Erigeron rigidus Fr., Novit. Fl. Suec. Mant. III: 107 (1843)

Sennikov, Alexander N. & Kozhin, Mikhail N., 2023, Taxonomic revision of the Erigeron acris group (Asteraceae) in Murmansk Region, Russia, reveals a complex pattern of native and alien taxa, PhytoKeys 235, pp. 83-128 : 83

3. Erigeron rigidus Fr., Novit. Fl. Suec. Mant. III: 107 (1843)

Fig. 6

Erigeron acris rigidus - Erigeron acris var. rigidus (Fr.) A.Blytt, Norges Fl. 2: 562 (1874) - Erigeron politus subsp. rigidus (Fr.) Jørg. in Forh. Vidensk.-Selsk. Kristiania 1894(8): 27 (1894).

Erigeron acris ruber = Erigeron acris var. ruber Hartm., Handb. Skand. Fl., ed. 1: 315 (1820). Type. Sweden. Lule lappmark, S.N. Casström (holotype S, not traced).

Type.

Norway. Filefjell: Nystuen, M. Blytt (lectotype UPS, designated here) .

Description.

Stems 25-50 cm tall, branched in the upper third, intensely to slightly purple-coloured, evenly covered by numerous hairs 0.5-1 mm long. Cauline leaves 4-8(12) under the synflorescence, spaced, gradually decreasing towards the stem top, completely covered by numerous hairs 0.5-1 mm long on both sides but subglabrous at the base below. Synflorescence with long branches carrying solitary to 2-3 capitula, nearly corymbose at the top, with numerous hairs 0.4-0.7 mm long. Phyllaries 6-7.5 mm long, purple-coloured completely or in the apical part, rather densely covered by hairs up to 0.5-0.8 mm long. Ray flowers intensely lilac. Pappus greyish-white.

Flowers in July to August, fruits in August.

Distribution in Murmansk Region.

Coastal area of the White Sea, road from Alakurtti to Salla and Vuorijarvi Village, isolated at Kirovsk Town, Zasheyek Village and Kola Town (Fig. 4C ).

Global distribution.

Boreal zone of Fennoscandia and Eastern Europe, southern limit unknown.

Nomenclature note.

Fries (1843a) mentioned two areas from which his new species was described, Filefjeld in Norway and Norrland in Sweden. The Norwegian report was based on a single specimen collected by M. Blytt in Nystuen and cited in the protologue, which is a syntype. The basis for the Swedish part of the distribution area was not specified in the protologue but Fries indicated by an exclamation mark that he had seen some (otherwise uncited) material. The specimen collected by Blytt has been traced at UPS (Hjertson, pers. comm.) and is designated as lectotype here. Hartman (1820) described Erigeron acris var. ruber Hartm. from Swedish Lapland, which was briefly characterised by “dark-red” ligulate flowers. This character indicates that the plant was intensely purple-coloured; together with its occurrence in Lapland, this character unambiguously points at E. rigidus . Quite exceptionally in those times, the protologue of E. acris var. ruber Hartm. ( Hartman 1820) included citation of a single specimen collected by Samuel Niclas Casström, which is apparently the holotype. The collections of Casström were bequeathed after his death to the Swedish Museum of Natural History ( Lindman 1916), where the holotype should be currently kept (not traced).

Taxonomic note.

This species is most similar to Erigeron acris s.str., from which it differs in typically red stems and phyllaries, and in sparser and shorter pubescence on stems, leaves and phyllaries. Its distribution area remains unknown due to the ongoing confusion with E. acris s.str.; so far, we feel certain to state that E. rigidus is common in southern Finland and Karelia, together with E. acris s.str., but goes farther northwards than the latter species. In Central and Southern Europe there is another similar taxon, E. muralis Lapeyr. (= E. serotinus Weihe), which apparently differs in its habit and much denser foliage ((10)17-27(40) stem leaves in E. muralis vs. 4-8(12) stem leaves in E. rigidus ) ( Šída 2004). Besides, E. rigidus flowers together with E. acris , whereas the flowering of E. muralis occurs much later ( Šída 2001)

Figures

Figure 4. Distribution of the Erigeron acris group in Murmansk Region, Russia A E. politus F. B E. x pilosiusculus Sennikov C E. rigidus Fr. D E. x intercalaris Sennikov. Origin and residence status: green - native; yellow - pre-industrial alien; red - industrial alien. Maps were created using ArcGIS software by Esri. ArcGIS is the intellectual property of Esri and is used herein under license. Copyright Esri. All rights reserved.

Figure 6. Lectotype of Erigeron rigidus Fr. (UPS). Courtesy of the Museum of Evolution, Uppsala University.