Limonium korakonisicum R.Artelari & Valli, 2015

Valli, Anna-Thalassini & Artelari, Rea, 2015, Limonium korakonisicum (Plumbaginaceae), a new species from Zakynthos Island (Ionian Islands, Greece), Phytotaxa 217 (1), pp. 63-72 : 65-69

Limonium korakonisicum R.Artelari & Valli sp. nov.

Type :— GREECE, Ionian Island : Zakynthos, locality Korakonisi, 37°43’08’’N, 20°43’48’’E, on calcareous maritime cliffs and rocks, 10 m a.s.l., 14 September 2014, leg. A.- Th. Valli no 1200 (holotype UPA!; isotype B!) ( Figs. 3−4)

Diagnosis:— Planta perennis , glabra, griseo-viridis, 9–25 cm alta, foliis rosulatis, densis, pulviniformis, 3.0–29.0 × (0.15–)0.3–0.6(–0.7) mm, oblanceolatis-spathulatis, obtusis, rugosis ad verrucosis, mucronulatis, 1-nerviis, caulibus paucis, valde fragilis, plerumque non ramosis, scabridis, interdum proliferis, ramis sterilibus absentibus vel solo 1–3 per caulem, spicis (1–)2–6.5(–7.0) cm longis, spiculis 7–9 mm longis, (1–)2–5(–6)-floris, ad 2–4(–5) in 1 centimetro dispositis, bractea inferiore 2.0–2.9 × 1.2–2.0 mm, triangulari-ovata, apice acuta, bractea media 2.7–3.4 × 1.0–2.0 mm, bractea superiore 6.0–7.5 × 3.0–4.0 mm, obovato-elliptica, apice obtusa, margine late membranaceo, calyce (5.0–)6.0–7.0 mm longo, ex bractea superiore 1.5–2.0 mm exserto, tubo glabro vel sparsim piloso, lobis calycis 0.6– 0.7 mm, acutis.

Description:— Perennial plant, 9–25 cm tall, glabrous, with very few and very fragile grey-green stems. Leaves 3–29 × (0.15–) 0.3–0.6 (–0.7) mm on numerous small rosettes gathered to a very dense cushion-like formation up to 50 cm in diameter, uppermost leaves green at anthesis, lowermost ones brown and persistent after withering, oblanceolatespathulate, fleshy, grey-green, flat or sometimes v-shaped in cross-section, rugose to verrucate, obtuse, without revolute margins, mucronulate with a mucro ca. 0.1 mm long sometimes curved backwards, with one central nerve, gradually tapering into a petiole shorter than lamina. Stems erect, scabrid, usually unbranched, when branched the branches begin almost from the base and form an acute angle; the branches sometimes proliferous (with small leaf rosettes); sterile branches absent or only 1–3 per stem. Inflorescence corymbose, with very fragile segments. Spikes (1.0–)2.0– 6.5(–7.0) cm long, erect or slightly curved. Spikelets 7–9 mm long, composed of (1–)2–5(–6) flowers, 2–4(–5) per cm. Outer bract 2.0–2.9 × 1.2–2.0 mm, glabrous, triangular-ovate, acute, with a broad membranous margin, central part fleshy, brown, forming a point 0.4–0.5 mm. Middle bract 2.7–3.4 × 1.0–2.0 mm, glabrous, elliptical, hyalinemembranous. Inner bract 6.0–7.5 × 3.0–4.0 mm, glabrous, obovate-elliptic, obtuse, with a narrow membranous margin 0.4–0.5 mm wide; central part fleshy, forming a point 0.9–1.1 mm. Calyx (5.0–)6.0–7.0 mm long, exceeding the inner bract 1.5–2.0 mm; calyx tube glabrous or sometimes sparsely hairy; calyx lobes 0.6–0.7 mm, acute. Corolla pale lilac to white.

Etymology:— The specific epithet refers to Korakonisi, the type locality at the southwestern coast of the island of Zakynthos ( Fig. 2 ).

Ecology and distribution:— Limonium korakonisicum is currently known only from the type locality in Korakonisi area (South-Western Zakynthos Island). Korakonisi is an isolated rock connected to the main island by a narrow land-bridge and it is characterized by impressive geological formations ( Fig. 5A ). The species forms a small population, which includes 100 individuals (complete census), while the 67 of them are mature ( Fig. 6) according to IUCN definition ( IUCN Standards and Petitions Subcommittee 2014). Flowering from August to October, fruiting from September to November. L. korakonisicum seems to be extremely restricted, a common feature among several agamospermus taxa, especially in the genus Limonium ( Brullo & Pavone 1981, Artelari & Georgiou 1999). However, its occurrence in the neighbouring inaccessible rocks must not be excluded.

Limonium korakonisicum ( Fig. 5B, D, E & F ) grows in crevices of high, calcareous, sunny maritime cliffs and rocks with terra rossa, at an altitude of about 10 m a.s.l., together with another endemic Limonium phitosianum . L. phitosianum forms a larger population in the area of Korakonisi which includes 245 individuals, 183 (74.7%) of them are mature. The two local endemic Limonium taxa not only coexist but sometimes are intermingled, producing an amazing sight ( Fig. 5C ).

Other cohabiting taxa in the area are Crithmum maritimum L., Hypericum aegypticum L. subsp. webbii (Spach) N. Robson and Sarcocornia fruticosa (L.) A. J. Scott.

Conservation status: —According to IUCN (2014), Limonium korakonisicum fulfils Criterion D, mainly due to its very limited expansion/ restricted distribution (Extent of Occurrence less than 100 km 2 and Area of Occupancy less than 10 km 2), as well as its low number of mature individuals (less than 250). Thus, is here assessed as Endangered (EN). Moreover, in case of further touristic development in the area in the future, the species may be classified as Critically Endangered (CR). All the above reasons necessitate the long term monitoring of L. korakonisicum . Long term monitoring is essential so that required management measures can be taken to ensure the survivability of the species.

Taxonomic relationships:— Limonium korakonisicum belongs to the subgenus Limonium (sensu Lledó et al. 2005). It is well differentiated from the group of the sexual diploid Ionian endemics with 2n=18, which dominate in the Ionian Islands and the western coasts of the Greek mainland ( Fig. 1 ), as well as from all the other Limonium taxa which are known so far from the same area. On the contrary, it is related to the polyploid apomictic Limonium species occurring in the Aegean area and the eastern coasts of the Greek mainland ( Fig. 1 ). Among them, L. korakonisicum is more closely related to the recently described Cytherian endemic L. spreitzenhoferi Erben & Brullo (Brullo & Erben in press). L. spreitzenhoferi has as type a specimen of G.C. Spreitzenhofer (Iter Jonicum IV num. 18: Cerigo, auf den Felsen bei den Häusern im Hafen von Kapsali, 15 June 1880, holotype B photo! no. 10-0294995), which as it seems from the label, was originally identified as Statice sieberi Boiss. Based on this, material which we have collected from the same locality of Kithira Island treated in a previous paper as L. sieberi Kunze ( Artelari & Georgiou 2003: 495) is considered now as L. spreitzenhoferi . From the morphological point of view L. korakonisicum ( Fig. 5B, D, E & F ) clearly differs from L. spreitzenhoferi in having leaves on numerous small rosettes gathered to a very dense cushion-like formation up to 50 cm in diameter, fewer and very fragile stems all of them reaching at about the same height, denser spikes, shorter spikelets with more flowers per spikelet, as well as shorter outer bracts and calyces.

The coexisting species in the area, L. phitosianum , also has small leaf rosettes gathered to dense cushion-like formations which are much smaller (not more than 20 cm) than those of L. korakonisicum . The two taxa are readily distinguished ( Fig. 5C ) as L. korakonisicum has grey-green stems, grey-green leaves without revolute margins and with petiole shorter than lamina, segments of the inflorescence not articulate, fewer sterile branches, longer spikes and spikelets, longer outer and middle bracts, longer and obtuse inner bracts, and shorter calyx lobes. Furthermore, L. korakonisicum is found to be an apomictic polyploid species with 2n=6x=51 (see cytology and breeding system below), while L. phitosianum is a sexual diploid with 2n=2x=18. The main morphological diagnostic characters of L. korakonisicum , L. spreitzenhoferi and L. phitosianum are given in Table 1.

Chromosome number:— 2n=6x=51

Cytology and breeding system:— Limonium korakonisicum was found to be hexaploid with 2n=6x=51. The karyotype ( Fig. 7 ) possesses three long metacentric ‘marker’ chromosomes which, according to Erben (1978, 1979) are characteristic for the karyotypes of the taxa of the subgenus Limonium with the basic number x=8 and are missing in the taxa with x=9. Their occurrence indicates that the above chromosome number derived from the combination of 3 x 8 + 3 x 9 genomes ( Erben 1978, 1979), therefore it can be assumed that L. korakonisicum has a hybrid origin.

The study of breeding system of L. korakonisicum was carried out on all 67 mature individuals of the known population of the species. The analysis of pollen and stigma combinations revealed that the population of this taxon is monomorphic. All studied plants have the self-incompatible ‘A’ combination, i.e. ‘A’pollen and ‘Cob’ stigma ( Baker 1948, 1953, Erben 1978, 1979) indicating self-sterility. Pollen stainability values are very low (0 – 2%) and pollen grains are irregular in size. Stainable pollen grains are well-shaped and much larger than the unstainable ones, which are small and misshaped. Such pollen and stigma features characterize apomictic species ( Baker 1953). Although pollen stainability values are very low, relative reproductive success (RRS) of the species is high enough (75.6%). RRS is defined as the percentage of all ovules maturing into seeds ( Wiens 1984). The above data together with the hexaploid chromosome number support that L. korakonisicum is an apomictic species.

It is important to note here the discovery, for the first time in the Ionian area, of an apomictic polyploid taxon with a chromosome number derived from the combination of x=8 and x=9. According to our data so far such taxa are found in the Aegean area. A distribution map of the group of sexual diploid Ionian endemic species with 2n=18 and of apomictic polyploid species with 2n=34, 42, 43, 51 and 52 is presented in Fig. 1 . This map is based on known data ( Papatsou & Phitos 1975, Artelari 1984b, 1989a –c, 1992, Artelari & Kamari 1986, 1995, 2000, Artelari & Georgiou 1999, 2000, 2003, Georgakopoulou & al. 2006) as well as on other available data (Artelari & Georgiou unpublished).

Figures

FIGURE 1. Distribution map of sexual diploid Ionian endemic species with 2n=18 (●) and of apomictic polyploid species with 2n=34, 42, 43, 51 and 52 (©) in Greece. Symbols represent populations in which the chromosome numbers have been counted.

FIGURE 2. Map of Zakynthos Island where the only known population of Limonium korakonisicum R.Artelari & Valli is shown (red spot).

FIGURE 5. Habitat and morphological features of Limonium korakonisicum. A. Locality Korakonisi. B. A typical individual. C. The two local endemic taxa L. korakonisicum (left) and L. phitosianum (right) intermingled. D. Spikes, spikelets and flower of L. korakonisicum. E. A detail of the flower. F. Grey-green leaves.

FIGURE 7. Mitotic metaphase plate of Limonium korakonisicum with 2n=6x=51. Scale bar = 10 μm.