Clonal integration enhances expansion ability of Ipomoea aquatica in aquatic–terrestrial ecotones

Abstract

Clonal integration has been repeatedly shown to promote the performance of clonal plants in both terrestrial and aquatic heterogeneous habitats. However, only a few studies have explicitly tested the effect of clonal integration in aquatic–terrestrial ecotones. To test the role of clonal integration in aquatic–terrestrial ecotones, we conducted an experiment with an amphibious, stoloniferous clonal plant Ipomoea aquatica, where apical parts of stolon fragments of I. aquatica were planted in water and basal parts were in soil. Stolon connection between apical and basal parts was either left intact (i.e., the maintenance of clonal integration) or severed (i.e., the loss of clonal integration). We also set up three different nitrogen levels in water to further test the effect of increased water nitrogen on the outcome of clonal integration. Results indicated that clonal integration could facilitate the establishment of apical parts of I. aquatica in aquatic areas at no costs to interconnected basal ramets in terrestrial areas, and also improve the performance of basal parts at the medium- and high-nitrogen level. Besides, the maintenance of stolon connection could greatly promote the fitness of whole fragments of I. aquatica, irrespective of water nitrogen level. Therefore, clonal integration may be an important life history trait that contributes to the expansion of I. aquatica in aquatic–terrestrial ecotones.