A new species of Silene sect . Dipterosperma ( Caryophyllaceae ) from Sicily

Brullo, C., Brullo, S., Giusso del Galdo, G., Ilardi, V. & Sciandrello, S. 2012. A new species of Silene sect. Dipterosperma (Caryophyllaceae) from Sicily. Anales Jard. Bot. Madrid 69(2): 209-216. Silene kemoniana, a new species of the section Dipterosperma from NW Sicily, is described and illustrated. It is a therophyte that occurs in mountains near Palermo, where it grows on Mesozoic limestones in xerophilous garigues. Its relationships with S. colorata and allied species are also examined. A key of the species belonging to sect. Dipterosperma is provided.


INTRODUCTION
Silene L. is the largest genus of the Caryophyllaceae with about 700 species distributed throughout the northern hemisphere, mostly in Europe, Asia and North Africa (Greuter, 1995).A rather critical group within this genus is represented by the annual populations usually grouped under Silene colorata Poiret s.l., that are widely distributed across the Mediterranean and Irano-Turanian regions.Previous authors (Maire, 1963;Pignatti, 1982;Talavera, 1990;Chater & al., 1993;Valsecchi, 1995;Greuter, 1997) have considered S. colorata to be a very variable species, encompassing differences in leaf shape, calyx indumentum, petals, capsule, carpophore and seeds.It is included in the sect.Dipterosperma (Rohrb.)Chowdhuri, which groups taxa with the following characters: annual and eglandular herbs, with hermaphrodite, erect flowers, arranged in monochasia or dichasia, the calyx hairy, not inflated, with 10 nerves, anthophore pubescent, petals with the limb deeply bifid and claw not or slightly auriculate, coronal scales present, seeds orbicular-reniform, with flat surfaces that are dorsally furrowed between 2 undulate wings.To treat this variability, several taxa at specific or infraspecific levels have been described within this critical group, and some of these still require further study.
During field work carried out in northern Sicily, an odd population of plants closely related to the Silene colorata group was encountered.After a revision of the taxonomic literature and herbarium specimens, it became evident that these plants were quite different from the hitherto known taxa of this group.The most marked diagnostic characters include its small habit, the stem that is branched only at the base and is prostrate-ascending, the few-flowered inflorescence, and petals with very narrow lobes.We believe that such morphological features deserve the recognition of the Sicilian plant as a new species, namely Silene kemoniana.The specific epithet refers to Kemonia, a small river that originates in the mountains near Palermo.

MATERIAL AND METHODS
Morphometric analyses were carried out on living plants at the original population site.For the taxonomic comparison with Silene colorata and allied species, herbarium material at CAT, and in some cases, living plants cultivated in the Botanical Garden of Catania, were used.

Seed morphology.
According to studies by Esau (1977), Barthlott (1984) and Gontcharova & al. (2009), the seed coat morphology is a constant character in many groups of plants, and it can permit good differentiation between species, and so is an important diagnostic taxonomic feature.Furthermore, the testa micromorphology can be a character that is so unequivocal that it may also have a phylogenetic value, as indicated by some recent studies (Johnson & al., 2004;Attar & al., 2007;Moazzeni & al., 2007).
In the genus Silene, several authors have investigated the seed morphology of many species, and have emphasized the remarkable interspecific variability in shape, size and microsculptures (Berggren, 1981;El-Oqlah & Karim,1990;Hosny & Zareh, 1993;Villa, 1995;Yildiz & Cirpici, 1998;Hong & al., 1999;Zareh, 2005;Yildiz, 2006;Yildiz & Minareci, 2008;Perveen, 2009;Fawzi & al., 2010;Ocaña & al., 2011).In order to compare S. kemoniana and S. colorata, the micro-morphology of their seed testa was also investigated (Fig. 3).Our results show that seeds of both species are orbicular-reniform, flat-concave laterally, alate and deeply canaliculate dorsally, with wings more or less undulate.From the micro-morphological viewpoint, the seed-coat of both species is characterized by very elongated and granulate epidermal cells that are short near the hilum and longer towards the periphery, with a colliculate outer periclinal wall provided with showy tubercles that are arranged in rows, and a more or less undulate anticlinal wall.However, several important differences, mostly concerning the primary and secondary sculptures of seed coat, can be observed when comparing S. kemoniana and S. colorata.In particular, S. kemoniana (Fig. 3A) has epidermal cells 65-140 × 13-19 µm, an outer periclinal wall that is roughly and loosely granulate, and anticlinal wall boundaries that are irregularly incise-undulate, canaliculate, with lacerate sutures, while S. colorata (Fig. 3B) has cells 65-110 × 22-30 µm, an outer periclinal wall that is minutely and densely granulate, and anticlinal wall boundaries that are more regularly undulate, flattened, with entire sutures.Other notable A new species of Silene sect.Dipterosperma differences can be observed at the bottom of the dorsal furrow, since S. kemoniana is characterized by several irregularly arranged papillae, interspersed with numerous minute wrinkles, whereas S. colorata has papillae that are regularly arranged in two rows mixed to minute dots.
Besides these morphological differences, these species are also ecologically distinct: since S. colorata is a psammophyte, growing on sandy soils of coastal and inland sands, whilst S. kemoniana is found in submontane garigues occurring on carbonatic substrates.In its small size and prostrate-ascending stems that are only basally branched, S. kemoniana is similar to S. nummica described by Valsecchi (1995) from the Central Mediterranean area.However, the latter is easily distinguished from the new species in having leaves that are thickened and with dense long hairs, solitary flowers, the calyx tomentose-hirsute, corolla lobes 4-5 mm wide, the capsule 5-6 mm, with teeth at maturity not reflexed, and seeds 1 mm in diameter, with wings that are flat and very short.Besides, the habitat of S. nummica is also different, since it is a species found in sandy or rocky coastal habitats.