The genus Trollius L. (Ranunculaceae) in the flora of the Altai Mountain Country

Information on new characters, that were not previously used for the Trollius species identification is presented: consistence and degree of dissection of blade, type of margin, shape of teeth, number of petal veins, shape of nectarostigma, and morphological characters of fruits – type of the pericarp surface. The quantitative and qualitative morphological characters of the species are indicated: number of sepals and petals, distance from the petal base to the nectarostigma, length of the follicle and persistent style, as well as its shape and location. An identification key is proposed, which has been developed taking into account the suggested characters. A sinopsis of the genus Trollius (Ranunculaceae) of the Altai Mountain Country, including 3 species belonging to 2 sections is given. The synopsis includes nomenclature quotations, information on type specimens, distribution in the region, and general distribution for each species.

The genus Trollius L. includes с. 35 species (excluding Hegemone Bunge ex Ledeb.) distributed in the extratropical regions of the Northern Hemisphere. Hegemone is treated as a distinct genus (Schipczinsky, 1937). The common name of some species is "globeflower" (globe flower) or "Trollblume" (Stearn, 1992). The genus is characterized by conspicuous orange-or yellow-colored flowers, similarly colored petals, subscapose habit, and ternate or deeply 3-lobed leaves (Kadota, 1987). Trollius is characterized by an unusual floral structure with petals divided into the blade, pit (nectarostigma) and claw (Wang et al., 2010). The length ratio of nectaries to stamens was considered to be one of the most important morphological characters for species delimitation (Schipczinsky, 1937;Siplivinsky, 1972).
A. Doroszewska (1974) divided the genus into seven sections. Sections are mostly natural, but the gaps among them seem to be too small to assume them as distinct ones (Tamura, 1995). In Russia, about 19-20 species are recognized (Luferov et al., 2018). The greatest species diversity is observed in Siberia (12 species: our data). Eleven species of Trollius were previously indicated for that region (Friesen, 2003). Many taxa described recently from Russia (Malyshev, 1965, Siplivinsky, 1972, 1973Stepanov, 1994Stepanov, , 2018 require more detailed investigation and evidence of species independence (Luferov et al., 2018).
The Altai Mountains, sometimes referred to the Altai Mountain Country (AMC), are located in the borderland between Russia, Kazakhstan, China, and Mongolia (Kamelin, 2005). The AMC is situated in the western part of the Altai-Sayan ecoregion and stretches from approximately of N 45° to 54°, and E 80° to 100° as outlined by R.V. Kamelin. This region crosses not only administrative boundaries, but also floristic boundaries, and the region's varied topography, coupled with the intersection of floristic boundaries, has led to a degree of endemism in the Altai flora (Orme et al., 2005).
The aim of this work was to study the taxonomy and characters of the Trollius species in the flora of the Altai Mountain Country. Firstly we identified diagnostic morphological characters of the Trollius species of the Altai Mountain Country, searched for new charactes for the identification of taxa, compiled the key for species identification, and analyzed the distribution of Trollius species in the AMC.

Results and discussions
We recognize three species of the genus Trollius within the AMC: T. asiaticus L., T. altaicus C.A. Mey, and T. dschungaricus Regel. Some important characters can be used to distinguish all three species (Figure 1, 2; Table 1). The margin of blades and the shape of teeth are significant characters for T. altaicus and T. dschungaricus. Trollius altaicus is characterized by short teeth, arcuate-convex along the edge, and acute or slightly obtuse at the apex. In contrast to T. altaicus, T. dschungaricus is distinguished by small pointed teeth. An important character crucial for species identification is sepal dimorphism (the shape of the sepal can differ in one and the same flower). Trollius dschungaricus and T. altaicus exhibit this character, whereas T. asiaticus has identical sepals. The most significant character for identification of the taxa is the length of the persistent style. Trollius altaicus has the longest persistent style, which distinguishes it from two other species. Trollius asiaticus grows in the wide range of habitats, and thus exhibits the morphological variability. Despite this, species is characterized by the constant features, such as thin, not fleshy consistence of blade of the leaf, rhombic shape of the basal leaf segments, spaced lobes of segments, oblong-triangular acute at the apex teeth with straight or slightly arcuate edges, sepals equal to petals, and very short persistent styles of follicles (in two other species, persistent styles are much longer). Interestingly, there are plants that combine diagnostic characters of T. altaicus and T. asiaticus leaves: lobes and teeth at the margin can sometimes be both straight and arcuate-convex on lateral sides, and the apex is pointed or acute. For T. dschungaricus, yellowish styles and stigmas are most characteristic, but sometimes they are dark-purple. Interestingly, there are plants that combine diagnostic characters of T. altaicus and T. asiaticus leaves: lobes and teeth at the margin can sometimes be both straight and arcuate-convex on lateral sides, and the apex is pointed or acute. For T. dschungaricus, yellowish styles and stigmas are most characteristic, but sometimes they are dark-purple. It can be assumed that this combination of characters indicates possible hybridization between different species in contact zones. It is important to note that the length of follicles and persistent styles are very different at the different stages of development due to the features of fruit morphogenesis. Three species exhibit elongated persistent styles at the initial stage of development, but during fruiting the length of the follicle increases more than the length of the persistent style (except for T. altaicus). The identification of plants collected at different phenological phases can be erroneous if this is not taken into account.
In three species studied, the flower buds and initial stages of the flower blooming are often characterized by various colors of sepals and petals: from pale yellow, dark yellow, and greenish to yellow-orange with tints of pink, reddish, and sometimes violet. These morphological characters are of an important diagnostic value and are used in this study to compile the identification key for the species studied.
The considered combinations of structural characters typical of different species are important for species identification. The causes of the morphological variability can only be clarified by further studies using different methods.
According to A. Doroszewska (1974), species of the genus Trollius from the Altai Mountain Country belong to two sections: Trollius (T. altaicus C.A. Mey., T. dschungaricus Regel), and Longipetala Dorosz. (T. asiaticus L.). The former is characterized by petals elongated, convex, thickened, shorter than sepals (Doroszewska, 1974), whereas the latter is distinguished by petals linear, flat, thin, longer than sepals. Trollius altaicus and T. dschungaricus belong to the same group, but exhibit a number of important differences. Trollius altaicus is mainly characterized by 5 segments of basal leaves (T. dschungaricus is distinguished by 3-5-lobed leaf blade), thin, not fleshy leaf blade consistence, often with the glossy surface (T. dschungaricus is distinguished by the thick, slightly fleshy blade, often with the glossy surface).
Molecular-phylogenetic studies do not cover all groups and most species (Despres et al., 2003;Wang et al., 2010). L. Despres et al. (2003) considered T. altaicus and T. asiaticus as belonging to the same clade and different sub-clades of the molecular-phylogenetic tree. W. Wang et al. (2010) analyzed T. asiaticus only; T. dschungaricus and T. altaicus were not investigated using molecularphylogenetic methods. Since all three species were poorly investigated by molecular methods, it is difficult to consider their taxonomic relationship and affiliation with certain groups.

Conclusion
The study of morphological characters of the Trollius species growing in the Altai Mountain Country allowed us to propose new characters of the leaves and flowers that were not previously used for the species identification: consistence of blade and degree of its dissection, type of margin, shape of teeth, number of petal veins, shape of nectarostigma, venation of follicles, and shape and direction of persistent style. The quantitative differences of the species are specified: length of the basal leaf petiole, number of sepals and petals, distance from the petal base to the nectarostigma, and length of persistent style. The suggested key based on a combination of vegetative and generative morphological characters allows us to identify species more accurately. As a result of the study, three species of Trollius were are identified for the Altai Mountain Country: T. altaicus, T. asiaticus, and T. dschungaricus; intermediate morphological forms, apparently of a hybrid origin, are detected.