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  • base
  • Although there has been a remarkable evolutionary and morphologic diversification in North American Cirsium , it has not been accompanied by very much divergence in the base sequences of genes commonly used to elucidate phylogenetic relationships. (efloras.org)
  • field
  • In other cases hybridization has been invoked without much evidence as an explanation for Cirsium variants encountered in herbaria or in the field. (efloras.org)