Trait acclimation of the clonal fern Selliguea griffithiana to forest epiphytic and terrestrial habitats

Although epiphytic habitats are more stressful and heterogeneous than terrestrial habitats, how facultative epiphytes acclimate to such contrasting environments has been poorly understood. Our study focused on the variation of functional traits between epiphytic and terrestrial individuals of Selliguea griffithiana, and provided considerable functional acclimation of this species to such contrasting environments. We sampled ramets of S. griffithiana from epiphytic and terrestrial habitats of a subtropical montane moist forest, SW China. Morphological and anatomical traits, photosynthesis, biomass and ramet density of S. griffithiana were measured and it was found that these traits differed significantly between the two habitats. Frond length, stipe length, spacer length (interramet distance), stomatal density, vein density, maximal chlorophyll fluorescence and relative chlorophyll content of fronds, and biomass per ramet were all lower in epiphytic habitat than those in terrestrial habitat, whereas frond thickness and ramet density were higher in the former. Photosynthetic light-response curves revealed a higher carbon assimilation capability of individuals in terrestrial habitat than in epiphytic habitat, whereas cumulative water loss curves showed a lower water loss rate in the latter. The findings demonstrate acclimation of S. griffithiana to both habitats, that is, epiphytic ramets can mitigate water scarcity at some cost of a reduced photosynthetic capacity, whereas terrestrial ramets can afford to improve the light capture to a higher photosynthetic capacity without any water stresses.