You Wen-Hua, Han Cui-Min, Fang Long-Xiang, Du Dao-Lin
Institute of Environment and Ecology, College of the Environment and Safety Engineering, Jiangsu University Zhenjiang, China.
Front Plant Sci. 2016 May 3;7:568. doi: 10.3389/fpls.2016.00568. eCollection 2016.
Many notorious invasive plants are clonal, spreading mainly by vegetative propagules. Propagule pressure (the number of propagules) may affect the establishment, growth, and thus invasion success of these clonal plants, and such effects may also depend on habitat conditions. To understand how propagule pressure, habitat conditions and clonal integration affect the establishment and growth of the invasive clonal plants, an 8-week greenhouse with an invasive clonal plant, Alternanthera philoxeroides was conducted. High (five fragments) or low (one fragment) propagule pressure was established either in bare soil (open habitat) or dense native vegetation of Jussiaea repens (vegetative habitat), with the stolon connections either severed from or connected to the relatively older ramets. High propagule pressure greatly increased the establishment and growth of A. philoxeroides, especially when it grew in vegetative habitats. Surprisingly, high propagule pressure significantly reduced the growth of individual plants of A. philoxeroides in open habitats, whereas it did not affect the individual growth in vegetative habitats. A shift in the intraspecific interaction on A. philoxeroides from competition in open habitats to facilitation in vegetative habitats may be the main reason. Moreover, clonal integration significantly improved the growth of A. philoxeroides only in open habitats, especially with low propagule pressure, whereas it had no effects on the growth and competitive ability of A. philoxeroides in vegetative habitats, suggesting that clonal integration may be of most important for A. philoxeroides to explore new open space and spread. These findings suggest that propagule pressure may be crucial for the invasion success of A. philoxeroides, and such an effect also depends on habitat conditions.
许多臭名昭著的入侵植物都是克隆植物，主要通过营养繁殖体传播。繁殖体压力（繁殖体数量）可能会影响这些克隆植物的定殖、生长以及入侵成功率，而且这种影响可能还取决于栖息地条件。为了了解繁殖体压力、栖息地条件和克隆整合如何影响入侵克隆植物的定殖和生长，我们利用入侵克隆植物空心莲子草进行了为期8周的温室实验。在裸土（开阔生境）或水龙的茂密原生植被（营养生境）中设置了高（五个片段）或低（一个片段）繁殖体压力，匍匐茎连接要么与相对较老的分株切断，要么与之相连。高繁殖体压力极大地增加了空心莲子草的定殖和生长，尤其是当它生长在营养生境中时。令人惊讶的是，高繁殖体压力显著降低了空心莲子草在开阔生境中个体植株的生长，而在营养生境中却不影响个体生长。空心莲子草种内相互作用从开阔生境中的竞争转变为营养生境中的促进作用可能是主要原因。此外，克隆整合仅在开阔生境中显著促进了空心莲子草的生长，尤其是在低繁殖体压力下，而在营养生境中对空心莲子草的生长和竞争能力没有影响，这表明克隆整合对于空心莲子草开拓新的开阔空间和扩散可能最为重要。这些发现表明，繁殖体压力可能对空心莲子草的入侵成功至关重要，而且这种影响也取决于栖息地条件。
