Panarctic Flora

3420 Calamagrostis Adans.

• Adans., Fam. Pl. 2: 31, 530 (1763).
• Excluded: Calamagrostis chordorrhiza (see C. holmii below), C. kolymaensis (see the C. neglecta aggregate below).

Notes: Nearly every aspect of Calamagrostis has been discussed among the PAF collaborators, due to the complex variation pattern in this genus. A main reason is the genetics and the reproductive system. Nygren made an early, thorough investigation of cytology and its influence on reproduction in Calamagrostis, mainly on European species but also including North American ones (Nygren 1946, 1948a, 1948b, 1949c, 1954a, 1954b, 1958, 1962). Tateoka (1974, 1976) studied the variation in Japan, Greene (1980, 1984) in North America.

The northern plants are tetraploids and/or higher polyploids. The majority of tetraploids are sexual, the higher polyploids agamospermous. The higher polyploids may be taxonomic autoploids, alloploids, or a combination, and each of them may well be results of more than one hybridization event. Sexuals are mostly easily recognized by dehiscent anthers and viable pollen, whereas agamosperms normally are pollen-sterile with shrunken anthers that persist in the spikelet. Populations with partial anther and pollen development occur but in low frequencies (less than 2 % of inspected specimens from northern Europe and North America).

As in many other genera, there are competing proposals by Tzvelev (PAF proposal and elsewhere) mainly based on Eurasian variation but encompassing also the North American plants, and by Soreng and Greene in Soreng et al. (2003) and Marr et al. (2007) treating the American plants. Our account tries to balance these proposals but differs from both in one aspect. We accept sexuals and assumedly allopolyploid agamospermous offsprings as different species, where supported by morphological differences.

Tzvelev (1976) divided the northern species on three sections: sect. Deyeuxia (Clarion ex P. Beauv.) Dumort. with the species 01-08 below, sect. Calamagrostis with the species 09-12, and sect. Pseudophragmites Tzvelev (later as sect. Epigeios W.D.J. Koch due to priority) with species 13. We see four groups as two parts of sect. Deyeuxia have independent variation patterns: the C. purpurascens aggregate (species 01-03) and the group of C. deschampsioides, C. lapponica, C. neglecta, and relatives (species 04-08).