• crossing experiments;
  • isozymes;
  • offspring analysis;
  • pseudogamy;
  • species delimitation.

The degree of sexual seed set and the ability to cross were investigated in three taxa of Potentilla section Niveae (P. chamissonis, P. insularis and P. nivea) from the Svalbard Archipelago. Emasculated and bagged flowers had little or no seed set, while 71% of the emasculated, bagged and pollinated flowers had some. The taxa are interpreted as pseudogamous apomicts. Parental plants and offspring were subjected to isozyme analysis. Most of the offspring were clones of the mother plant, but 1.7% had bands from the pollen donor. The sexual offspring were all produced by mother plants of P. insularis, which is interpreted as a facultative apomict. Surprisingly, crosses between different taxa gave higher seed to ovule ratios and numbers of sexually produced offspring than crosses within taxa. Some of the sexually produced hybrid offspring had the same kind of hairs on the petioles as their mother taxon, showing that hybrids may not be intermediate in hair characters, which are considered important in the delimitation of these taxa. The results of the present study indicate very close relationships among the investigated plants. © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society, 2003, 142, 373−381.