting the value of integrating structural and functional traits when assessing phenotypic variation in field populations.