The taxonomic circumscription of Aconitum subgenus Aconitum (Ranunculaceae) in Europe

In this article, we present a revised taxonomic circumscription of Aconitum subg. Aconitum (Ranunculaceae) in Europe. In total, the subgenus contains some 250 species with the major center of diversity in Eastern Asia. Altogether 94 taxa (species and infraspecific taxa, including hybrids) occur in Europe. Among them, 22 are native species, and 28 are nothospecies (including hybrid formulae). The research is based on former (since Linnaeus) and recent species diagnoses integrating herbarium and field studies carried out in the Alps, Carpathians, Balkans, Spanish Sierra Nevada, Sudetes, and Corsica. The subgenus includes three sections in Europe: the diploid sect. Cammarum, the tetraploid sect. Aconitum, and the monospecific, allopolyploid sect. Angustifolium. Additionally, a triploid, hybridogenous nothosection Acomarum (sect. Aconitum × sect. Cammarum) is presented. For each species, type citation, a concise morphological description, including infraspecific variation and hybridization, geographical distribution, and iconography sources are given. Also, a key to the determination of all taxa is presented. The proposed system scrutinizes former and recent species concepts and gives a base for further studies on the genus’ phylogeny and biotechnology.


INTRODUCTION
The genus Aconitum L. (monkshood) comprises ca. 300-400 species distributed in temperate regions of the northern hemisphere, with a center of diversity in the eastern Himalaya, southwestern China, and Japan (Kadota 1987;Li and Kadota 2001;Luo et al. 2005). From a total number of ca. 250 species belonging to the subgenus Aconitum, 22 species may be found in Europe, with eight species occurring exclusively in the Carpathian and Balkans Mts (Boroń et al. 2020). The subgenus includes both the "temperate" forest (diploid) and "cold" high-mountain (tetraploid) species, which are differentiated both morphologically (Starmühler 1998;Mitka 2003;Novikoff and Mitka 2011) and cytogenetically Mitka 2009, 2011).

MATERIAL AND METHODS
We have evaluated all recognized taxa from the Aconitum subg. Aconitum distributed in Europe based on our experience of many years of field investigations, morphological and biogeographical studies, as well as analysis of herbarium material. For each taxon, we provided comprehensive data on its distribution and morphological characteristics. We reviewed all available sources for taxon synonymy and type citations. Basing on morphological data, a binary key for the identification of the representatives of the subgenus Aconitum has been developed. 10 Aconitum sect. Angustifolium Rottensteiner consists of one species (Seitz 1969).

Diagnosis
A. ×mariae differs from A. firmum by glandular pilose pedicels and differs from A. maninense by glabrous tepals.

Description
Inflorescence axis glabrous, pedicels glandular pubescent and pilose, often only above the bracteoles, bracteoles linear, lanceolate, spathulate or even divided, situated in the upper half of the pedicel, tepals outside glabrous, filaments of the stamens glabrous or sparsely pilose, carpels glabrous or sparsely pilose on the backside.

Diagnosis
Spurs of nectaries are elongated and backward bent.

Description
Monotypical series with only one species, separated from the other series of subsection Aconitum by the unique character of the elongated and backward bent spur of the nectaries. Diagnostic characters: stem and leaves glabrous or glabrescent; inf lorescence ramified, curved eglandular pubescent; hood hemispheric-falciform; nectaries hardly curved, spur of the nectaries elongated and bent backward; filaments not dentate, pilose; carpels 3-5, glabrous.

Diagnosis
Carpels totally or partially sterile.