Helictotrichon devesae, a new endemic grass species from Castilla-La Mancha (Central Spain)

Romero Zarco, C. 2007. Helictotrichon devesae, a new endemic grass species from Castilla-La Mancha (central Spain). Anales Jard. Bot. Madrid 64(2): 205-211. Helictotrichon devesae Romero Zarco (Aveneae; Poaceae), a new grass species is described and its anatomical and morphological characters are compared in relation to other species in the genus.

The Mediterranean region is the likely scenario for recent speciation events involving ancestors of the pre-Mediterranean flora, probably similar to now existing species in South-eastern Asia or tropical East Africa (Röser, 1996: 256).The genus' geographic range in Spain is conditioned by the orophilic or somewhat steppe character and mainly basiphilic affinity of its species.
Two isolated areas are known to include Helictotrichon species: one in the North and another in the South-East (Fig. 1).The former comprises a small portion of the Iberian System, Central and Western Pyre-nees and the Cantabrian Range, where the endemic H. cantabricum (Lag.)Gervais grows in a great variety of plant communities from sea level to 2200 m.The meso-xerophilic Alpine-Atlasic H. sedenense (DC.)J. Holub occurs in alpine meadows, subalpine and oromediterranean dwarf-shrub communities, and open subalpine coniferous woodlands (Röser, 1996).
In the second area, south-eastern Iberia, H. sedenense grows in open hemicryptophytic formations affected by cryoturbation (cryoromediterranean) and at lower altitudes in xerophilic spiny shrubs (oromediterranean), from 2000 to 3300 m above sea level.The H. filifolium (Lag.)Henrard complex occurs in most of SE Spain, from the Sierra de Grazalema (Cádiz province, S Spain) to Segorbe (Castellón province, E Spain), including Sierra de Cazorla and the Júcar valley.In this interesting complex, low ploidy levels (2x, 4x, 8x) are found in the central part of the Betic Ranges (S Spain: Sierra de Rute, Sierra Tejeda, south of Jaén province and several places in Granada province, specially in Sierra Nevada).In a previous paper Romero Zarco (1984) identified these populations as H. filifolium subsp.velutinum (Boiss.)Romero Zarco.However, Röser (1989Röser ( , 1996Röser ( , 2006)), considered these plants to be very well delimited from the rest of the complex and worth of specific recognition as H. sarracenorum (Gand.)J. Holub.Awaiting for future phylogenetic evidences, we accept Röser's proposal, mainly because it seems more consistent with the taxonomic treatment of the genus.It has been suggested that plants with 2n = 70 (10x) from the western Betic ranges (coexisting with Abies pinsapo Boiss.)correspond to H. filifolium subsp.arundanum Romero Zarco, a taxon accepted by Röser in his taxonomic (Röser, 1989) and ecogeographic (Röser, 1996)  In 1989, we found a herbarium specimen labelled "Helictotrichon filifolium" (MA 447900).The plant was collected in 1976 near Puebla de Almoradiel, in Toledo province, 70 Km away from the nearest localities known for that species.It was immediately evident that its small spikelets, extremely narrow leaves and pale basal sheaths did not match well with the characters of any known species of the genus Helictotrichon.The presence of hairs on some leaves, a typical character of young individuals of the Helictotrichon filifolium complex (Romero Zarco, 1984), led to the assumption that it was H. sarracenorum, but the locality of origin was out of the expected distribution range.Consequently, it was set aside as "study material" pending Dr. Röser's review of the genus in 1989.Nevertheless, his ample and excellent review did not

Material and methods
Herbarium material from the Universities of Seville (SEV) and Barcelona (formerly BCF, currently included in BCN) were used to illustrate leaf anatomy.Additional material from the Royal Botanic Garden of Madrid has been used to described the new species.Data previously published by the author have been included in this study (Romero Zarco, 1984, 1985a).Cross-sections of leaf blades were made by hand using well developed, basal leaves from innovations shoots.Pollen grains from unopened anthers where observed by optical microscopy in isotonic water solution.

Leaf anatomy
In general leaf blades of the new taxon show a Helictotrichon devesae, a new endemic grass species from Castilla-La Mancha structure similar to those from other xerophilic species in the genus.The new taxon presents shorter and narrower leaf blades than other close species, accompanied by an overall reduction in vascular tissue.It presents 7 vascular bundles, instead of the 9 to 13 which are common in the rest of the species, and the girders are absent or very reduced, a character yet unreported for this genus (Fig. 2).

Pollen grains
Pollen grains were observed and measured.The appearance was normal, and the size ranged from 29.7 to 33.8 µm.
Flowering time in July.Habitat: steppe-subsaline grassland community of Lygeum spartum, c. 700 m above sea level.
The name is dedicated to Dr. J.A. Devesa Alcaraz, author of interesting taxonomic studies on Spanish grasses and composites.The new species is known only from the type locality in Central Spain, where it has probably not been collected since 1976.

Discussion
Leaf blade anatomy in cross-section of the new species is very similar to those of other grasses adapted to xeric environments.Thus, the differences in leaf anatomy between the meso-xerophilic H. sedenense and the extreme xerophilic H. devesae are parallel to those observed in other grass genera, like the closely related Pseudarrhenatherum.The Eurosiberian Pseudarrhenatherum longifolium (Thore) Rouy presents wide, soft blades whereas P. pallens (Link) J. Holub, an endemic species from central-western Portugal limestone areas, resembles our new species in leaf anatomy (Romero Zarco, 1985b).The evolution from meso-xeromorphic to strictly xeromorphic species in Mediterranean perennial oats has also been documented by Röser (1989Röser ( , 1996Röser ( , 1998)).
Two other non-Spanish Helictotrichon species have similar leaf blade anatomy than that of H. devesae: H. setaceum (Vill.)Henrard, a West-Alpine species belonging to the H. parlatorei group, and H. desertorum (Lees.)Nevski, from the steppes and rocky hills of Eastern Europe and Western Asia (see Saint-Yves, 1931, sub Avenastrum).The former differs from our species mainly in its sinaptospermic spikelets, whereas the latter differs in its elongated ligules.
The spikelets of H. devesae show a similar morphology and structure to those of other Spanish species (Table 1): the rhachilla disarticulates below each floret, so the dispersal unit is a single mature floret.By contrast, in the Alps-endemic H. parlatorei group (Röser, 1989: 65), the spikelets disarticulate only above the glumes, and the dispersal units are sinaptospermic.This character (probably derived) occurs in other Avenea genera, e.g.Avena sterilis group, Pseudarrhenatherum and Holcus.
Regarding spikelet size, H. devesae resembles H. sedenense and small-spikelet individuals of H. sarracenorum (Table 1).It differs from both, however, in its smaller leaf-blade diameter and sclerenchyma pattern.The persisting leaf pubescence observed in young individuals of H. devesae leaves usually occurs in H. sarracenorum, but in the former the hairs are shorter (0.1-0.2 mm) and scattered.Setaceous leaves are present in both H. devesae and H. filifolium subsp.filifolium however, in H. filifolium var.filifolium from SE Spain (0,5-1 mm in diameter), well-defined sclerenchyma girders are visible in cross-section.Similar differences separate H. devease from H. cantabricum, though the angular shape of the ribs is common in both species.Differences in leaf anato-my have been shown to persist in cultivated plants of Helictotrichon taxa (Gervais, 1973;Röser, 1989).
The species most closely related to H. devesae is H. convolutum (C.Presl) Henrard, a diploid, xerophilic, central to eastern Mediterranean species proposed by Röser (1996: 237) as a geographical vicariant to the H. filifolium-sarracenorum complex.The cross-section leaf blade of H. devesae is very similar to those of H. cantabricum and H. convolutum (see Gervais, 1973, and Fig. 2), indicating a close affinity of the former taxon to the latter taxa, probably originated in the Eurosiberian part of the Mediterranean basin, whereas the H. filifolium-sarracenorum complex probably originated in the Betic-North African area.
It is highly unlikely that the new species could be a hybrid as the only possible extant parental species in the region is H. filifolium, and intergeneric hybrids do not occur between this species and other congeners or non-congeners (Gervais, 1983).Furthermore, the pollen grains show normal shape and their size falls within the known range of other  (López, 1976).
tocenoses (the plant communities included, among others, Schoenus nigricans, Plantago maritima, Doricnium gracile, Linum maritimum, Agrostis stolonifera and Cynodon dactylon).These data suggest that H. devesae could be a new and noteworthy example of grass speciation related to ecogeographic adaptations.
The original population (lecotype) of H. devesae, was destroyed by agricultural practices some years ago (Dr.Cirujano, in lit.).Though the plant was seen (but not collected) at other Schoenus nigricans sites in the La Mancha area.Further search on populations of H. devesae from Central Spain (River Guadiana Valley and the surrounding mountains) are needed to establish the ecology, distribution and ploidy level of this species.
studies.The more extended H. filifolium subsp.filifolium includes two varieties: var.cazorlense Romero Zarco (2n = 98) distributed in Sierra de Cazorla, Sierra del Pozo and perhaps in other central Betic mountains, and var.filifolium (2n = 84) somewhat smaller and with relatively narrower leaves, being the single Helictotrichon representative ocu-rring in Central Spain (Albacete and Ciudad Real provinces, and Serranía de Cuenca).