The allotetraploid Saxifraga nathorsti and its probable progenitors S. aizoides and S. oppositifolia

Abstract

Saxifraga nathorsti is an endemic Greenland species geographically restricted to Northeast Greenland. Morphologically it is intermediate between Saxifraga oppositifolia with purplish petals and S. aizoides with yellow petals. A hybrid between these two species is difficult to obtain and is not known from Greenland or anywhere else.

New material from Northeast Greenland has been cultivated and studied cytologically. One strain of typical S. nathorsti corresponded to the material studied previously. It also had 52 chromosomes and showed a high degree of pairing during meiosis. It was fertile, but exhibited several meiotic irregularities. Another strain seemed morphologically more closely related to S. oppositifolia. It was sterile and had the triploid number 2n = 39. It was assumed to have two genomes from S. oppositifolia and one from S. aizoides. It appears most probable that triploids of this kind after fertilization with pollen from S. aizoides can give rise to S. nathorsti.

Anatomical studies of the structure of epithem hydathodes in S. nathorsti and its two possible ancestors, S. oppositifolia and S. aizoides, show that S. nathorsti in several important hydathode characters occupies an intermediate position between S. oppositifolia and S. aizoides. Thus, all available facts support the theory of the origin and stabilization of S. nathorsti as an allotetraploid species.