Additions to the vascular flora of the Tyumen region, Western Siberia

The article contains information on five species and three hybrids (Potamogeton × acutus, Potamogeton × pseudolacunatus, Stuckenia chakassiensis × S. macrocarpa) of vascular plants new to the Tyumen Region; seven of them are hydrophyte and one is a semi-aquatic species. We provided the occurrence data on 37 plant species not previously known in examined administrative districts of the Tyumen region, including four protected (Cypripedium macranthos, Pedicularis dasystachys, Ranunculus silvisteppaceus, Zannichellia repens) and four alien species (Elodea canadensis, Galega orientalis, Impatiens glandulifera, Phragmites altissimus).


Introduction
Botanical studies conducted annually in the Tyumen region provided new information on the floristic richness of this territory. This article is a serial continuation of author floristic publications, based on botanical research from Tyumen region, Russia. We provided data on species and hybrids of vascular plants new to the region and not listed in the "Determinant of the Vascular Plants of the Tyumen Region" (Glazunov et al. 2017). In addition, we provide information on rare plant species locations in studied administrative districts, where they were not previously known (Glazunov et al. 2017), including protected (Yakushev VV 2017) and alien species in the Tyumen region.

Material and methods
This research is based on author data obtained during the field work in vegetation periods of 2015-2019 and study of herbarium specimens stored in the Tobolsk complex scientific station of the Ural branch of the Russian Academy of Sciences (TCSS UB RAS, Tobolsk). In addition, we examined more than 140 herbarium sheets on Potamogetonaceae family from the private herbarium of I.V. Kuzmin (Tyumen State University, Tyumen). The author collected and identified the herbarium specimens cited in the article; otherwise, the name of the collector was indicated. We follow S.K. Cherepanov (1995) for the taxonomy and plant names. For some taxa (Potamogeton and Stuckenia) the modern processing was taken into account (Papchenkov 2001;Kaplan 2008), the brief comments were also provided for some species. We presented the locations of cited species and hybrids new to the Tyumen region, as well as protected and alien species (Fig. 1).
The herbarium specimens cited in this article are stored in the herbarium of the TCSS UB RAS. Some of the doublet samples were transferred to the herbarium of the Papanin Institute for Biology of Inland Waters RAS (IBIW), as was indicated in the label citation.
Note. This species differs from closely related Potamogeton alpinus Balb. by its smaller and narrower leaves (Papchenkov 2007).   ; Lake Suponnoe, shallow water off the SE shore; salinity of the water is 0.3 g/l; 30 Jul. 2019 (Fig. 1).
The species is protected in the Tyumen Region (Yakushev VV 2017). In recent years, Z. repens is apparently expanding its area to the north and was recently found in the territory of Tobolsk (Kapitonova 2018).
Note. This species differs from the closely related Stellaria palustris Retz. by its narrow green leaves, shorter sepals and petals and the presence of small acute tubercles in the lower part of the stem (Tzvelev 2000(Tzvelev , 2004.  in a lake with shallow water; 21 Jul. 2018; V.I. Kapitonov leg. • 400 m S of village Bajgara; 58.0236°N, 68.8440°E; lake in the floodplain of the Irtysh River with shallow water on the east shore; 3 Jul. 2019. • 300 m S of village Bajgara; 58.0246°N, 68.8442°E; lake at the right bank of the Irtysh River, shallow water off the shore; 3 Jul. 2019 (Fig. 1).
Note. There are three specimens with flowers. This species differs well from its closely related Utricularia vulgaris L. based on the following characters: corolla with lower lip flat and spreading margins, palate without hairs (Taylor 1989) and some additional characters such as, the long straight pedicels, slightly deflected from the peduncle, being three or more times longer than the bracts, free anthers not intergrown with each other, and the curved S-shaped stem (Tzvelev 2000;Lisitsyna et al. 2009) (Fig. 3). This species is characterized by some environmental preferences. So, it was revealed that U. australis grows in warm (~ 26 °C), alkaline (pH 8.3 median value) and shallow (< 20 cm) waters (Ceschin et al. 2020). The examined species grows in the European part of Russia (Tzvelev 2000;Lisitsyna et al. 2009), including those specimens found in the southern regions (Astrakhan region) (Kapitonova et al. 2011) and in the Vyatka-Kama Cis-Urals (Kapitonova 2015). For Western Siberia, the species was not previously recorded (Lisitsyna and Papchenkov 2000;Doron'kin 2012).
Note. There is one specimen without flowers. This species differs from the closely related Utricularia intermedia Hayne by the presence of single vesicles on green photosynthetic leaves and by the pointed segments of green leaves (Taylor 1989;Lisitsyna and Papchencov 2000). For Western Siberia, the species was not previously recorded (Lisitsyna and Papchenkov 2000;Doron'kin 2012).
New records of some rare species have been documented in areas that were not previously known to occur within the studied administrative districts of Tyumen region (Glazunov et al. 2017). Note. The species is protected in the Tyumen Region (Yakushev VV 2017). In the cited localities, plants with both the typical pink-flowered form and the less common white-flowered form of the plant are found ( fig. 4).  (Fig. 1, 5).

Plantago cornuti
Note. The species is protected in the Tyumen Region (Yakushev VV 2017). This is the second location of the species in the region (Glazunov et al. 2017).

Conclusion
We revealed five species and three hybrids of vascular plants new to the Tyumen region. Seven taxa are hydrophytes and one species is a semi-aquatic plant. Our study also provides data on 37 plant species occurrence in the administrative districts of the Tyumen region, where they were not previously known. This list includes four regional protected species (Cypripedium macranthos, Pedicularis dasystachys, Ranunculus silvisteppaceus, Zannichellia repens) and four alien species (Elodea canadensis, Galega orientalis, Impatiens glandulifera and Phragmites altissimus).