A new species of Astragalus L . sect . Sesamei DC . ( Leguminosae ) from the southeast of Spain : Astragalus castroviejoi by

Talavera Lozano, S., Sánchez-Gómez, P., López García, D., Jiménez Martínez, J.F. & Mota Poveda, J.F. 2010. A new species of Astragalus sect. Sesamei DC. (Leguminosae) from the southeast of Spain: Astragalus castroviejoi. Anales Jard. Bot. Madrid 67(1):


Introduction
Astragalus is the most diverse genus of all Angiosperms, with more than 2,500 species.The genus is mainly distributed through arid and temperate regions of the Northern Hemisphere and South America.It is especially abundant in SW and SC Asia, where 1500 species are found, western North America (around 500 species) and in South America, especially in the Andean region (150 species) (Sanderson & Wojciechowski, 2000).Europe is host to 120 species (Podlech, 2008), although N Africa is also a centre of considerable diversity.Molecular studies (Sanderson & Wojciechowski, 2000;Wojciechowski & al., 1999) have indicated that the species from North and South America, the so-called "Neo-Astragalus", show little genetic diversity and are closely related to the annual species A. echinatus Murray, the only species of the sect.Pentaglottis Bunge endemic to the Mediterranean Region.Most species are perennial herbs or spiny bushes, but c. 70 species are strictly annual, all of them living in the Irano-Turanian and Mediter-ranean Regions.All annual species of Astragalus belong to the subgenus Trimeniaeus Bunge and can be divided into 13 sections, six of which are monospecific (Podlech, 1994), with sect.Sesamei DC. being the most diverse with 22 recognised species (Gazer, 1993).
In the marl-gypsum pastures of SE Spain, populations of taxon evidently belonging to Astragalus sect.Sesamei that are very similar in morphology to A. stella, but with fruits more like those of A. sesameus, have been found.All the members of sect.Sesamei are characterised by having mostly white basifixed hairs; stipules adnate to the petiole; dense inflorescences, that are axillary, and sessile or long-pedunculate; tubular calyx, with lanceolate teeth usually slightly shorter than the tube, rarely longer; flowers with the standard longer than the wings and keel; androecium diadelphous, 10 stamens, the vexillar stamen free; ovary pilose, with a longitudinal septum, bilocular, with (3)4-8 ovules per locule; style short, fat, curved, glabrous, ending in a semispherical humid stigma with no surrounding hairs; legume sessile, with a keel on the ventral face, and a groove in the dorsal one, ± pilose, bilocular, with (2)3 or more seeds per locule; seeds tetragonous, with a sunken hilum, ± flat, with smooth or rugulose surface, brownish-gray or greenish.Most species of this section live in SW Asia, although seven species are found in Algeria and six in Morocco (Gazer, 1993).Currently only three species of sect.Sesamei occur in Spain: A. scorpioides Willd., A. sesameus L. and A. stella L. (Podlech, 1999).
In this study we focused on a morphology and karyology of these populations that live in the marl-gypsum pastures of SE Spain so as to compare them with A. sesameus and A. stella, the two species with similar morphology in Astragalus sect.Sesamei (the A. stella group hereafter).

Materials and methods
The material used for karyological studies came from plants cultivated in the greenhouses at the University of Seville, originally from a population from Murcia in the marl-gypsum pasture of the A. stella group.
Chromosomes were observed in root tip meristematic cells that were pre-treated with 0.002 M 8-hydroxiquinolein for three hours at 4 ºC and subsequently fixed in Carnoy solution (3 : 1, 96% ethanol: glacial acetic acid) for at least 24 hours.Chromosomes were stained with hydrochloric acid-carmine according to Snow (1963).Images were taken with a Leica DC 300 inserted in an Axiophot Zeiss with Plan-Apochromatic 63/1.4 objective at 2.5 magnification.
For the terminology referring to chromosomes, we have followed Levan & al. (1964) and for size, Stebbins (1938).
Both vegetative and reproductive characters were quantified, based on the material of the A. stella group only, at the herbaria of the universities of Seville (SEV) and Murcia (MUB) (see Appendix 1).

Results and discussion
Astragalus stella group species have similar floral characters, with the standard oblanceolate, emarginate or retuse apex, and undifferentiated claw; wings with narrow-elliptic limb, obliquely bilobate, auriculate at the base, and a narrow claw nearly as long as the limb; keel smaller than both standard and wings, with nonauriculate, galeated limb and a broad claw, as long as or even longer than limb.All the flowers of these species encountered at anthesis had the anthers open at the end of the keel, and closely associated with the stigma, giving the impression that they had not been visited by bees.This leads us to think that the whole group is self-fertilising, as is the case with other annual species of Astragalus of the sections Bucerates DC. and Epiglottis Bunge (Gallardo & al., 1994).
Although petal morphology and disposition of the androecium and gynoecium are similar in the A. stella group, nevertheless, a series of characters serve to distinguish three taxa: the pedunculate or subsessile inflorescence, specially the morphology of the calyx, the number of ovules/locule in the ovary, the disposition of the legumes in the infrutescence, the dorsal and dorso-ventral width of the legumes, and also the length of the hairs on the legumes.These three taxa comprise A. stella and A. sesameus, and a new species to which we give the name A. castroviejoi, in honour and memory of the distinguished taxonomist Dr. Santiago Castroviejo Bolibar.
Following the description, we provide a key to identify these three species.
Phenology.April-May.Karyology.Chromosome number in Astragalus castroviejoi is 2n = 16 (Fig. 2A), as in A. sesameus and A. stella (Pretel Martínez, 1974).Chromosomes are small (1.6-1.79 µm; pairs VI to VIII of the karyotype) and medium-small (2.15-3.28µm; pairs I to V of the karyotype).Three pairs of chromosomes present centromere in median region (m; pairs IV, VI and VIII of the karyotype; Fig. 2B), three in the submedian region (sm; pairs II, III and V of the karyotype) and two in subterminal region (st; pair I and VII of the karyotype).The karyotype asymetry, sensu Stebbins (1971), is 3B.
Conservation.Only six small subpopulations are known, and these form a single population which is included in two 1×1 km 2 UTM squares.In 2009, two subpopulations are located in the province of Murcia, with 512 reproductive individuals, while the other four subpopulations are located in the province of Almeria, with 1186 reproductive individuals.The known area of distribution is about 15 ha in a total area of around 60 ha.
The natural habitat of Astragalus castroviejoi is open to many threats, mostly anthropic in origin, mainly related with agriculture and animal husbandry.
A good part of the potential habitat of the species is at present occupied by extensive cereal crops, and recent ploughing, for example, has seriously affected one of the subpopulations found in Murcia.Given the absence of any steep slopes in the area where A. castroviejoi is found and the proximity to cultivated zones, there is a strong risk that the remaining enclaves will suffer a similar fate.As regards grazing, the Murcian subpopulations in particular are exposed to strong pressure, and A. castroviejoi plants have not only been eaten, but are also exposed to the harmful effect of substrate compaction.Given the annual character of the species and the irregular nature of rainfall in the area, extreme inter-annual fluctuations in plant numbers are to be expected, although this remains to be confirmed.According to the data available, and applying IUCN (2001) criteria, A. castroviejoi should be considered as a threatened species within the category CR B1ab(i,ii,iii,iv,v) + 2ab (i,ii,iii,iv,v), and it is highly probable that sub-criterion "c" could be applied once the populations have been monitored several years.In accordance with the above, we recommend the inclusion of A. castroviejoi in Red lists and Catalogues of legally protected species at regional, national and European levels, a measure that should help the short-term stabilisation and recovery of known populations.