Karyotypic Relationships among Elmera, Heuchera, and Tellima (Saxifragaceae)

In the hope of clarifying relationships among Elmera, Heuchera, and Tellima, karyo- types of E. racemosa, nine species of Heuchera, and T. grandiflora were compared. This and a previous study have demonstrated karyotypic constancy in Heuchera; thirteen species of Heuchera, repre- senting all five sections have essentially identical karyotypes. Heuchera and the monotypic genera Elmera and Tellima have distinctive karyotypes, and that of Elmera appears to be most similar to that of Heuchera. Karyological data agree with palynological and flavonoid data, which also indicate that Elmera is distinct from Heuchera and Tellima and should be maintained as a separate genus. Hy-banding revealed prominent centromeric and telomeric heterochromatin, which confirmed the karyotypes proposed based on gross chromosomal morphology and permitted differentiation of several of the shorter chromosome pairs that morphologically are very similar. The relative ease with which chromosomes of Heuchera, Elmera, and Tellima respond to the Hy-banding procedure and the large amounts of heterochromatin present is similar to earlier observations for Mitella, Tiarella, and Tolmiea. This investigation further illustrates the conservative nature of chromosomal evolution in taxa of Saxifrageae characterized by x = 7.