title: Origins and widespread distribution of co-existing Polyploids in Arnica cordifolia (Asteraceae).
abstract: OBJECTIVE
  Polyploidy is a central force structuring genetic diversity in angiosperms, but its ecological significance and modes of origin are not fully understood. This work investigated the patterns of coexistence and molecular relatedness of polyploids in the perennial herb, Arnica cordifolia.
  
  
  METHODS
  The local- and broad-scale distributions of cytotypes were analysed using flow cytometry. Samples were collected from both roadside and understorey habitats to test the hypothesis of niche separation between triploids and tetraploids. The nuclear rDNA internal transcribed spacer (ITS) and plastid rpl16 spacer, trnL intron plus trnL-trnF spacer and trnK 3' intron regions were sequenced.
  
  
  RESULTS
  Broad-scale sampling established that both triploids and tetraploids were common throughout the range of the species, pentaploids were rare, and diploids were not found. Local-scale sampling revealed coexistence of both triploids and tetraploids within the majority of sites. Triploids and tetraploids were equally represented in the understorey and roadside habitat. Triploids were more variable than tetraploids, but both cytotypes shared polymorphisms in ITS.
  
  
  CONCLUSIONS
  Coexistence of cytotypes appears to be the norm in A. cordifolia, but habitat differentiation (roadside vs. understorey) is not supported as a coexistence mechanism. Molecular analyses supported multiple events creating triploids but revealed a lack of variation in the tetraploids. Additionally, sequence polymorphisms in ITS suggested a hybridization event prior to polyploidization.
authors.affiliation: University of California Santa Cruz, EE Biology, EMS A316, 1156 High St, Santa Cruz, CA 95064, USA. rhkao@lamar.colostate.edu
authors.forename: Rebecca Hufft
authors.initials: RH
authors.lastname: Kao
mesh_terms: D018650:Arnica / Q000145:classification / Q000235:genetics*; D003120:Colorado; D018742:DNA, Chloroplast / Q000737:chemistry; D021901:DNA, Intergenic / Q000737:chemistry; D017753:Ecosystem; D006239:Haplotypes; D006824:Hybridization, Genetic; D019601:Pacific States; D011110:Polymorphism, Genetic; D011123:Polyploidy; D017422:Sequence Analysis, DNA
chemical_list: D018742:DNA, Chloroplast; D021901:DNA, Intergenic