Cytotaxonomy of the genus Smilacina (liliaceae)

Summary

• 1. The chromosome number of three North American Smilacina species was determined as 2n=72 for S. racemosa, and 2n=36 for S. stellata and S. trifolia. Octoploidy (2n=72) in S. racemosa had previously been unreported for both this species and the genus.

• 2. The karyotype of these three species was analyzed, as follows: S. racemosa: K (2n) = 72 = 14 V + 24 J + 34 v (or 4 j + 30 v); S. stellata: K (2n) = 36 = 6 V + 14 J + 10 v; S. trifolia: K (2n) = 36 = 4 V + 16 J + 10 v. Karyotypic affinity between S. stellata and S. trifolia is great, substantiating a phylogerietic relationship already indicated by morphological similarity.

• 3. The taxonomic problems of the morphologically as well as karyologically heterogeneous S. racemosa complex is briefly discussed in relation to cytology. All Wisconsin collections proved to be octoploid with 2n=72. The exact taxonomic position or geographic origin of the plant called “racemosa” by Therman (1956), in which 2n=36 chromosomes were counted, is unknown. It was not possible to establish as yet whether or not there is any definite correlation between karyology and morphology in this group, in effect between tetraploidy vs. octoploidy on the one hand and the poorly defined morphological varieties cylindrata in the south vs. racemosa in the north. Whether the octoploid arose from autoploidy out of the southeastern populations, or from amphiploidy as a result of the latter crossing with a western postglacial immigrant are two possibilities that are discussed but not verified. The S. racemosa complex promises to be a rewarding object of cyto-geographic analysis.