Stipa ×fallax M. Nobis & A. Nowak, 2017

Nobis, Marcin, Nowak, Arkadiusz, Nobis, Agnieszka, Nowak, Sylwia, Żabicka, Justyna & Żabicki, Piotr, 2017, Stipa × fallax (Poaceae: Pooideae: Stipeae), a new natural hybrid from Tajikistan, and a new combination in Stipa drobovii, Phytotaxa 303 (2), pp. 141-154 : 145-151

Stipa ×fallax M. Nobis & A. Nowak nothosp. nov. ( Figs. 3 , 4 )

Type: ―Western Tajikistan, western Pamir Alai. Zeravshan Mts, high mountain steppe, on the southern slope of mountains (left slope of the Iskanderdarya River valley), ca. 0.6 km E of Serimadarun Lake (near Iskanderkul Lake), 39º05‘N / 68º23‘E, alt. 2340 m, incl. S, slope 5º, 15 June 2012, M. Nobis (holotype KRA 407904, isotypes KRA 407898 – 407902, Herb. Stip. M. Nobis).

Plant perennial, densely tufted, with a few culms and numerous vegetative shoots; culms 35–55 cm tall, 3–4-noded, glabrous or sparsely ciliate at the nodes and densely pubescent below them. Leaves of the vegetative shoots: sheaths densely pubescent, margins ciliate up to 1 mm long and with white edges; ligules (0.3–)0.5–2.0(–2.5) mm long, truncate, rounded or acute, densely ciliate with 0.5–1.5 mm long hairs on the apex and setulose on the back; blades convolute, grey-green, up to 34 cm long, (0.4–)0.5–0.8(–0.9) mm in diameter, adaxial surface densely long pilose with hairs 0.3–0.6 mm long, abaxial surface densely pubescent. Cauline leaves: sheaths densely pubescent, margins white and glabrous or shortly ciliate, shorter or longer than internodes, the upper ones at the culms up to 22 cm long, not inflated or inflated to a width 2.5–9.0 mm, glabrous or scabrous, rarely shortly pilose but only in the lower part, margins scabrous; ligules 0.5–4.0 mm long, rounded or acute, up to 1.5 mm long ciliate at the apex and setulose on the back; blades convolute, grey-green, up to 16 cm long, densely long pilose at the adaxial surface and pubescent at the abaxial surface. Panicle up to 20 cm long, contracted, with 8–18 spikelets, at the base or up to the half enclosed by the sheath of the uppermost leaf, branches erect, setulose, single or paired, with 1 or 2 spikelets. Glumes subequal, 50–61 mm long, pale green to straw-coloured, narrowly lanceolate, tapering into a long hyaline apex, at the dorsal line glabrous or sparsely setulose. Anthecium 11.0–13.0 mm long and 1.0– 1.3 mm wide. Callus 1.8–2.3 mm long, densely and long pilose on the ventral part, with hairs 1.9–2.4 mm long, on the dorsal long pilose with straight, sometimes with admixture of slightly falcate hairs, 1.2–1.7 mm long, occurring in the upper 3/4 of the callus length, at 0.2–0.4 mm below the base of lemma glabrous (sporadically with hairs occurring just below the base of lemma); base of the callus cuneate to slightly pyriform, peripheral ring 0.40–0.46 mm in diameter, acute, scar broadly elliptic to almost circular. Lemma pale green to straw-coloured, on the dorsal surface with abundant hooks and with 7 lines of ascending hairs 0.8–1.3 mm long, ventral lines terminates 1.5–2 mm below the top of lemma; dorsal line terminates in 3/4 of the lemma length, about 1.8–3.0 mm below the top; top of lemma somewhat scabrous due to hooks, prickles and short hairs, surpassed by a ring of unequal hairs 0.4–1.1(–1.3) mm long. Palea equalling lemma in length, without a dorsal line of hairs. Awn (109–)132–164(–176) mm long, unigeniculate or indistinctly bigeniculate; column (23–) 25–36 mm long, twisted, 0.5–0.6 mm wide at base, green or straw-coloured, sparsely and shortly pilose, hairs (0.1–)0.2–0.6(–0.8) mm long, increasing in length toward geniculation, at ca. 5–10 mm under geniculation with hairs 0.5–1.8(–2.0) mm long; seta flexuous or slightly falcate, (82–)102–130(–142) mm long and 3.1–4.2 times longer than column, hairs in the lower part of seta 4.8–6.3 mm long, gradually decreasing in length towards apex. Anthers purplish, 5.5–6.5 mm long, with up to 0.4 mm long ciliate on the apex. Ovary with 2 styles. Lodicules 3.

Additional specimens studied (paratypes): ― Western Tajikistan, western Pamir Alai. Zeravshan Mts , high mountain steppe, on the southern slope of mountains (left slope of the Iskanderdarya River valley ), ca. 0.5 km E of Serimadarun Lake (near Iskanderkul Lake), 39º05’N / 68º23’E, alt. 2300 m, incl. SW, slope 10º, 17 June 2010, M. Nobis ( KRA 431806 , 407903 ) ; Iskanderdarya River valley , Zeravshan Range B, Western Tajikistan, Pamir Alai Mts , Zeravshan Mts , high mountain stony steppe, on the left slope of Iskanderdarya River valley, ca. 0.7 km ESE of Serimadarun Lake (near Iskanderkul Lake), 39º05’05’’N / 68º22’51’’E, alt. 2300 m, incl. SW, 30 May 2015, M. Nobis & A. Nowak ( KRA 431821 , 431825 , 431826 ) .

Etymology: ―The name of the species originates from the Latin fallax (false, fallacious, fallible), because of its similarity to S. drobovii , S. ×alaica , S. ×hissarica and S. caucasica .

Distribution, population size and habitat ecology: ― Stipa ×fallax belongs to the Irano-Turanian element and the Middle Asiatic mountain sub-element. In the Iskanderdarya River valley S. ×fallax grows on loess substrate (pH=7.8), altitude 2250–2350 m, in plant communities of high mountain feather grass steppe on south-western slopes of mountains with exposure SW-S and inclination from 0 to 25°, ca. 1 km NE of the northern part of the Iskanderkul Lake. At this locality in 2015 we noted ca. 20 tufts of S. ×fallax scattered at the area of 0.02 km 2. The individuals of S. ×fallax were observed within feather grass steppe which, according to Nowak et al. (2016), belong to the Poo bulbosae-Artemision persicae alliance and the association of Stipetum lipskyi as well as in the transition zone between Stipetum lipskyi and Stipetum drobovii associations ( Fig. 5 ).

Below we present the phytosociological relevé documenting plot involving Stipa ×fallax .

Feather grass steppe, on the loess substrate, among stones, area of relevé 20 m 2, cover of herbs layer 30%: Stipa ×fallax 1, S. macroglossa subsp. macroglossa 2, S. caucasica 1, S. drobovii +, S. orientalis +, S. ×tadzhikistanica +, Achillea biebersteinii +, Allium sp. +, Artemisia persica 1, Bromus danthoniae 1, Bromus lanceolatus +, Bromus tectorum +, Carex stenophylloides 2, Ferula foetidissima +, Gagea ova +, Gentiana olivieri 1, Lepechinella sarawschanica +, Piptatherum songaricum +, Poa bulbosa 1, Pseudosedum sp. +, Tulipa turkestanica +, Valerianella oxyrrhyncha +, Veronica intercedens +, Ziziphora tenuior +.

High mountain steppes around the Iskanderkul Lake ( Fig. 5 ), are extremely rich in species of feather grasses. Besides Stipa ×fallax the following species were also recorded: S. ×alaica , S. arabica Trinius & Ruprecht (1842: 77) , S. ×brevicallosa Nobis (2013: 1340) , S. caucasica , S. drobovii var. drobovii , S. drobovii var. iskanderkulica , S. ×hissarica , S. hohenackeriana Trinius & Ruprecht (1842: 80) , S. kirghisorum Smirnov (1925: 232) , S. lipskyi Roshevitz (1916: 153) , S. macroglossa subsp. macroglossa , S. sareptana Becker (1882: 52) , S. orientalis Trinius (1829: 83) , S. richteriana Karelin & Kirilov (1841: 862) subsp. jagnobica ( Ovchinnikov & Chukavina 1956: 51) Tzvelev (1974: 14) , S. ×tadzhikistanica Nobis (2013: 1338) , S. turkestanica Hackel (1906: 59) subsp. trichoides ( Smirnov 1925: 233) Tzvelev (1974: 17) , S. ×tzvelevii , and S. zeravshanica Nobis (in Nobis et al. 2013: 667) ( Ovchinnikov & Chukavina 1957, Nobis 2013, Nobis et al. 2013, 2016).

Origin of Stipa ×fallax : ― Stipa ×fallax originated from hybridization between S. macroglossa subsp. macroglossa and S. drobovii . We consider this taxon as a hybrid because (1) it grows at a locality where populations of its putative parental species co-occur, and (2) its main macro- and micromorphological characters are intermediate in relation to characters of its putative parental species ( Fig. 3 , Table 5). The new taxon is similar to S. drobovii var. iskanderkulica ( Fig 3D ) in having densely pubescent blades of vegetative shoots at adaxial and abaxial surface; however, S. ×fallax differs from the latter taxon by longer ligules of the vegetative shoots, longer glumes, longer anthecia, longer calluses, longer awns as well as sparsely and shortly pilose awn columns ( Table 5). This new taxon differs from S. macroglossa subsp. macroglossa by having shorter ligules of vegetative shoots, shorter glumes, shorter awns, shorter setae, longer hairs on the dorsal part of the callus, scattered hairs at the top of anthecium, as well as pilose vs. glabrous awn columns ( Table 5).

Hybrid origin of Stipa ×fallax is also supported by the results of the pollen stainability analysis. Histochemical tests (e.g. acetocarmine, Alexander) used to assess pollen viability are useful and quick indicators of regular male meiosis. Dwarf, degenerated, non-stainable pollen grains clearly indicate abnormalities during microsporogenesis ( Dafni & Firmage 2000, Słomka et al. 2010). Hybrids generally have reduced frequency of stainable pollen grains as a result of disturbed meiosis, as shown in other genera like Solidago Linnaeus (1753: 878) and Viola Linnaeus (1753: 993) ( Kuta 1978, 1988, 1990, Migdałek et al. 2014). Individuals of S. ×fallax have a substantially lower frequency of stainable pollen grains compared to its parental species ( Table 3). Because histochemical tests should be combined with measures of pollen diameter due to the cytological imbalance often manifested by presence of pollen grains of different size ( Słomka et al. 2010, 2014), we also obtained pollen diameter data. Pollen grains of S. ×fallax are significantly smaller compared with both parental species, although the standard deviations of pollen grains diameter overlap in examined species ( Table 4).

Similar species: ―Having uni- or indistinctly bigeniculate awns, Stipa ×fallax is somewhat similar to other species of hybrid origin occurring in Central Asia, namely S. × alaica (= S. kopetdaghensis ), S. ×hissarica , S. ×manrakica and S. ×talassica (Nobis 2013, Nobis et al. 2015). However, Stipa ×fallax differs from them mainly in characters of indumentum of vegetative leaves and the lower part of the awn ( Table 6).

Morphologically Stipa ×fallax is also similar to S. caucasica s. l., but it differs from the latter in having longer ligules of vegetative shoots 0.3–2.5 (vs. 0–0.2) mm, sparsely short pilose column with hairs (0.1–)0.2–0.6(–0.8) mm (vs. densely short pilose with hairs (0.3–)0.5–1.5(–2.5) mm), inner surface of blades of vegetative shoots densely long pilose with hairs up to 0.6 mm (vs. densely short pilose with hairs up to 0.1 mm).

A new combination in Stipa drobovii : ― Ovchinnikov & Chukavina (1957) distinguished within Stipa bella Drobov (1925: 37) a variety “ S. bella var. incana Koroleva ” (in Ovchinnikov & Chukavina 1957: 421), nomen nudum. The taxon differs from the nominal variety by having leaves densely covered by short hairs. However, because the name of this taxon was not validly published, Tzvelev (1974), based on the same plant material, described S. caucasica subsp. iskanderkulica Tzvelev (1974: 20) , distinguished from the similar S. caucasica subsp. drobovii Tzvelev (1974: 20) based on character of leaves (densely pilose on both surfaces vs. abaxial surface glabrous, respectively). Three years later, Tzvelev (1976) wrote that S. caucasica subsp. iskanderkulica also has somewhat shorter awns (6–8 cm long) than S. caucasica subsp. drobovii (7–13 cm long), and five years later, Czerepanov (1981) elevated both taxa to the rank of species: S. drobovii and S. iskanderkulica (Tzvelev) Czerepanov (1981: 387) . On the other hand, Freitag (1985) treated S. caucasica subsp. drobovii and S. caucasica subsp. iskanderkulica as synonyms of S. caucasica subsp. caucasica , although the latter taxon differs significantly in the characters of its callus, anthecium, awn and leaves ( Fig. 1 ).

During our field studies in the Tian-Shan and Pamir Alai Mts, we found several dozen localities of S. drobovii and a dozen or so of S. iskanderkulica . The taxa often grow side by side at the same locality, and S. drobovii is more frequent. Our detailed examination of specimens of these two taxa shows they do not differ in any morphological characters ( Fig. 1 ) except presence or absence of short, dense hairs on outer (abaxial) surface of sheaths and leaves (sometimes, leaves are pubescent only on the lower part whereas on the upper part they remain glabrous). Therefore, we propose to reduce S. iskanderkulica to a variety within S. drobovii , similar to many other infraspecific taxa of Stipa that differ from the nominate varieties primarily by having pubescent leaves, such as S. orientalis var. ladakhorum M.Nobis in Nobis & Nowak (2016: 280), S. hohenackeriana var. grossheimii ( Tzvelev 1966: 21) Tzvelev (1974: 16) , S. arabica var. turgaica ( Roshevitz 1949: 21) Tzvelev (1976: 584) , S. ×brevicallosa var. hissarensis Nobis & Nowak (2016: 278) , S. richteriana var. dasyphylla ( Roshevitz 1916: 135) Tzvelev (1976: 578) and S. tianschanica subsp. gobica var. pubescens ( Hanelt & Davažamc 1965: 13) Nobis (2011b: 196) .

Figures

FIGURE 1. Biplot of principal component analysis (PCA) performed on 10 quantitative characters; ellipses indicate 95% confidence interval. For character abbreviations see Methods.

FIGURE 3. Micromorphology of Stipa drobovii (A–D), S.×fallax (E–H) and S. macroglossa subsp. macroglossa (I–L). (A, E, I) lemma surface - lateral view, (B, F, J) lemma apex, (C, G, K) callus, (D, H, L) adaxial surface of vegetative leaves. Abbreviations: h = hook, lc = long cell, sb = silica body, cc—cork cell, pr—prickle, mh—macrohair. Scale bars: C, G, K: 1 mm. Examined specimens of S. drobovii, S.×fallax and S. macroglossa were collected in Tajikistan (near Iskanderkul Lake) and are preserved at KRA.

FIGURE 4. Stipa ×fallax: (A) vegetative shoots, (B) awns, (C) anthecia, (D) panicle, (E) lower part of awns (columns) with anthecia. Scale bar: (A), (B), (D), (E) = 1 cm, (C) = 0.5 cm.

FIGURE 5. High mountain feather grass steppes near Iskanderkul Lake (Zeravshan Mts, Tajikistan), a habitat of Stipa ×fallax: (A) association of Stipetum drobovii, (B) association of Stipetum lipskyi, (C) Stipa ×fallax. Photos by M. Nobis, 30 May 2015.