Loncomelos visianicum (Tomm. ex Visiani 1876: 176 ) Speta (2001: 172)

Bogdanović, Sandro, Brullo, Salvatore, Ljubičić, Ivica, Rat, Milica & Salmeri, Cristina, 2020, Cytotaxonomical remarks on Loncomelos visianicum (Hyacinthaceae), a poorly known species endemic to Croatia, Phytotaxa 430 (2), pp. 95-108 : 98-102

Loncomelos visianicum (Tomm. ex Visiani 1876: 176) Speta (2001: 172) ( Figs. 1 , 2 )

Basionym:― Ornithogalum visianicum Tomm. ex Visiani (1876: 176) . Type (lectotype, designated here):―[Icon.] tav. I, fig. I. ( Visiani 1876); epitype (designated here):― Ornithogalum visianicum Tommas. In ins. Pelagosa contra ins. Lesina Dalmatia, Stossich prof. Ad, s.n. (PAD HD01481!).

Perennial plant. Bulb epigeous, usually aggregated, 30–60 × 20–50 mm, subconic, truncate at the base, with peripheral roots; outer tunics brownish. Leaves green, slightly pruinose, uniformly colored, glabrous, (3–)4–7, in a basal rosette, 28–80(–90) cm long, 6–22 mm width, canaliculate, cucullate at the apex, proteranthous, often dried at the anthesis. Floral stem 30–45 cm long (excluding the inflorescence), erect, smooth, green. Inflorescence racemose, cylindrical, 12–20(–25) cm long, with 12–25 flowers; bracts membranous, 5–10 × 2–3.5 mm, 3–7–nerved, shorter than pedicels, ovate-lanceolate, with apex acuminate; floral pedicels erect-patent, 8–15 mm long, the lower ones usually longer; fruiting pedicels erect and appressed to the stem. Flowers 20–22 mm in diameter; tepals patent, smooth at the margin, whitish, tinged with pale yellow in the adaxial side, with a central yellowish-green band in the abaxial side, 5-nerved, rolled up when mature; outer tepals elliptical-lanceolate, cucullate at the apex and ending with a thickened appendix, 10 × 4–4.2 mm, slightly canaliculate; inner tepals oblong-elliptical, rounded to slightly retuse at the apex, usually with a short mucro, 10 × 5.4–6 mm, markedly canaliculate. Stamens erect, slightly shorter than tepals; filaments white, 6 mm long, abruptly widened and thickened in the basal half, which is 2.4–2.5 mm wide in the outer stamens and 3–3.5 mm wide in the inner stamens; anthers dorsifixed, yellow, 4.8–5.2 mm long. Ovary yellowish-green, smooth, shining, ovoid, 3–4 × 2.5–3 mm, truncate at the apex, trigonous; style whitish, filiform, 3–3.5 mm long; stigma trilobed, papillose. Capsule 10–12 × 8–9 mm, ovoid, trigonous. Seeds not seen.

Karyology:—The somatic chromosome number of Loncomelos visianicum is 2n = 42 ( Fig. 3A ) with or without accessory chromosomes. Based on the chromosome arrangement observed in all the investigated samples, this species is triploid with a basic number x = 14. The karyotype is characterized by 14 triplets ( Fig. 3B ), distinct as big-sized and small-sized (less than 5 µm in length), as also highlighted by the values of different symmetric indices ( Table 2). Four triplets are metacentric (2 big-sized and 2 small-sized), 1 meta-submetacentric (showing arm ratio exceeding 1.30), 6 were submetacentric (3 big-sized and 3 small-sized), and 3 were subtelocentric. Thus, the chromosome formula can be expressed as 2n = 3x = 42 = 12 m + 3 msm + 18 sm + 9 st + 0–5 B. The longest chromosome was 13.0 ± 2.3 µm long and the shortest one was 1.61 ± 0.3 µm long, with a mean chromosome length of 5.44 ± 2.8 µm. Relative chromosome length varied from 5.7% ± 0.4 to 0.71% ± 0.1. Arm index varied on average from 1.16 to 4.1, while the centromeric index ranged from 46.3 to 19.6. Terminal satellites were occasionally detected in the short arms of some subterminal chromosomes in triplets IV and IX. In addition, 2–5 B-chromosomes (less than 1.5 µm long) were observed in some of the measured mitotic plates.

Leaf anatomy:—According to literature ( Wittmann 1985, Tornadore 1985, 1986, Tornadore & Orza 1987, Lynch et al. 2006, Peruzzi et al. 2007), Loncomelos species are characterized by leaves uniformly coloured, canaliculate, with a dorsiventral structure, smooth in the adaxial surface and ribbed in the abaxial one, showing at the margin epidermal cells covered by a thickened cuticle, palisade tissue distributed along the whole perimeter and spongy tissue occupying the inner part. There are two types of vascular bundles arranged in two rows along the mesophyll; larger vascular bundles are usually distributed in the central part of the mesophyll, alternating with smaller ones sorted towards the abaxial side. The larger bundles are interspersed with mucilage cells that in the mature leaves are replaced by rhexigenetic lacunae. Loncomelos visianicum leaves show a variable size, the largest ones are characterized by ca. 40 large vascular bundles, interposed among lacunae; these bundles decrease in number in the progressively narrower leaves up to a minimum of ca. 13, while the number of small vascular bundles coincides with that of the mesophyll lacunae ( Fig. 1 M–N ).

Phenology:—Flowering from April to late May, fruiting from late May to June.

Distribution and habitat:—Currently, this species occurs only in few stands on the island of Velika Palagruža, where it is localized in the maquis dominated by Euphorbia dendroides Linnaeus (1753: 462) , mixed with Olea europaea Linnaeus (1753: 8) subsp. sylvestris ( Miller 1768: n. 3) Rouy ex Hegi (1927: 1936) and Artemisia arborescens Linnaeus (1763: 1188) . It grows in rocky places represented by Triassic dolomites, often associated with other endemic species, such as Aurinia leucadea ( Gussone 1826: 268) Koch (1853: 23) subsp. scopulorum ( Ginzberger 1921: 238) Plazibat (2009: 416) , Brassica botteri Visiani (1850: 135) , and Muscari speciosum Marchesetti (1882: 267) . In the island of Velika Palagruža, as well as in the nearby Mala Palagruža, some other very rare endemic taxa occur, like Limonium pelagosae Bogdanović & Brullo (2015: 23) , Minuartia verna ( Linnaeus 1767: 72) Hiern (1899: 320) subsp. insularis Trinajstić & Pavletić (1978: 6) , Centaurea ragusina Linnaeus (1753: 912) , Centaurea friderici Visiani (1847: 40) , and Cymbalaria visianii Kümmerle (1911: 299) , which are usually localized in rupestrian places.

Conservation status:— Loncomelos visianicum was recorded for a single location (Vela Palagruža), though currently considered ( Lansdown 2018) an extinct species (EX). Our recent surveys in the locus classicus led to the rediscovery of a single population, approximately represented by no more than 100 mature individuals growing in a very restricted area. The extent of occurrence (EOO) and the area of occupancy (AOO) are less than 1 km 2. Currently, the surface occupied by this geophyte is markedly affected by human activities (the presence of lighthouse keepers and tourist visitors) and seagulls, which caused a certain edaphic nitrification. According to the IUCN (2017) protocol, for its rarity, the low number of mature individuals and the restricted distribution, as well as for the environmental threats, L. visianicum should be included in the risk category Critically Endangered (CR, B1+B2ab,ii,iii).

Figures

FIGURE 1. Diagnostic features of Loncomelos visianicum. A. Flower, frontal view. B. Flower, lateral view. C. Outer tepal. D. Inner tepal. E. Bud. F. Outer stamen. G. Inner stamen. H. Pistil. I. Ovary, cross section. J. Stigma. K. Capsule. L. Bracts. M. Medium and small leaf, cross section. N. Large leaf, cross section. Drawings by Salvatore Brullo on leaving material collected by Bogdanović & Ljubičić s.n. (CAT).

FIGURE 2. Phenological features of Loncomelos visianicum A. Natural habitat in the type locality. B. Habit. C. Flower. D. Inflorescence (Photos by S. Bogdanović).

FIGURE 3. Chromosome complement (2n = 3x = 42 + 0−5B) of Loncomelos visianicum from type locality. A. Mitotic metaphase plate, arrows indicate accessory chromosomes. B. Idiogram.