Alatavia pskemensis, Crespo, Manuel B., Martínez-Azorín, Mario & Mavrodiev, Eugeny V., 2017

Crespo, Manuel B., Martínez-Azorín, Mario & Mavrodiev, Eugeny V., 2017, New data on Iris pskemensis and its placement in Alatavia (Iridaceae), Phytotaxa 321 (3), pp. 294-298 : 294-297

Alatavia pskemensis (Rukš ā ns) M.B.Crespo, Mart.-Azorín & Mavrodiev comb. nov. ( Fig. 1A − G )

Basionym:— Iris pskemensis Rukš ā ns (2007: 363), ‘ pskemense ’ [≡ Iridodictyum pskemense (Rukš ā ns) M.B.Crespo, Mart.-Azorín & Mavrodiev (2015: 61), ‘ pskemensis ’]. Type:— UZBEKISTAN. Pskem Range, Ihnachsai [Ikhnachsay], stony slopes, 2500 − 3000 m elevation, 17 June 1998, Rukšāns & Seisums ARJA 9865 [plants cultivated ex hort., 20 April 2006, Rukšāns] (holotype GB-0048932 [digital image!] & GB-0049837 [digital image!], two sheets clearly labelled as being part of a single specimen; Art. 8.3 Ex. 4 of the ICN, McNeill et al. 2012) ( Fig. 2 ).

Description:—Plant 15–25 cm tall at anthesis. Bulb 2–3 × 1–2 cm, tuberiform, ovoid to oblong-ovoid, pale yellowish to whitish-cream; outer tunics, densely reticulate-fibrous, pale yellowish to whitish-cream; roots thin, fibrous, yellow; bulblets absent to few. Stem mostly underground at anthesis, inconspicuous, 1-flowered, unbranched, usually hidden among leaf bases and elongating somewhat in the fruiting stage. Leaves 2–4, 3–11 × 0.1–0.3(–0.5) cm, linear-lanceolate, subdistichous, usually shorter than the flower at anthesis and elongating later, glabrous, ± falcate, canaliculated with thickened margins, ± 3-ribbed on the abaxial side with the central rib forming a carina, rather pale grey-green above and green to glaucous-green beneath with minute papillate margins; they all clothed together at the base by a single membranous sheath (cataphyll) whitish to cream-coloured. Bracts 4.5–7 × 1–2 cm, subequal, tightly sheathing perianth tube, green to glaucous-green, membranous at margins, acute to acuminate, subcarinate. Perianth tube 3–4.5 cm long, fluxed with violet. Falls (outer perianth segments) 2.8–4 × 0.8–1.2 cm, erect to erect-patent, broadly lanceolate, subpandurate, smooth, reflexed towards the upper part, gradually tapering into a short claw; lamina (blade) 1.4–2 × 0.8–1.2 cm, oblong-lanceolate, acute, crenulate on margin, purple-violet (sometimes fluxed with white), mostly rimmed with a conspicuous narrow white band, and whitish at the basal half, fluxed with purple-violet; central ridge pubescent, yellow, rimmed with a narrow white band and reaching the central part of the blade; claw 1.5–2 × 0.3–0.5 cm, pubescent, with whitish and yellowish veins and fluxed with purple-violet. Standards (inner perianth segments) 3.5–5 × 0.4–0.6 cm, erect, oblanceolate, entire, subacute, pale bluish or rarely whitish, with a dark blue to violet central band; haft canaliculated, ca. 1 cm long, dark blue to violet, with one short tooth on each side near the base. Style branches 2.4–2.7 cm, linear-oblong with the lobes 1.2–1.5 × 0.1–0.2 cm, linear, acute, ± recurved backwards; stigma semicircular, entire (not bilobed) or inconspicuously notched, ± undulate on margin. Stamens 1.3–2 cm long, glabrous; anthers 0.8–1 cm long; filaments 0.5–0.8 cm long. Capsule 2.5-4.5 cm long, ellipsoid-cylindric, papyraceous, narrowed into a basal stalk up to 2 cm long, and with apical beak up to 4.5 cm long; seeds 3.5–4.7 mm, subglobose, reddish-brown, non-arillate; testa surface irregularly wrinkled.

Phenology:—Flowering in June–July. Plants cultivated in Latvia flower in April.

Etymology:—The specific epithet refers to Pskem ( Uzbekistan), the land where it was found.

Distribution:—This species appears to be restricted to the high elevation (alpine) areas of Ihnachsai (Ikhnachsay), near Sjemesas, in the Pskem mountain range (eastern Uzbekistan), and makes it the westernmost known species of the genus. However, Alatavia pskemensis could also be found in the neighbouring areas of Itelgesay, in the upper course of river Angren or Achangaran (ca. 60 far southwards from the type locality), according to comments by Tscherneva (1971: 140) who studied some incomplete herbarium materials from that area she attributed with doubt to its close relative, very rare A. winkleri (J. Rukš ā ns, pers. comm.). That distribution is entirely compatible with the range attributed to the genus Alatavia by Crespo et al. (2015), and also supports its exclusion from Iridodictyum Rodion. , a genus occurring from Turkey and the Transcaucasus to the Middle East.

Habitat and ecology:— Alatavia pskemensis grows in rocky slopes at ca. 2500–3000 m elevation, in an area where other interesting bulbous plants such as Juno coerulea Poljakov (1958: 250) (≡ Iris albomarginata Foster 1936: 42 ), Tulipa aff. kaufmanniana Regel (1878: 194) or Tulipa aff. turkestanica Regel (1875: 296) are found.

Taxonomic relationships:—Morphological features of the cataphyll, leaves and flowers ( Figs. 1 & 2 ) suggest close relationships of Iris pskemensis to Alatavia , as previously pointed out by Hall (2013). This genus was described by Rodionenko (1999) to group two Central Asian species, A. winkleri and A. kolpakowskiana , occurring in the western parts of Tien Shan range, where Kazakhstan and Kyrgyzstan meet ( Rodionenko 2013, Crespo et al. 2015). Conventional molecular phylogenies as well as the three-taxon statement analysis of the molecular data placed A. kolpakowskiana as the sister group of the ‘ Xiphion clade’ ( Iris subg. Xiphium sensu Wilson 2011 ), which also included Xiphion Miller (1754 : without pagination) (‘Spanish irises’), Syrianthus Crespo et al. (2015: 62) (‘Syriacae irises’), Iridodictyum (true ‘Reticulata irises’), and Hermodactylus Miller (1754 : without pagination) (‘Widow irises’) (cf. Tillie et al. 2000, Wilson 2011, Mavrodiev et al. 2014, Crespo et al. 2015). That basal position is congruent with morphology, since Alatavia kolpakowskiana and A. winkleri show a bulb structure like that of Iridodictyum and the leaves resembling those of Xiphion (cf. Hall et al. 2000). However, integrative evaluation of morphological, molecular and biogeographic data is consistent with segregation of Alatavia as a proper genus ( Mavrodiev et al. 2014, Crespo et al. 2015).

Regarding the internal relationships of Alatavia , no comprehensive molecular information is available so far, and therefore only morphological connections can be discussed here. Beside the combination of characteristics mentioned above as diagnostic for Alatavia , all three species in the genus also share the presence of two teeth or short lobes near the base of the standard haft ( Fig. 1E ), an uncommon character absent in other members of the ‘ Xiphion clade’ which can also be considered a standard synapomorphy of Alatavia . This peculiar feature was stressed in the protologue of A. kolpakowskiana by Regel (1878) and illustrated later by Baker (1880) from plants grown in London.

Other remarkable features, however, allow easy separation of all three concerned species. On the one hand, A. winkleri was described to produce bulbs with membranous (not reticulate-fibrous) outer tunics, an unusual character among the ‘Reticulata irises’ that Dykes (1912) and Mathew (1989a,b) suggested that was deduced after studying herbarium material with incomplete bulbs. This character was argued by Regel (1883) and Fedtschenko (1935) to place it as a member of Iris sect. Xiphion (Mill.) Tausch (1823 : without pagination). However, observations on living plants grown in Latvia (J. Rukš ā ns, pers. comm.) allow us to confirm that those outer tunics of A. winkleri show prominent longitudinal ribs, which are not evidently reticulate-fibrous, and also bulbs are white. These are diagnostic differences with regard to A. pskemensis and also A. kolpakowskiana (see below). Furthermore, they can also be easily differentiated from the typical A. winkleri on account of its minute papillate falls which are wider than the standards, and the blade of falls acute to acuminate, milky-white in the basal half (only fluxed with purple-violet). However, both A. winkleri and A. pskemensis grow in similar ecological environments between 2500–3000 m elevation, though the latter occurs in eastern Uzbekistan, ca. 400 km far westwards from the known localities of A. winkleri . Accordingly, and despite comments by some authors ( Dykes 1912, Rodionenko 1961, Mathew 1989b) about its doubtful taxonomic value, A. winkleri is here accepted as a proper species.

On the other hand, A. kolpakowskiana is morphologically closer to A. pskemensis on the basis of its vegetative and floral characteristics. Among the common features, both species produce densely reticulate-fibrous tunics and yellow-coloured bulbs (both characters absent in A. winkleri ). However, some differences support their separation. Bulbs are bright yellow in A. kolpakowskiana , whereas they are pale yellowish to whitish-cream in A. pskemensis ( Fig. 1F ). The perianth tube is longer and the standards are wider (0.6–1.5 cm vs. 0.4–0.6 cm) in A. kolpakowskiana , whereas the blade and central ridge of falls are bordered with a conspicuous white band in A. pskemensis ( Fig. 1A–C ), which is lacking or inconspicuous in A. kolpakowskiana . Furthermore, A. kolpakowskiana grows in different habitats, between 800–1300 m elevation ( Mathew 1989a,b), and ca. 550 km far eastwards from the type locality of A. pskemensis to about 60–100 km in the nearest known populations in Taskent area (J. Rukš ā ns, pers. comm.).

According to the extant information, the separation of those three species is favoured here. Nonetheless, further fieldwork is needed to discover new locations of Alatavia pskemensis , as well as of A. kolpakowskiana and the rare or almost extinct A. winkleri , to obtain additional morphological and molecular data which help to clarify the connections among taxa of Alatavia .

Figures

FIGURE 1. Alatavia pskemensis. A) Habit of several plants, showing the single basal cataphyll; B) Detail of a bluish-flowered plant; C) Detail of a whitish-flowered plant; D) Detail of the semicircular stigma (arrow); E) Haft of inner standard showing a short tooth near the base (arrow); F) Bulb and the reticulate-fibrous outer tunic; G) Detail of four seeds and a beaked fruit with spathes. Scale bars = 1 cm. (Photos A−E: Janis Rukšāns).

FIGURE 2. Holotype of Alatavia pskemensis (GB-0048932 & GB-0049837, both marked as part of a single specimen). Reproduced with permission of the herbarium Gothenburg (Sweden).