Wang Pu, Alpert Peter, Yu Fei-Hai
School of Nature Conservation, Beijing Forest University, Beijing 100083, China.
Biology Department, University of Massachusetts, Amherst, Massachusetts 01003, USA.
Am J Bot. 2016 Dec;103(12):2079-2086. doi: 10.3732/ajb.1600160. Epub 2016 Dec 13.
Physiological integration between connected ramets is well known to increase performance of clonal plant species. However, no direct evidence appears to exist that integration can increase the ability of clonal species to compete with other species within mixed communities. We tested this hypothesis using two floating, invasive, aquatic species in which fragmentation-and thus extent of integration-is likely to vary between habitats and times.
Individual ramets of Pistia stratiotes and Eichhornia crassipes were grown in monoculture or in mixture, and new stolons bearing new offspring were severed or left intact. After 6 wk, the numbers of offspring and second-generation (2°) offspring produced by each original ramet, or parent, were counted; and the final dry mass of each parent, its stolons, its offspring, and its 2° offspring were measured.
Fragmentation decreased the relative competitive ability of Pistia, but not that of Eichhornia. This was mainly because Pistia accumulated ∼30% less dry mass of offspring when fragmented and grown with Eichhornia than in other treatments. Offspring of Pistia were smaller than those of Eichhornia in all treatments.
Our results show that clonal integration can increase competitive ability in some clonal species. In this case, integration appeared to enable the small offspring of Pistia to compete more effectively with the large offspring of Eichhornia. Lower rates of fragmentation may select for production of more numerous, smaller vegetative offspring in clonal species.
众所周知，相连分株之间的生理整合能提高克隆植物物种的性能。然而，似乎没有直接证据表明整合能增强克隆物种在混合群落中与其他物种竞争的能力。我们使用两种漂浮的入侵水生植物对这一假设进行了测试，在这两种植物中，分株破碎程度以及整合程度可能因栖息地和时间而异。
将大薸和凤眼莲的单个分株单独种植或混合种植，并将带有新子代的新匍匐茎切断或保持完整。6周后，统计每个原始分株（即亲本）产生的子代和第二代子代数量；并测量每个亲本、其匍匐茎、其后代及其第二代子代的最终干质量。
分株破碎降低了大薸的相对竞争能力，但未降低凤眼莲的相对竞争能力。这主要是因为大薸在与凤眼莲一起生长且分株破碎时积累的子代干质量比在其他处理中少约30%。在所有处理中，大薸的子代都比凤眼莲的子代小。
我们的结果表明，克隆整合可以提高某些克隆物种的竞争能力。在这种情况下，整合似乎使大薸的小子代能够更有效地与凤眼莲的大子代竞争。较低的分株破碎率可能会促使克隆物种产生更多数量、更小的营养子代。
