NUMERICAL TAXONOMY OF LIMNANTHACEAE

A numerical taxonomic study of the angiosperm family Limnanthaceae is presented. The 21 OTUs include all taxa recognized in a recent monograph of Limnanthes (Mason, 1952), plus Floerkea proserpinacoides, two undescribed Limnanthes species, and two artificial interspecific F₁ Limnanthes hybrids. One species (L. montana) was treated as two OTUs: measurements for one OTU were taken from field collections and for the other, from garden-grown plants. A maximum of 35 characters was used in the numerical analyses. Raw data for each character were given equal weighting by condensation. Coefficients of resemblance were established using the mean character difference (MCD) method. Tryon's clustering technique (called key communality cluster analysis) was used. Three numerical analyses of Limnanthaceae were made: one with all 35 characters (T analysis), one with 18 floral characters (F analysis), and one with 17 pre- or post-anthesis or vegetative characters (V analysis). Relative positions of OTUs in the T and F analyses are substantially different from those in a conventional taxonomic treatment of the family. The V analysis shows many differences from the T and F analyses. In all analyses the two OTUs representing L. montana were closer to other OTUs than to each other. The two hybrid OTUs showed greater resemblance to one parent than to the other and in two analyses one hybrid was not intermediate between the parents. Similarities between the T and F analyses are explained on the basis of the predominance of floral characters in both. The differences between these two analyses on the one hand and the V analysis and phylogenetic arrangement of the family on the other are attributed to parallelisms in the evolution of floral characters associated with iucreasing autogamy in each of the two phyletic lines in the family. Analyses emphasizing floral characters will place evolutionarily remotely related outcrossing OTUs together and unrelated, autogamous OTUs together. Using characters that are mostly unassociated with the breeding system the positions of OTUs in a numerical analysis are similar to their positions in a phylogenetic arrangement. The V analysis agrees best with suggestions concerning phylogenetic affinities among the taxa in the family, and provides a useful context for the generation of further evolutionary hypotheses.