Introgressive hybridization between anciently diverged lineages of Silene (Caryophyllaceae)

PLoS One. 2013 Jul 8;8(7):e67729. doi: 10.1371/journal.pone.0067729. Print 2013.


Hybridization has played a major role during the evolution of angiosperms, mediating both gene flow between already distinct species and the formation of new species. Newly formed hybrids between distantly related taxa are often sterile. For this reason, interspecific crosses resulting in fertile hybrids have rarely been described to take place after more than a few million years after divergence. We describe here the traces of a reproductively successful hybrid between two ancestral species of Silene, diverged for about six million years prior to hybridization. No extant hybrids between the two parental lineages are currently known, but introgression of the RNA polymerase gene NRPA2 provides clear evidence of a temporary and fertile hybrid. Parsimony reconciliation between gene trees and the species tree, as well as consideration of clade ages, help exclude gene paralogy and lineage sorting as alternative hypotheses. This may represent one of the most extreme cases of divergence between species prior to introgressive hybridization discovered yet, notably at a homoploid level. Although species boundaries are generally believed to be stable after millions of years of divergence, we believe that this finding may indicate that gene flow between distantly related species is merely largely undetected at present.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biological Evolution*
  • DNA Primers / metabolism
  • DNA-Directed RNA Polymerases / genetics
  • Gene Duplication
  • Genes, Plant / genetics
  • Genetic Variation*
  • Hybridization, Genetic*
  • Phylogeny
  • Plant Proteins / genetics
  • Silene / enzymology
  • Silene / genetics*


  • DNA Primers
  • Plant Proteins
  • DNA-Directed RNA Polymerases

Grant support

This work was supported by grants from Helge Ax:son Johnssons fund ( and the Lundgrenska fund ( to AP, and from the Swedish Research Council ( to BO (2006–3766 and 2009–5202). BEP is supported by grants from the Swedish Research Council (2009–5206), the Royal Swedish Academy of Sciences (, Lars Hiertas Minne fund (, The Royal Physiographic Society in Lund (, Helge Ax:son Johnsons fund and the Lundgrenska fund. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.