Abstract
Many notorious invasive plants are clonal, however, little is known about the different roles of clonal integration effects between invasive and native plants. Here, we hypothesize that clonal integration affect growth, photosynthetic performance, biomass allocation and thus competitive ability of invasive and native clonal plants, and invasive clonal plants benefit from clonal integration more than co-occurring native plants in heterogeneous habitats. To test these hypotheses, two stoloniferous clonal plants, Alternanthera philoxeroides (invasive), Jussiaea repens (native) were studied in China. The apical parts of both species were grown either with or without neighboring vegetation and the basal parts without competitors were in nutrient- rich or -poor habitats, with stolon connections were either severed or kept intact. Competition significantly reduced growth and photosynthetic performance of the apical ramets in both species, but not the biomass of neighboring vegetation. Without competition, clonal integration greatly improved the growth and photosynthetic performance of both species, especially when the basal parts were in nutrient-rich habitats. When grown with neighboring vegetation, growth of J. repens and photosynthetic performance of both species were significantly enhanced by clonal integration with the basal parts in both nutrient-rich and -poor habitats, while growth and relative neighbor effect (RNE) of A. philoxeroides were greatly improved by clonal integration only when the basal parts were in nutrient-rich habitats. Moreover, clonal integration increased A. philoxeroides's biomass allocation to roots without competition, but decreased it with competition, especially when the basal ramets were in nutrient-rich sections. Effects of clonal integration on biomass allocation of J. repens was similar to that of A. philoxeroides but with less significance. These results supported our hypothesis that invasive clonal plants A. philoxeroides benefits from clonal integration more than co-occurring native J. repens, suggesting that the invasiveness of A. philoxeroides may be closely related to clonal integration in heterogeneous environments.
Highlights
Clonal integration, through which connected ramets of clonal plants can share water, carbohydrates,nutrients and other substances such as pollutants, diseases, etc. [1,2,3], may improve plants’ exploitation of ubiquitous heterogeneous resources, help plants invade new environments and facilitate plants’ spatial occupation of new habitats at a local scale [4]
Growth and the relative neighbor effect (RNE) Integration treatments and competition had significant effects on growth of both clonal species in the apical sections, and their interaction was significant for A. philoxeroides but not for J. repens (Table 1)
With competition, clonal integration had no significant effect on the growth of A. philoxeroides but greatly enhanced that when its basal parts were in nutrientrich sections (Fig 2A, B, C, D, E)
Summary
Through which connected ramets of clonal plants can share water, carbohydrates,nutrients and other substances such as pollutants, diseases, etc. [1,2,3], may improve plants’ exploitation of ubiquitous heterogeneous resources, help plants invade new environments and facilitate plants’ spatial occupation of new habitats at a local scale [4]. Previous studies have shown that clonal integration may facilitate the colonization and growth of the ramets in heterogeneous habitats with stressful conditions [5,6], help genets to survive and to recover after severe environmental change [7,8] and allow for occupation of new space [9,10,11]. These positive effects of clonal integration may increase the performance of clonal plants over non-clonal plants or other clonal plants with little integration [12]. A better understanding of different clonal integration effects between alien invasive and native clonal plants when competing with each other is both scientific and practical interests
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