Atlas Florae Europaeae notes, 33. Taxonomic synopsis of East European species of the Cytisus ratisbonensis group (Fabaceae) Author Sennikov, Alexander N. https://orcid.org/0000-0001-6664-7657 Botanical Museum, Finnish Museum of Natural History, University of Helsinki, Helsinki 00014, Finland alexander.sennikov@helsinki.fi Author Tikhomirov, Valery N. https://orcid.org/0000-0003-1822-0557 Belarusian State University, Minsk, Belarus text PhytoKeys 2024 2024-02-23 238 157 197 http://dx.doi.org/10.3897/phytokeys.238.118031 journal article http://dx.doi.org/10.3897/phytokeys.238.118031 1314-2003-238-157 6E20579249075578A87DB4839405813A 9. Cytisus lithuanicus Gilib., Hist. Pl. Europe 2: 275 (1798) - Chamecytisus ratisbonensis auct.: Tzvelev (1987) ; Fedoronchuk (2022) . Type . Belarus . Brest Region , Kobrin District. Vicinities of Verkholesie Village , sandy hills with pines, 29.05.1979 , D.I. Tretiakov & N.V. Kozlovskaya ( neotype MSK, designated here; isoneotypes MSK, MSKU). Fig. 9 . Figure 9. Neotype of Cytisus lithuanicus Gilib. Description. Upright shrubs with basally prostrate stems up to 40(60) cm tall and short branches. Leaves with obovate leaflets, glabrous above, with appressed hairs 0.4-0.6(0.8) mm long below, petioles sparsely to densely covered with laxly appressed hairs. Flowers strictly lateral, 1-4 in axils, on pedicels 5-10 mm long, pale yellow; calyx 12-14 mm long, with laxly appressed hairs 0.6-0.8 mm long; standard broadly elongate, glabrous above. Distribution. Europe: Poland, Belarus, Ukraine. This is the first attempt to circumscribe the distribution area of this species. Ecology. The species occurs in margins of dry pine and mixed forests. Chromosome counts. 2n = 100 ( Parfionaŭ et al. (1975) , as Chamaecytisus sp.); material collected from native populations in Brest Region of Belarus; vouchers at MSK. Notes on nomenclature. The first name intended for this species, Cytisus pubescens Gilib., was originally introduced in Gilibert (1781) , which is included in the list of suppressed works for species and infraspecific taxa, but validly published in a revised version of the same book ( Gilibert 1793 ), which is not suppressed for nomenclatural purposes. Its intended replacement name, C. lithuanicus , was validly published in a generally accepted work of the same author ( Gilibert 1798 ). Although the protologue of C. lithuanicus essentially recapitulated the information from the protologue of C. pubescens , it included no reference to the latter, whereas one of its elements, the illustration of Cytisus VII ( Clusius 1601 ), was no longer considered taxonomically identical to the plants observed by Gilibert. As a result of these changes, C. lithuanicus is not a superfluous replacement of C. pubescens . Gilibert (1781 , 1798 ) provided an extensive morphological description of the species, which was poorly understood by subsequent authors because of the uncertain taxonomy of Cytisus in Belarus and Poland ( Syreitschikow 1912 ; Kreczetowicz 1940 ). In eastern Poland and western Belarus, four species of C. sect. Tubocytisus may occur: octoploid ( C. lithuanicus in our work), tetraploid ( C. cinereus and C. ruthenicus ) and diploid ( C. polonicus ) ( Sennikov and Tikhomirov 2024a ). To understand which of these four species was described by Gilibert, we compared the diagnostic characters extracted from the protologue of C. lithuanicus with the characters used as diagnostic in our work (Table 2 ). Table 2. Comparisons of selected diagnostic characters from the protologue of Cytisus lithuanicus ( Gilibert 1781 , 1798 ), interpreted using Stearn (1983) , with those of C. lithuanicus , C. polonicus and C. ruthenicus (this work).

Characters / species	C. lithuanicus , protologue	C. cinereus	C. lithuanicus , our work	C. polonicus	C. ruthenicus
Habit	"frutex basi decumbens sed rami erecti"	erect, basally ascending, not prostrate	basally prostrate, with erect branches	prostrate	erect
Plant height	"pedalis & cubitalis" = 30-45 cm	up to 40-60(80) cm	up to 40(60) cm	up to 20 cm	up to 120(200) cm
Calyx length	"sex linearum" = 13.5 mm	11-14 mm	12-14 mm	(7)8-10 mm	10-12 mm
Peduncle length	"vix quator linearum" = less than 9 mm	3-5 mm	5-10 mm	3-5(7) mm	5-7 mm

The habit of C. lithuanicus described in the protologue agrees with the octoploid species, whereas the match with C. ruthenicus (tall erect shrub) is impossible and the correspondence with C. polonicus (prostrate shrub) is less likely. The most important character is the calyx length, which immediately rejects C. polonicus (shortest calyces), but perfectly matches the octoploid (longest calyces). The peduncle length also disagrees with C. polonicus , which typically has shorter pedicels (subsessile flowers), whereas the octoploid plants usually have longer pedicels (lax flowers). Cytisus cinereus is similar to the plant described by Gilibert in the calyx length, but its stems are usually taller and pedicels are shorter; besides, the pubescence on the calyces of C. cinereus is long and laxly appressed to subpatent, and is usually perceived as golden-coloured because of its length and density ( Kreczetowicz 1940 ; Heywood and Frodin 1968 ; Tzvelev 1987 ), whereas the calyces of C. lithuanicus were described as "albescens" , thus indicating a shorter and sparser pubescence like in the octoploid plants. All these characters strongly indicate that the only species corresponding to the protologue of C. lithuanicus can be the octoploid, for which we resurrect this species name here. Cytisus lithuanicus was described from the western vicinity of Bialystok (present-day Poland), which was part of the Grand Duchy of Lithuania at the time of description. The original material was missing in the personal herbarium of Gilibert (KW) already by the beginning of the 20th century ( Syreitschikow 1912 ; Shiyan et al. 2013 ). In the absence of any material suitable for lectotypification, we designate as neotype a specimen matching the original description and belonging to the population which was caryologically tested. Notes on taxonomy and distribution. This species was formerly included in C. ratisbonensis ( Kreczetowicz 1940 ; Zielinski 1975 ; Tzvelev 1987 ) because of its morphological similarity. Cytisus lithuanicus differs from C. ratisbonensis and C. polonicus by its upright stems, and also from the latter species by its longer calyces (12-14 vs. (7)8-10 mm long) and pedicels (5-10 vs. 3-5(7) mm long).