Using marginal species localities for the revision of the western boundary of the Altai-Yenisei floristic Province

Floristic regionalization is a necessary stage of the investigation of plant taxa distribution. The result of floristic regionalization is a scheme of geographic units (phytochoria), which differ by composition and structure of their floras. There are several approaches to distinguish phytochoria and their boundaries: by geographical features of the investigated territory; by vegetation and taking into account the relief of the territory; by endemic taxa; by comparing the floras of the key territories; by concentration of range boundaries and by lines of the range boundaries coincidence. For drawing phytochoria boundaries, this paper proposes to use the westernmost and the easternmost species localities on dot distribution maps and clusters of these localities rather than ranges and concentrations of range boundaries. The research specifies the western boundary of the Altai-Yenisei floristic Province (WbAYP). Published dot distribution maps of 2569 vascular plant species and subspecies of Siberian flora were used to reveal marginal western and eastern localities. They were geocoded by means of Geographic Information System ArcView GIS 3.2a (registration number is 843181116338) and the module ArcView Spatial Analyst 2.0a (registration number is 849601104159). The coordinates of geocoded localities and supplementary data (taxon name, numbers of map and locality) were entered into the Localities Database tables in MS Access (DBLoc). The total number of entries in the database tables was 169854. The marginal western and eastern localities in the limits of 49°-62°N and 80°-100°E were selected for each species/subspecies from the DBLoc. The latitudinal extent of the frame corresponds to the latitudinal length of the WbAYP, and the longitudinal extent corresponds to the distance of approximately 10° to the west and to the east from the border. Selection of the marginal localities was made by means of computer programmes written by the author in the Visual Basic for Applications. At this stage, the Marginal Localities Database was made (DBMarLoc), which comprised data on 1654 dots. Then, for more detailed consideration of the southern, central and northern parts of the boundary, data corresponding to the localities from smaller overlapping frames along the boundary were selected (See Fig. 1). GIS NextGIS QGIS was used to visualize some floristic boundaries in Asiatic Russia. The R free software environment for statistical computing and graphics was used to visualize marginal localities inside the selected frames, as well as to test their patterns against Complete Spatial Randomness (CSR) hypothesis. CSR hypothesis was tested by x² test (quadrat.test function in spatstat package in R). Southern part of WbAYP. Testing CSR hypothesis for marginal localities in frame 1 (827 dots, a grid of 10x4 squares with side of 1°) (See Fig. 2) gives thep-value less than 2.2e-16, that is less than 0.001 and allows us to reject the null hypothesis of complete spatial randomness of the distribution of dots in the frame. The deviation from the random distribution of marginal localities is manifested in their accumulation in the southwestern part of the frame, corresponding to the Altai Mountains. The dot cluster extends beyond the westernmost point of the Altai-Yenisei Province at 84°E. There, at the Tigerekskiy Ridge, there are the westernmost Siberian localities of Schulzia crinita (Pall.) Spreng., Lloydia serotina (L.) Rchb., Salix vestita Pursh, Minuartia biflora (L.) Schinz et Thell., Smelowskia calycina (Stephan) C.A. Mey., Saxifraga terektensis Bunge, Sibbaldiaprocumbens L., Hedysarum theinum Krasnob., and Doronicum altaicum Pall. Obviously, the Altai-Yenisei floristic Province should include the Western Altai Mountains of Altai Krai and the province boundary shoud be located more to the west than that drawn earlier. Central part of WbAYP. Testing CSR hypothesis for marginal localities in frame 2 (52 dots, a grid of 6x4 squares with side of 1°) gives the p-value 0.045, that is less than 0.05 and does not allow us to accept the null hypothesis of complete spatial randomness of the distribution of dots in the frame. However, attention is drawn to the closeness of the p-value to the threshold level, the excess of which would allow accepting the random distribution of dots in the frame. Testing CSR hypothesis for marginal localities in frame 3 (128 dots, a grid of 4x6 squares with side of 1°) gives the p-value of 6.237e-10, that is less than 0.001 and allows us to reject the null hypothesis of complete spatial randomness. The cluster of marginal localities in coordinates 52°-53°N and 89°-90°E corresponds to the Abakan Ridge and ridges of smaller scale at the junction of the Abakan Ridge and the Western Sayan Ridge at the southern part of the Republic of Khakassia. There, the marginal localities of Aconitum biflorum Fisch. ex DC., Oxytropis kusnetzovii Krylov et Steinb., and Conioselinum longifolium Turcz are found. The cluster of dots in coordinates 54°-56°N and 89°-91°E corresponds to the northern part of the Republic of Khakassia with its western boundary approximately along the meridian 89°E by the slopes of the Kuznetsk Alatau Ridge. The marginal western localities are found there of Salix saxatilis Turcz. ex Ledeb., Betula divaricata Ledeb., Veronica alpina L. s. str. Apparently, WbAYP in its central part should be delineated approximately along the 89°E meridian. Northern part of WbAYEP. Testing CSR hypothesis for marginal localities in frame 4 (56 dots, a grid of 15x5 squares with side of 1°) gives the p-value of 0.11, that is more than 0.05 and allows us to accept the null hypothesis of complete dot spatial randomness in the frame. Comparatively small number of marginal dots and their random distribution does not allow us to outline floristic boundary by marginal localities in this region. Nevertheless it is noteworthy that some marginal localities tend to the Ob’ and Yenisei Rivers and their tributaires. Apparently, the northern part of the WbAYP should be drawn according to the geographical principle by the Yenisei River, which flow among plain and mountain territories: the Yenisei and Ketsko-Tumskaya plains to the west of the river, the Yenisei Ridge and Zaangar Plateau to the east of it. For example, the marginal western localities of Lilium pensylvanicum Ker-Gawl., Filipendula palmata (Pall.) Maxim. and Chrysanthemum zawadskii Herbrich subsp. peleiolepis (Trautv.) Zuev. are marked for specified meridional interval to the east of the Yenisei River. The paper contains 2 Figure and 27 References

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