Sisymbrium isatidifolium Blanca, Cueto & J. Fuentes, 2015

Blanca, Gabriel, Cueto, Miguel & Fuentes, Julián, 2015, Sisymbrium isatidifolium (Brassicaceae): a new species from southern Spain, and the identity of S. hispanicum Jacq., Phytotaxa 220 (1), pp. 43-53 : 44-47

Sisymbrium isatidifolium Blanca, Cueto & J. Fuentes , sp. nov. ( Figs. 1 & 2 )

Species related to Sisymbrium hispanicum . It differs by its lowermost leaves oblong-obovate, obtuse, dentate to subentire, the middle ones oblong-obovate to oblong-linear, smaller flowers [sepals 2.4– 3 mm, petals (3.5–) 4–5 mm] and fruits generally smaller [(10–)15– 25(–30) × 0.6–0.7 mm].

Type: — SPAIN. Granada: Orce, Llano de Almaida, margas yesíferas, 970 m, 30 Mayo 2013, G. Blanca, M. Cueto & J. Fuentes 61401 (holotype GDA!, isotype HUAL!).

Annual to biennial herb, unicaule, glabrous, and glaucous. Stem (15–) 20–70 cm, erect, simple, branched in the upper half, often with reddish tones. Leaves alternate, the lowermost 3–25 × 1–4 cm, rosulate, oblong-obovate, obtuse, dentate to subentire, narrowing progressively towards the base, sometimes with reddish tones in the central nerve and throughout the underside of the blade; the middle ones oblong-obovate to oblong-linear, sessile or subsessile, not amplexicaul at the base, serrate or entire, gradually decreasing in size upwards. Synflorescence ramose, corymbiform, with branches sometimes subpatent; racemes of up to 50–60 flowers, ebracteate. Pedicels (3.5–) 4–6 mm, straight at flowering and sharply incurved in the fruit, 0.5–0.6 mm thick in the middle and thickening at the apex (to 0.8 mm). Sepals 2.4– 3 mm, erect and very open, incurved at the base, oblong, yellow; the lateral ones slightly gibbose at the base. Petals (3.5–) 4–5 mm, with obovate blade and attenuated to a claw. Androecium tetradynamous; lateral stamens (2–)2.5– 3 mm, the middle ones (3–)3.5– 4 mm; anthers 0.7–0.9(–1) mm. Siliques (10–)15–25(–30) × 0.6–0.7 mm, densely arranged, linear, slightly torulose, somewhat compressed, and with three veins well marked at maturity; style 1–1.8 mm, initially thicker and at maturity of the same width as the valves; stigma strongly 2-lobed; seeds 10–20, measuring 0.9–1 × 0.5–0.6 mm, uniseried, with incumbent cotyledons.

Etymology: —The specific epithet refers to the similarity of the leaves to those of Isatis tinctoria Linnaeus (1753: 670) .

Distribution and habitat: — Sisymbrium isatidifolium is endemic to southern peninsular Spain, restricted to the provinces of Albacete, Jaén, Granada, and Almería ( Fig. 3 ).

Grows on marly and gypsiferous soils, forming part of the open esparto grasslands or weedy and ruderal communities in the mesomediterranean bioclimatic belt at elevations between 550–1500 m. a.s.l. and in a dry ombrotype climate.

Phenology: — Sisymbrium isatidifolium flowers from May to June, and produces fruits from June to July.

Additional specimens examined (paratypes): — SPAIN. Albacete: Balazote y Venta del Conejo , 7–800 m, 17 June 1891, Porta & Rigo 45437 ( MA!) ; El Salobrar, cerca de Albacete, 740 m, 30SWJ90, 12 June 1986, J. Molero 428015 ( MA!) ; entre Urbanización Casas Viejas y autovía de Jaén, 686 m, 30SWJ917147, 23 May 2012, A. Valdés Franzi 59889 ( GDA!) ; La Felipa, 680 m, 30SXJ0318, 10 May 1986, J. M. Herranz 355668 ( MA!) ; La Pulgosa, 690 m, 30SWJ9813, 29 May 1986, J. M. Herranz 355667 ( MA!) ; N301 , km 264, entre Albacete y Chinchilla de Monte Aragón, 710 m, 25 June 1996, A. Schinini et al. 632048 ( MA!). Almería: María , carretera AL –9102, sobre el Barranco del Saltador, 1095 m, 30 May 2013, M. Cueto, G. Blanca & J. Fuentes 25586 ( HUAL!) ; María, prox. Cortijo del Ventorrillo , 1015 m, 30 May 2013, M. Cueto, G. Blanca & J. Fuentes 25587 ( HUAL!) ; Oeste de María, 9 June 1976, C. Gómez Campo 619991 ( MA!). Granada: Entre Puebla de Don Fadrique y Cañadas de Cañepla , 20 June 1989, G. Blanca & M. Cueto 29584 ( GDAC!) ; Orce , cañada de Don Tomás, 1000 m, 30 May 2013, M. Cueto, G. Blanca & J. Fuentes 25588 ( HUAL!) ; Orce, Fuente Nueva, entre Cortijo Varela y Cortijo del Ñoño o de la Mojonera, 975 m, 30SWG4976, 23 May 2013, G. Blanca, M. Cueto & J. Fuentes 61402 ( GDA!). Jaén: Barranco del río Segura , 1500 m, June 1906, E. Reverchon 45469 ( MA!) ; Le Pozo, 1500 m, May 1905, E. Reverchon 45470 ( MA!) ; Le Pozo, 1500 m, June 1905, E. Reverchon 45466 & 45467 ( MA!) ; Sierra de Cazorla , 1500 m, June 1901, E. Reverchon 45468 ( MA!) .

Comparison and discussion: —The identity of Sisymbrium hispanicum is controversial. In the original description of this species, Jacquin (1784: 12) indicated that it had “…. foliis lanceolatis, serratis, sessilibus ”, as can be clearly appreciated in the detailed plate of the species (Tab. 124). This same characteristic also appears in the complete description of the species that this same author included in the what must have been an earlier work, but which appeared two years later ( Jacquin, 1786: 69): “ …caulem…erectum & ex omnium fere foliorum axillis ramosum. Haec sunt lanceolata, acutiuscula, rariter serrata, sessilia & glaucescentia ”. These same characteristics were mentioned by later authors such as Willdenow (1801: 507), De Candolle (1821b: 463) and even Willkomm (1880: 799). Nevertheless, this latter author, pointing out the distribution of this species, included the exsiccata collected by Bourgeau in southern Spain (between Albacete and Chinchilla, Albacete Province, and near María, Almería Province), which correspond to a completely different plant (which we propose as Sisymbrium isatidifolium , sp. nov.), characterized by its lowermost leaves oblong-obovate, obtuse, dentate to subentire, the middle ones oblong-obovate to oblong-linear. Since Jacquin (1786) had not indicated a precise location for his species (only the specific epithet make reference to Spain), the details from Willkomm (l.c.) prompted a change in the conception of S. hispanicum , which has been assumed by later authors ( Schulz 1924, Guinea 1970, Pujadas Salvá 1993, among others).

Although, as stated above, a colour plate illustrates the identity of S. hispanicum (Jacquin 1784: tab. 124), where further details can be seen, we undertook a search for the specimens used at the time by Jacquin. As D’Arcy (1970) commented, there is no single “Jacquin Herbarium”, but rather the material is scattered throughout several European herbaria. Specifically in the Hamburg Herbarium (HBG), the specimen numbered 506246! was chosen as the typus by O.E. Schulz (in sched.), from the herbarium of Willdenow. In this specimen, the leaves are lanceolate and the siliques are up to 27 mm (still immature) with strongly incurvate pedicels.

Other characters that have been used to differentiate a S. hispanicum from other closely related species are the undivided leaves and the lack of indument, especially at the base of the stem. These two characteristics are of only limited use, as some specimens exist in the most closely related species with at least the middle leaves undivided and linear lanceolate ( Table 1). Regarding the indument, in the same species and in the same population, specimens can be completely glabrous together with others having hirsute stems, especially towards the base; this character has been used especially to distinguish S. contortum , which we consider synonymous of S. hispanicum after a detailed study of the data on the protologue and the typus deposited in the Herbarium del Jardín Botánico de Madrid (MA 476339!).

Table 1 lists the main differences between Sisymbrium isatidifolium and the other more closely related species. It is distinguished from the others by the type of basal and middle leaves. Also, S. chrysanthum is distinguishable by its very short siliques and, especially, for being wider, more or less appressed and parallel to the axis, with similarly appressed pedicels, much thinner than the silique; S. hispanicum has larger flowers and fruits; S. crassifolium bears much larger flowers and fruits, while S. assoanum has lax racemes, the fruits do not overlap, and the fruiting pedicels are generally longer, straight, and far thinner than the silique.

Figures

FIGURE 1. A–D Sisymbrium isatidifolium (from the holotype). A, Lower part; B, middle leaves; C, detail of the synflorescence; D, flower; E, silique.

FIGURE 2. A–D Photographs of Sisymbrium isatidifolium: A, Habit; B, detail of the basal leaves; C, detail of the raceme; D, siliques.

FIGURE 3. Map of the known populations of Sisymbrium isatidifolium.