Evidence for clonal integration of clones contributing to unexpectedly higher benefits for interspecific neighbours.

Clonal plants benefit from the ability to translocate resources among interconnected ramets to colonize stress habitats. Despite the fact that the physiological integration of clones may influence their general performance and competitiveness, we still lack an understanding of how integration alters the ability of clones to compete with their neighbours. In a greenhouse experiment, we investigated how clonal integration of a perennial herbaceous Cynodon dactylon, which originated from two flooding stress ecotypes, influenced the growth, functional traits, biomass allocation and relative competitiveness of their intraspecific and interspecific neighbours. We also used a greenhouse reciprocal transplant experiment to assess the plasticity and adaptation of clonal integration and test the 'home-field' advantage of clonal integration on the neighbours. The findings showed that, for clones of low-stress ecotypes, clonal integration significantly enhanced the specific root length, biomass storage, root-shoot ratio, and relative competitive ability of the interspecific neighbours, but it had little effect on the overall performance of the intraspecific neighbours across two stress ecotypes. Interestingly, such encouragement also helped the clones expand, suggesting that the clones and their physiologically independent interspecific neighbours can benefit from one another. The home-field advantages of clonal integration were demonstrated by the fact that the clonal ramets from the home site showed more benefit for interspecific neighbours than ramets from the away site. This study provides novel evidence for facilitation and home-field advantage between clones and interspecific neighbours and has implications for understanding stress environments where both high levels of clonality and interspecific facilitation are expected to occur.