Morphometrics and taxonomy of Erigeron acris sensu lato (Asteraceae) in Fennoscandia

Morphometric multivariate analysis has been performed based on 23 characters observed on 113 herbarium specimens from throughout Fennoscandia. This demonstrates that four taxa can be recognised within Erigeron acris L. sensu lato, viz. E. acris L. subsp. acris, E. acris subsp. decoloratus (H. Lindb.) Hiitonen, E. acris subsp. droebachiensis (O. F. Müll.) Arcang. and E. acris subsp. politus (Fr.) H. Lindb. In contrast, the previously accepted E. (acris subsp.) brachycephalus H. Lindb. is shown to be indistinguishable from E. acris subsp. droebachiensis and is accordingly treated as a synonym. The subspecies are distinguishable mainly based on indumentum characteristics, and size and pigmentaton of phyllaries and floral parts, but 21 of the 23 characters were significantly different among taxa. The largest number (ten) of significantly different characters was found between subspecies acris, droebachiensis and politus, whereas only five characters differed significantly between decoloratus and acris. The contrasting character ranges and distinctness of these taxa is presented and discussed, and a key to the subspecies is provided. In addition, their distributions in Sweden are mapped based on herbarium specimens, showing that subsp. acris is common almost throughout the country, subsp. droebachiensis is relatively rare and restricted to the central parts, and subsp. politus is confined to the northern half.