Determination of the ecological areas of rare high-mountain <i>Ranunculus</i> species by indicator values methods
The indirect collecting of quatitative data on the rates of the main abiotic factors by the parameters of the vegetation opens up the possibility of identifying ecological ranges for poorly studied hard-to-reach species, especially rare high-mountain plants. The ecological plasticity of the genus Ranunculus L. in contrasting conditions of high mountains acquires the properties of adaptability, which contributes to the formation of endemic species. Therefore, a necessary aspect in addressing the issues of regional diversification of the genus Ranunculus is taking into account and assessing environmental factors as triggers of intrageneric ecological differentiation of the genus. The aim of the study is to test an indicator values method to determine the synecological areas of high mountain taxa Ranunculus akkemensis Polozhij et Revjakina (SeeFig. 1) and R. lasiocarpus C.A. Mey. (See Fig. 2) from the section Auricomus Schur., subsection Altimontana Schegol., endemic to the Altai-Sayan floristic province (ASP). To obtain the initial geobotanical material, we used the “Database of Siberian Vegetation (DSV)” computer database of releves of Siberian vegetation, registered in the international metabase “Global Index of Vegetation-Plot Databases” as AS-RU-002 and implemented in the integrated botanical information system IBIS v.7.2. All calculations with indicator values were performed in the gradient analysis module of this information system, alongside with combined taxonomic lists generation. MS Excel 2013 and Past v.3.26 software served as auxiliary tools for data preparation, statistical processing and visualization of results. Geographic location of the releves: Altai Republic: Seminsky, Kuraisky, Notrth-Chuisky ridges; Altai Krai: Tigirek ridge; Tuva Republic: Sangilen ridge. The source of the initial ecological information was the combined indicator value scales for Siberia by Ivan Tsatsenkin et al. (1974, 1978). These scales inherit the amplitude-optimum format of the indicator school by Leontiy Ramensky. Of the four available environmental factors, moisture (120-grade scale) and richness-salinity (nutrients availability, or fertility) of soils (30-grade scale) were selected as the most significant for the differentiation of ecotopes of mountain plants. The ecological characteristics of habitats, where these Ranunculus species were recorded, were calculated in accordance with the previously presented methodology: weighted averaging (by cover and environmental tolerance) of all indicator taxa in a releve; the cover of taxa was expressed in a 9-grade geometric scale. Individual species indicator value optima were calculated according to our published algorithm - as weighted averaging taking into account environmental consensus index, rarity of the scale’s grade in total sample, number of indicators per each releve. When compiling probabilistic ecological profiles for combined floras of coenoses with a selected taxon, an unimodal model was used, and the indicator value optimum statuses of indicator taxa were weighted by the sums of the percentages of their occurrence in such combined floras. Comparative analysis of the obtained values for the factors of soil moisture and fertility showed significant differences in the reaction of the coenotic environment of the model species to the level of these factors in habitats (See Fig. 3). Simultaneous mapping of phytocenoses with the participation of the studied species in the axes of soil moisture and fertility factors made it possible to assess and compare their ecological areas (See Fig. 4). The exact values of individual statuses (minimum, optimum, maximum) of the model species were calculated. When comparing the obtained quantitative parameters with earlier results of our ecological analysis of the genus Ranunculus in ASP, which took into account the confinement to a certain type of habitat and some morphophysiological properties of the species, the ecological characteristics of these species underwent changes. The results of the study enabled us to reasonably determine the belonging of R. akkemensis and R lasiocarpus to particular ecological groups, as well as to prove the efficiency of the indicator value correction method on relatively small samples of geobotanical data. The study for the first time allowed quantifying the ecological parameters of two rare alpine species of the genus Ranunculus according to the factors of soil moisture and nutrient availability. The paper contains 4 Figures, 1 Table and 16 References. Acknowledgments: The authors express their gratitude to colleagues who kindly provided their releves for our study: Eugeniy G. Zibzeev, Cand. Sci. (Biol.) (Central Siberian Botanical Garden, Siberian Branch of the Russian Academy of Sciences, Novosibirsk), Andrei I. Pyak, Dr. Sci. (Biol.) (Tomsk State University, Tomsk) and Igor V. Volkov, Cand. Sci. (Biol.) (Tomsk State Pedagogical University, Tomsk). The Authors declare no conflict of interest.