Erigeron x pilosiusculus Sennikov, sp., 2023

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

2. Erigeron x pilosiusculus Sennikov, sp. hybr. nov.

Fig. 5

Type.

Russia. Karelian Republic : Paanajärvi, Kauppila, torr mark nära gården [= in colle sicco], 29.07.1936, H. Lindberg [ Plantae Finlandiae Exsiccatae no. 1369] (holotype H 039503 pro parte [plant 1]; isotypes H 339935 pro parte, OULU 059259) .

Description.

Stems 25-50 cm tall, branched in the upper third, intensely to slightly purple-coloured, covered by sparse to numerous hairs 0.5-1 mm long mostly in the basal half. Cauline leaves 4-8 under the synflorescence, spaced, gradually decreasing towards the stem top, unevenly covered by sparse hairs 0.5-1 mm long on both sides. Synflorescence with long branches carrying solitary to 2-3 capitula, nearly corymbose at the top, branches subglabrous or with sparse hairs. Phyllaries 6-7.5 mm long, purple-coloured completely or near the apex, covered by sparse hairs in the basal part or up to the apex. Ray flowers dark-lilac to pale-pinkish. Pappus greyish-white.

Flowers in July, fruits in July to August. As evident from the plants collected in mixed populations, the flowering and fruiting of the hybrid occur earlier than in its native parent, Erigeron politus . When plants of E. politus start to blossom, the hybrid is already in the last flowers. Distribution in Murmansk Region. Kandalaksha Gulf, Turii Mys, Varzuga River (lower course), Ponoi River (lower course) (Fig. 4B ).

Global distribution.

Subarctic and Northern Boreal zones of Fennoscandia.

Etymology.

The species epithet, meaning 'slightly more hairy’ (pilosior, Lat.: more hairy; - usculus, Lat.: diminutive suffix), was selected to reflect a slighly greater hairiness of the hybrid in comparison to its more glabrous parent, E. politus .

Nomenclature note.

The type collection is taxonomically mixed. It contains typical plants of E. rigidus and the hybrid, which is less hairy and slightly less vigorous. This collection was distributed by Lindberg (1944) in his exsiccatae but its specimens were formed by chance: some appear to contain plants of E. rigidus only (H 039491), some belong only to the hybrid (OULU 059259), whereas the others may be mixed on the same sheet (H 339935).

Taxonomic note.

The morphology of this taxon is intermediate between E. rigidus and E. politus . Such plants typically have stems and leaves rather hairy, sometimes close to the pubescence of E. rigidus but never as dense and abundant as in the latter. On the other hand, its involucres highly resemble those of E. politus but are very sparsely covered by hairs. Because of this intermediacy, such plants were identified either as E. politus or as E. rigidus , likely depending on which part of the plant was more closely observed. We cannot refer these intermediate plants to any of the species, and therefore assume their hybrid origin, which requires a separate taxonomic placement as proposed here.

The distribution of the alleged hybrids lies completely within the area of intense anthropogenic influence, whereas only typical plants of E. politus were observed in the areas of its presumably native distribution (higher mountains in the centre of the Kola Peninsula and the Kutsa River basin). We consider this distribution pattern as a strong evidence for the anthropogenic origin of the presumed hybrid, which was formed within the area to which both native and alien taxa of the E. acris group were transported by humans.

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 5. Holotype of Erigeron x pilosiusculus Sennikov (H 039503, plant 1). Courtesy of the Finnish Museum of Natural History, University of Helsinki.