The biosystematics of Trillium rugelii from Rutherford County, North Carolina

A karyotypic and statistical study was made of samples from three populations of Trillium rugelii Rendle from Rutherford County, North Carolina. The data collected were compared with the karyotypes and statistics for Trillium flexipes Raf. (T. gleasoni Fern.) from western North Carolina and Tennessee, and for five members of the T. erectum L. complex. Trillium rugelii grows sympatrically with T. grandiftorum (Michx.) Salisb. and T. cuneatum Raf., two species which are morphologically dissimilar to it; but it is geographically isolated from T. flexipes and members of the T. erectum complex, the taxa which are morphologically most similar to it. The modal karyotypic comparison and the scatter diagrams correlate to show that this taxon is closely related to T. erectum var. album (Michx.) Pursh, T. simile Gleason, and probably to T. flexipes. There is evidence of distinct karyotypic variability among individual plants in T. rugelii. Although no chromosome types are peculiar to this taxon, there are no plant karyotypes (diploid sets) identical with those for T. rugelii among the seven taxa compared with it. Habit characters make this plant easily identified in the field. Taxonomic recognition for T. rugelii is justified. Further studies are required to determine to which rank it should be assigned.