title: Clonal integration increases relative competitive ability in an invasive aquatic plant.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: School of Nature Conservation, Beijing Forest University, Beijing 100083, China.|Biology Department, University of Massachusetts, Amherst, Massachusetts 01003, USA.
authors.forename: Pu
authors.initials: P
authors.lastname: Wang
authors.affiliation: Biology Department, University of Massachusetts, Amherst, Massachusetts 01003, USA.
authors.forename: Peter
authors.initials: P
authors.lastname: Alpert
authors.affiliation: School of Nature Conservation, Beijing Forest University, Beijing 100083, China feihaiyu@bjfu.edu.cn.
authors.forename: Fei-Hai
authors.initials: FH
authors.lastname: Yu
mesh_terms: D059001:Aquatic Organisms; D029064:Araceae / Q000502:physiology*; D002999:Clone Cells; D017753:Ecosystem; D031806:Eichhornia / Q000502:physiology*; D058865:Introduced Species; D012098:Reproduction
keywords: Eichhornia crassipes; Pistia stratiotes; aquatic; clonal plant; floating; fragmentation; interspecific competition; invasive species; physiological integration