title: Competition between cytotypes changes across a longitudinal gradient in Centaurea stoebe (Asteraceae).
abstract: OBJECTIVE
  Polyploidy resulting from whole genome duplication has contributed to the adaptive evolution of many plant species. However, the conditions necessary for successful polyploid evolution and subsequent establishment and persistence in sympatry with diploid progenitors are often quite limited. One condition thought to be necessary for establishment is a substantial competitive superiority of the polyploid.
  
  
  METHODS
  We conducted a pairwise competition experiment using diploid and tetraploid cytotypes of Centaurea stoebe L. to determine whether (1) tetraploids have greater competitive ability than diploids, (2) cytotypes from mixed-cytotype populations have more balanced competitive abilities than single-cytotype populations, and (3) competitive abilities change along a longitudinal gradient.
  
  
  RESULTS
  Across sampling localities, tetraploids did not produce greater aboveground biomass than diploids but suffered from greater intracytotypic competition. Tetraploids allocated greater biomass belowground than diploids, regardless of competition treatment, and had greater performance for traits associated with long-term persistence (bolted more frequently and produced more accessory rosettes). Competitive ability of tetraploids did not differ between single- and mixed-cytotype populations but varied along a longitudinal gradient. Tetraploids were stronger intercytotypic competitors in Western Europe (Switzerland and Germany) than in Eastern Europe (Hungary and Slovakia), which indicates that cytotype coexistence may be more likely in Eastern Europe, the proposed origin of tetraploids, than in Western Europe.
  
  
  CONCLUSIONS
  Our study addresses the importance of examining competitive interactions between cytotypes across their distributional range, as competitive interactions were not consistent across sampling localities.
authors.affiliation: University of Fribourg, Ecology and Evolution Department, Fribourg, Switzerland. robin.collins@unifr.ch
authors.forename: Alexandra R
authors.initials: AR
authors.lastname: Collins
authors.forename: Ruhollah
authors.initials: R
authors.lastname: Naderi
authors.forename: Heinz
authors.initials: H
authors.lastname: Mueller-Schaerer
mesh_terms: D000704:Analysis of Variance; D018533:Biomass; D031179:Centaurea / Q000235:genetics*; D060146:Ecotype; D005060:Europe; D005843:Geography; D016015:Logistic Models; D018517:Plant Roots / Q000033:anatomy & histology; D018520:Plant Shoots / Q000033:anatomy & histology; D011123:Polyploidy; D011157:Population Dynamics; D012639:Seeds / Q000254:growth & development; D013997:Time Factors