Three-genome mosses: complex double allopolyploid origins for triploid gametophytes in Sphagnum

Authors

  • ERIC F. KARLIN,

    1. School of Theoretical & Applied Science, Ramapo College, Mahwah, New Jersey 07430-1680, USA,
    Search for more papers by this author
  • S. B. BOLES,

    1. Duke University, Department of Biology, Durham, North Carolina 27708, USA,
    Search for more papers by this author
  • M. RICCA,

    1. Duke University, Department of Biology, Durham, North Carolina 27708, USA,
    2. Departamento de Botânica, Faculdade de Ciências da Universidade do Porto, Rua do, Campo Alegre 1181, 4150-191 Porto, Portugal and CIBIO, Centro de Investigação em, Biodiversidade e Recursos Genéticos, Universidade do Porto, Campus Agrário de, Vairão, 4485-661 Vairão, Portugal,
    Search for more papers by this author
  • E. M. TEMSCH,

    1. Department of Systematic and Evolutionary Botany, Faculty of Life Sciences, University of Vienna, Rennweg 14, A 1030 Vienna, Austria
    Search for more papers by this author
  • J. GREILHUBER,

    1. Department of Systematic and Evolutionary Botany, Faculty of Life Sciences, University of Vienna, Rennweg 14, A 1030 Vienna, Austria
    Search for more papers by this author
  • A. J. SHAW

    1. Duke University, Department of Biology, Durham, North Carolina 27708, USA,
    Search for more papers by this author

Eric Karlin, Fax: 201-684-7637; E-mail: ekarlin@ramapo.edu

Abstract

This paper documents the occurrence of allotriploidy (having three differentiated genomes) in gametophytes of two Southern Hemisphere Sphagnum species (S. australe, S. falcatulum). The pattern of microsatellite alleles indicates that both species are composed of a complex of allodiploid and allotriploid gametophytes, with the latter resulting from two allopolyploidization events. No haploid (n = x) gametophytes were found for either species. The ploidal levels suggested by the pattern of microsatellite alleles were confirmed by flow cytometry and Feulgen DNA image densitometry. For both S. australe and S. falcatulum, the respective allodiploid plants (or their ancestors) are one of the parent species of the allotriploid plants. This is the first report of triploidy in Sphagnum gametophytes occurring in nature and also the first report of the presence of three differentiated genomes in any bryophyte. It is also the first report of intersectional allopolyploidy in Sphagnum, with S. australe appearing to have parental species from Sphagnum sections Rigida and Sphagnum, and S. falcatulum having parental species from Sphagnum sections Cuspidata and Subsecunda. In both species, the allotriploid cytotypes were the most prevalent cytotype on the South Island of New Zealand. The pattern of microsatellite alleles shows the presence of two genetically distinct populations of allodiploid S. australe, possibly indicating multiple origins of polyploidy for that allodiploid cytotype. Morphological evidence is also highly indicative of recurrent polyploidy in the allotriploid cytotype of S. falcatulum. Allopolyploidy has clearly played a major evolutionary role in these two Southern Hemisphere taxa. This study, in conjunction with other recent research, indicates that allopolyploidy is a common, if not the predominant, form of polyploidy in Sphagnum.

Ancillary