Erigeron x intercalaris 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

4. Erigeron x intercalaris Sennikov, sp. hybr. nov.

Fig. 7

Type.

Russia. Karelian Republic : Louhi District, “Paanajärvi, Rajala, vägkant vid Mäntyjoki” [= northern side of Paanajärvi Lake, roadside between formerly populated places], 22.07.1936, H. Lindberg (holotype H 039504) .

Description.

Stems 30-50 cm tall, branched in the upper third or half, intensely to slightly purple-coloured, evenly covered by numerous hairs 1-2 mm long. Cauline leaves 4-8 under the synflorescence, spaced, gradually decreasing towards the stem top, completely covered by numerous hairs 0.5-1(1.5) mm long on both sides or subglabrous at the base below. Synflorescence with long branches carrying solitary to 2-3 capitula, nearly corymbose at the top, with numerous hairs 0.8-1 mm long. Phyllaries 6-7.5 mm long, purple-coloured completely or in the apical part, abundantly covered by hairs 1-2 mm long. Ray flowers intensely lilac. Pappus greyish-white.

Flowers in July to August, fruits in August.

Distribution in Murmansk Region.

Tetrino Village, Apatity Town (Fig. 4D ).

Global distribution.

Expected in the Boreal zone of Fennoscandia and Eastern Europe.

Etymology.

The species epithet (intercalaris, Lat.: intercalary) reflects the intermediate morphology of the hybrid between its presumed parents. Nomenclatural note. The type locality has been extensively sampled for Erigeron plants, which were distributed by Lindberg (1944) in his exsiccatae. The material from the Mäntyjoki River distributed as Plantae Finlandiae Exsiccatae 1370 is taxonomically heterogeneous: a few plants of E. acris s.str. (H 339936 pro parte) were mixed with abundant collections of its hybrid with E. rigidus (H 339936 pro parte, H 039487, OULU 059260). The latter specimens are paratypes of our E. x intercalaris . The hybrid plants look very slender and depressed, much less vigorous than the specimens of E. acris s.str. collected in the same locality, thus probably indicating outbreeding depression ( Bleeker et al. 2007).

Taxonomic note.

The hybrid differs from E. acris in a regular purple colouration of its stems and phyllaries, and in a shorter and sparser pubescence on its leaves and stems. It differs from E. rigidus in a denser and longer hairiness of its stems, leaves and phyllaries, and in a lesser purple colouration of its stems and phyllaries.

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 7. Holotype of Erigeron x intercalaris Sennikov (H 039504). Courtesy of the Finnish Museum of Natural History, University of Helsinki.