title: Escape from competition: neighbors reduce Centaurea stoebe performance at home but not away.
abstract: The greater abundance of some exotic plants in their nonnative ranges might be explained in part by biogeographic differences in the strength of competition, but these competitive effects have not been experimentally examined in the field. We compared the effects of neighbors on the growth and reproduction of spotted knapweed (Centaurea stoebe) in Europe, where it is native, and in Montana, where it is invasive. There were strong negative competitive effects of neighboring vegetation on C. stoebe growth and reproduction in Europe. In contrast, identical experiments in Montana resulted in insignificant impacts on C. stoebe. Although the mechanisms that produce this dramatic biogeographic difference in competitive outcome remain unknown, our results indicate that differences in net competitive interactions between ranges may contribute to the striking dominance of C. stoebe in parts of North America.
authors.affiliation: Division of Biological Sciences, University of Montana, Missoula, Montana 59812, USA. ray.callaway@mso.umt.edu
authors.forename: Ragan M
authors.initials: RM
authors.lastname: Callaway
authors.forename: Lauren P
authors.initials: LP
authors.lastname: Waller
authors.forename: Alecu
authors.initials: A
authors.lastname: Diaconu
authors.forename: Robert
authors.initials: R
authors.lastname: Pal
authors.forename: Alexandra R
authors.initials: AR
authors.lastname: Collins
authors.forename: Heinz
authors.initials: H
authors.lastname: Mueller-Schaerer
authors.forename: John L
authors.initials: JL
authors.lastname: Maron
mesh_terms: D031179:Centaurea / Q000254:growth & development*; D006814:Hungary; D058865:Introduced Species; D009009:Montana; D012383:Romania