Predictive distribution for Salvia aethiopis (Lamiaceae) in Middle Asian Region based on climatic modelling

Geospatial investigation of distribution Salvia aethiopis L. (Lamiaceae) on the eastern limits of the range is p erformed using climatic modeling by MAXENT approach. Climatic conditions for the 33 local populations of the species as well as territories n ighbouring to them were examined in detail, using concepts of nestle-cells and a small polygone. According to obtained results, the most suitable cl imatic conditions are in only two small polygons (SP) around local populatio ns with coordinates 69.96E:42.48N and 70.03E:42.47N in central part of the area. They have 7.7 average points per a cell of 9.0 maximum. Other s ven SP have average points per a cell 7.1–7.3 (quite suitable c limatic conditions), all in the western part of the area, with coordinates from 66.69E to 67.69E and from 38.21N to 39.26N. High values of raw predictio n are in the locations with coordinates 70.97E:42.48N (0.123; Zhualyn Dist rict in Zhambyl Region, Kazakhstan), 70.03E:42.47N (0.063; Keltemash at, Tulkibas District, Turkestan Region, Kazakhstan), 67.09E:38.3 4 (0.063; Yuqori Machay, Surkhandarya Region, Uzbekistan), and 69.96 E:42.48N (0.054; Antonovka, Tulkibas District, Turkestan Region, Kaza khstan). These local populations of S. aethiopis should be assessed as the most likely secondary centers for further expansion of the species in the Middle Asian Region.


Introduction
The detailed study of the geospatial structure of the ranges of biological species is of great importance in the development of scientific measures for the protection of rare and endangered species, assessment of the state of the gene pool of resource species, determination of factors limiting the distribution of endemic taxa, solving issues of the genesis of genera and floristic complexes, investigation of dynamics of distribution of alien invasive species, and many other scientific problems [1].
Salvia aethiopis L. (Lamiaceae family) is а European-West Asian mountain-steppe species found in Central and Atlantic Europe, the Mediterranean, in the south of Ukraine, in the Republic of Moldova, Asia Minor, in the Caucasus, in Iran, and Middle Asia [2]. We have studied this species in the eastern limits of its distribution. There are numerous modern finds of this species in different parts of the region, confirmed by herbarium specimens and observations in nature, presented in special data base in internet, such as GBIF and iNaturalist, and our own observations (one of them is presented in Fig. 1).
The purposes of this research are the ecological multi-parameter assessment of the summar environmental situation in locations of S. aethiopis and around them, with determination the set of locations and neighbouring places where combinations of climatic variables are the most suitable to existing and developing local populations which can be secondary centers for futher expansion of the species in the Middle Asian Region.
To achieve these purposes, the following tasks were set: 1) to produce the series of models for the species distribution in the Middle Asian Region, using different output formats; 2) to create the protocol for assessing the levels of suitability of environmental conditions in lacations and around them; 3) to apply original concepts of a small polygone and nestle cells to estimation of suitability of environmental conditions; 4) range the most suitable locations and nestle cells; 5) determine the most likely secondary centers for futher expansion the area of the species in Middle Asian Region.

Material and methods
The study was performed for 33 local populations in the Middle Asian Region. Its coordinates are presented in the Table 1. Probablistic models for the distribution of the species in Middle Asian Region are constructed on climate layers imported from WorldClim, an international database of world climate, available at http://www.worldclim.org [3]. In the study, climatic data for 1970-2000 years were taken, including the period of S. aethiopis registration. According to experimental data and their expert assessment, the most informative models can be constructed with complete set of all available climatic variables [4,5].
The study has significant methodical significance. The procedure for multi-level assessment of the statement of the environment from least suitable to highly suitable is proposed and implemented in detail. If we use the default setting for adjust sample radius (zero value) in Advanced settings of Maximum Entropy Parameters, we will not be able to see and analyze the ecological differentiation in the cells around the locations. Reducing size of dots using negative values allow to analyze ecological situation in сells which are in contact with a location (so named the nestle cells).
In contrast to our previously proposed gradation of climatic suitability, which includes three levels [8], 9-level gradation was used in this study, which made it possible to more accurately differentiate the ecological situation between the cells of small polygons. Also, we offered to compose numerograms for small polygons [8]. Such numerograms show the levels of climate suitability in neighboring cells and find the best of them for plant reproduction.

Results
In accordance with the presence of hiatus, where local populations of this species have not been found, we propose to divide its range in the Middle Asian Region into three separate parts: western, central and eastern. In the global model obtained at 1/12 arc-degree resolution (near 50 sq. km in a cell), there are several zones highly suitable (red colored) and suitable (orange colored) for the species as well as territories with quite suitable climatic conditions (they having yellow and near yellow colors on plot files). Most of them are in the western and central parts of the regional distribution of the species, and only one small fragment of yellow color is in the eastern part of the area.
The western group of populations (Pamir-Alai) is the most numerous. It includes almost half of the counted localities -16 out of 33, and occupies the territory within the following limits: from 66.69E to 67.89E, and from 38.11N to 39.26N. The distance between neighboring populations in the western group usually does not exceed 20 km (Fig. 2). The eastern group consists of nine local populations, which are between 75.69E and 81.53E, 42.76N and 45.97N. The distance between neighboring local populations in the eastern group can exceed more than 60 km (Fig. 2B). The expertly calculated sum of points in small polygones varies from 13 to 61, and the average points are from 1.4 to 6.8, which corresponds to seven levels -from very low suitable to quite suitable environmental situation. Two local populations with coordinates 78.25E:42.81N and 78.47E:44.22N can be estimated as outliers.  The expertly calculated sum of points in small polygones varies from 13 to 61, and the average points are from 1.4 to 6.8, which corresponds to seven levels -from very low suitable to quite suitable environmental situation. Two local populations with coordinates 78.25E:42.81N and 78.47E:44.22N can be estimated as outliers.

Discussion
Generated models show that S. aethiopis has a high potential to expand its presence in the western and central parts of the species range in the Middle Asian Region. Eastern part is less suitable to distribute the species to other territories, with exception of the local population with coordinates 76.91E: 43.32N, which is in quite suitable conditions.