Nutrient foraging in woodland herbs: a comparison of three species of Uvularia (Liliaceae) with contrasting belowground morphologies

We compared the ability of three closely related species, Uvularia perfoliata, U. sessilifolia, and U. puberula, to forage and explore patches in nutritionally homogeneous and heterogeneous environments. The species differed in type and function of plagiotropic stems and the extent of clonality and physiological integration. Our aim was to determine (1) whether selective placement of roots in high-nutrient patches, i.e., foraging, was accompanied by facilitatory morphological changes such as internode elongation or increased branching, (2) whether foraging ability of species depended on the extent of physiological integration, and (3) how variability in environmental quality influenced the performance of each species. We studied the growth of each species over two seasons in experimental environments. Uvularia perfoliata and U. puberula foraged in highnutrient patches in heterogeneous environments. Uvularia sessilifolia did not show selective placement of roots. The two clonal species, U. perfoliata and U. sessilifolia, did not show any changes in architectural traits predicted to facilitate foraging. The nonclonal species, U. puberula, was the strongest forager and the most physiologically integrated species, U. sessilifolia, was the weakest forager, in line with the view that physiological integration limits foraging efficiency. Variability in environmental quality had little effect on the performance of the three species. Yield and estimators of fitness were not greater in treatments where more high-quality patches were encountered consecutively than in treatments where fewer high-quality patches were encountered consecutively during growth.