Despite their unique adaptations to thrive in canopy environments without access to soil resources, epiphytes are underrepresented in studies of functional traits and of functional composition of tropical plant communities. We investigated functional traits of spermatophytic (seed-bearing) C₃ and CAM epihyte communities in flooded and non-flooded gallery forests in Central Brazil. The two forest types differ in floristic, structure, microclimate and edaphic conditions. We studied plant size, leaf thickness, leaf dry matter content, leaf area, specific leaf area, leaf C, N, P, K, Mg, Ca and C and N stable isotope ratios. Because photosynthetic pathway (C₃ or CAM) is an important aspect of ecologial differentiation of spermatophytic epiphytes, we expected that functional trait syndromes in a multivariate space would be more associated with photosynthetic pathway than forest type and changes in abundance of C₃ and CAM epiphytes would drive functional trait composition at the community level. C₃ and CAM epiphytes segregated in the multivariate trait space, however, more complex functional typologies were also evident. Despite lower light levels, CAM epiphytes were more abundant in the flooded gallery forest. There, they accounted for 80% of all individuals, whereas C₃ epiphytes dominated in the non-flooded forest. These large differences in the proportion of C₃ and CAM epiphytes strongly affected functional trait values at the community level, despite very little intraspecfic variation in trait values between forest types for species that occurred in both forests.  

Field work was carried out in a flooded and a non-flooded gallery forest in the Federal District, in Central Brazil. The flooded gallery forest site (FGF) follows the Taquara/Onça streams (15º55’28” S, 47º54’56” W) and the non-flooded gallery forest site (NFGF) follows the Capetinga stream (15º57’16” S, 47º56’29” W). We collected leaf samples of nine epiphyte species in each gallery forest during the dry season, between July and August of 2018. All individuals were collected close to the main trunk at the lower crown zone (between 7 m and 10 m aboveground), which represents the center zone of the host tree crown. We selected three fully mature, non-senescent leaves of each individual to assess leaf traits. We measured plant size (cm), leaf thickness (mm), leaf area (LA; cm²), specific leaf area (SLA; cm²/g), leaf dry matter content (LDMC; mg/g) and leaf water content (LWC; g/cm²). The average of the three values was used as the trait value for each individual. For elemental analysis, all samples (replicate leaves of each individual combined) were homogenized in a ball mill. Leaf phosphorus (P; %) concentrations were determined following the protocol outlined in Chen et al. (Chen, P.S., Toribara, T.Y., & Warner, H. (1956). Microdetermination of phosphorus. Analytical Chemistry, 28, 1756-1758), while leaf calcium (Ca; %), potassium (K; %) and magnesium (Mg; %) were determined with a flame atomic absorption spectrophotometer AAS240AA (Agilent Technologies, Waldbronn, Germany) after digestion of samples following standard procedures. Leaf carbon (C; %) and nitrogen (N; %), as well as C and N isotope composition (?¹³C and ?¹⁵N; ‰) were determined with a continuous-flow isotope ratio mass spectrometry (IRMS) system.