Odontites sillettii Brullo, Tomaselli & Wagens., 2015

Brullo, Salvatore, Tomaselli, Valeria & Wagensommer, Robert Philipp, 2015, A new species of Odontites (Orobanchaceae) from southern Italy, Phytotaxa 213 (3), pp. 271-281 : 273-279

Odontites sillettii Brullo, Tomaselli & Wagens. , sp. nov. Figs. 1–2 .

Species Odontite rigidifolio similis sed ramis plerumque ramosis, foliis subcylindricis vel leviter planis, inconspicui pedunculi praeditis, inflorescentia 1.5–3 cm longa, 5–12 floribus, bracteis 2–2.5 mm latis, calyce 4.5–5 mm longo, dentibus calycinis ovato-triangularibus, ventraliter densis longioribusque pilis, superioribus 1.8–2 × 1.4–1.5 mm, inferioribus 1.5 × 1 mm, rectis, tubo corollino 3–3.5 mm longo, labio superiore 4–4.2 mm longo, inferiore 2.8–3 mm longo, lobis 1.2–1.3 mm longis, laeviter retusis, filamentibus staminalibus superioribus 3 mm longis, inferioribus 2.5 mm longis, antheris 1.1–1.2 mm longis, rotundatis apice, 1–3 pilis ad basim techarum, stylo albido, stigmate capitato, 0.3 mm longo, capsula usque ad 3 mm lata, semine 1.3–1.5 mm longo.

Types: — ITALY. Apulia: Santeramo in Colle, loc. Costa Mandrino, on limestones, 40°48’55’’N, 16°46’55’’E, 430 m, 25 September 2013, G.N. Silletti s.n. (holotype CAT!, isotypes: CAT!, FI!).

Herb annual, 7–30 cm tall, erect, glaucescent, with appressed unicellular hairs, 0.1–0.2 mm long, mixed with short glandular hairs, covering the whole stem surface. Stem branched from the basis, with 6–13 internodes; branches divaricate-patent, adscendent in the terminal part, opposite, 2–10(16) cm, usually branched in the basal part. Leaves precociously deciduous, linear, entire, opposite, subcilindrical to slightly flat, 2–10 × 1 mm, inconspicuously pedicellate. Inflorescence subspicate, simplex, acropetal, with 5–12 flowers, 1.5–3 cm. Bracts ovate-lanceolate, entire, 3–5 × 2–2.5 mm, shorter than calyx. Calyx 4.5–5 mm, with tube 3 mm and teeth unequal, ovate-triangular, densely hairy in the adaxial face with hairs 0.25–0.3 mm; upper teeth 1.8–2 × 1.4–1.5 mm, lower teeth straight, 1.5 × 1 mm. Corolla totally purplish or yellowish below and purplish above, glabrous, 7–8 mm with tube 3–3.5 mm; upper lip 4–4.2 mm, longer than the lower one, which is 2.8–3 mm and divided in 3 subequal straight lobes, slightly retuse at apex, 1.2–1.3 mm, on the adaxial surface with 2 prominent glandular ridges. Stamens included in the upper lip, with filaments glabrous, upper ones 2.5 mm and lower ones 3 mm, anther pale yellow, 1.1–1.2 mm, apiculate at the basis, with spiral twisted hairs at the rounded apex and 1–3 straight hairs at the basis of each theca. Pistil with ovary elliptical, flat, densely hairy above, 1.2–1.6 mm; style whitish, curved at the apex, 5–5.6 mm; stigma greenish, capitate, minutely papillose,

0.3 mm. Capsule oblanceolate, 6–7 × 2.5–3 mm, hairy above, inside with some hairs along the midrib, 8–10 seeded.

Seed subelliptical, 1.3–1.5 mm.

Seed micro-morphology: ─ According to literature, the exomorphic features of seed testa, based on scanning electron microscopy (SEM), can be used as additional character for the identification of taxa at specific or subspecific level ( Barthlott 1981, Fitsch et al. 2006, Kasem et al. 2011). In particular as concerns the Scrophulariaceae s.l. (at that time, including Orobanchaceae partim), several studies on the seed testa of taxa belonging to various genera of this family were performed by various authors ( Musselman & Mann 1976, Elisen & Tomb 1983, Bolliger 1996, Juan et al.

1996, 2000, 2008, Martínez-Ortega & Rico 2001), who used them in resolving problems regarding the systematics of critical species or groups. In fact, seed sculptures are usually considered as a conservative and stable character, having relevant taxonomical and phylogenetic implications.

Previously, the seed testa sculptures of the species belonging to the genus Odontites s.l. was examined in detail by

Juan et al. (1996) and Bolliger (1996), who point out that although the seeds of the various species have an aspect quite similar, there are significant differences in their size, as well as on the shape and number of epidermal cells. Usually,

the seed coat is characterized by several longitudinal slightly raised ridges, contracted at the two ends. Between the ridges there is a row of narrow cells arranged transversely having a scalariform appearance. The entire cell surface is minutely wrinkled, with slightly depressed anticlinal walls and uniformly convex periclinal walls. The most significant difference between O. sillettii and O. rigidifolius is in the dimension of the cells, that, limitedly to those ones of the central part, in the first have a length of 50–60 μm and a width of 15–22 μm ( Fig. 3A 2-3 ), while in the second have a length of 70–80 μm and a width of 8–17 μm ( Fig. 3B 2-3 ). Besides, the two species differ also in the size of the seed, which in O. sillettii is 1.3–1.5 mm long ( Fig. 3A 1 ), while in O. rigidifolius is 1.4–2.2 mm long ( Fig. 3B 1 ).

Pollen morphology:— As emphasized by Bolliger & Wick (1990) and Bolliger (1996), the pollen grain in the species of Odontites are quite uniform as concerns the symmetry (radially symmetrical), polarity (isopolar), aperture type (tricolpate), exine sculpturing (irregularly micro-reticulate), furthermore in the equatorial view there are circular depressions in the mesocolpium, due to a ring-like wall thickening ( Halbritter & Hesse 2004). All these features are also present in the pollen grains of O. sillettii ( Fig. 4A ) and O. rigidifolius ( Fig. 4B ) observed by SEM in dry conditions. Besides, no relevant differences were detected by the comparison between the pollen of the two species.

Habitat and Distribution:— Odontites sillettii is a rare and localized therophyte collected in S Italy, where it was observed in some places near Santeramo in Colle in central Apulia ( Fig. 5 ). It occurs on a calcareous plateau, where it grows mainly in abandoned fields and sub-nitrophilous meadows at an elevation of 375– 450 m.

Etymology:— The specific epithet refers to Giuseppe N. Silletti, Regional Commandant of Apulia of the State Forestry Corps, who collected the species for the first time.

Phenology: —Flowering September to November, fruiting October to December.

Conservation status: —According to the field investigation, the new species has a very restricted almost punctiform distribution. In addition, the few known populations are usually represented by a limited number of individuals, which is annually quite variable being a therophyte. The growing sites of this plant are currently threatened by fire and grazing, which could lead to a significant decrease of the populations in the area. Therefore, according to the IUCN (2014) criteria, we propose to include this species in the following category: Endangered EN B1ab(i,ii,iii,iv,v)+2ab(i, ii,iii,iv,v).

Taxonomic remarks: —Morphologically, Odontites sillettii seems closely related to O. rigidifolius in having in common a trait combination quite significant from the taxonomical point of view. In particular, both species are annual, characterized by a typical candelabra shaped habit, linear leaves, calyx without glandular hairs, corolla glabrous in the abaxial side and entirely purplish or bicoloured (yellow below and purplish above), with occurrence of glandular ridges inside the lower lip, and stamen filament glabrous. In order to verify the morphological differences between these two species, living material from some Sicilian localities, herbarium specimens and literature data regarding O. rigidifolius were examined. This investigation allowed to put in evidence that the latter species shows remarkable diacritic features from O. sillettii ( Table 1). In fact, O. rigidifolius is characterized by hairs occurring only on two opposite faces of the stem, lateral branches usually not branched, up to 25 cm, leaves flat, canaliculate, sessile, broadened at the base, inflorescence 4–10 cm, (8)12–20 flowered, bracts 1.7–2 mm wide below, calyx 4.5–7(9) mm, with teeth triangular-lanceolate, covered by scattered and short hairs in the adaxial face, the upper ones 2–2.5 × 1–1.2 mm, the lower ones 1.7–2 × 0.9–1.1 mm, converging toward the apex, corolla with tube 3.8–4(4.5) mm, upper lip 4–5 mm, lower lip 2.4–2.6(3.5) mm, having lobes rounded, 0.8–1 mm, upper stamen filaments 2–2.5 mm and lower ones 3–3.5 mm, anthers 1.3–1.6 mm, obtuse at the apex, provided with 10–14 erect hairs for theca, style violet at the base, up to 6 mm and stigma cylindrical, 0.6 mm, capsule narrowly ellipsoid, 2.3–2.6 mm wide, 16–20 seeded, seed 1.4–2.1 mm ( Fig. 6 ).

Besides, the two species show different ecological requirement, since O. sillettii is localized on limestone, where it occurs in abandoned fields and seminatural grassland at about 375–450 m of elevation, while O. rigidifolius is linked to clayey or metamorphic substrata, where it is a member of more or less mesophilous meadows at 10–1500 m of elevation. According to literature data ( Bolliger 1996, Giardina et al. 2007) and herbarium investigation, O. rigidifolius shows a wide distribution in Sicily ( Fig. 5 ).

According to literature ( Webb & Camarasa 1972, Pignatti 1982, Bolliger 1996, Rico et al. 2008), the genus Odontites contains mainly annual species, while the perennial ones are few in number. Within the annual plants, there are species showing a hairy or glabrous corolla, among the latter the colour varies from entirely purplish to yellow, as well as can be yellow below and purplish above. Within this group there are species characterized by an entirely purplish corolla represented by O. purpureus ( Desfontaines 1798: 36) Don (1837: 611) , O. discolor Pomel (1874: 301) , Odontites lapiei Battandier (1910 : LXX), O. maroccanus Bolliger (1996: 135) and O. violaceus Pomel (1874: 301) , and other ones with yellow corolla, as O. citrinus Bolliger (1996: 157) , O. powellii Maire (1924: 389) , O. triboutii Grenier & Paillot (1864: 81) and O. vulcanicus Bolliger (1990: 116) . The only species showing usually a bicoloured corolla similarly to O. sillettii and O. rigidifolius is O. foliosus . However, the latter differs considerably from both species in the stem branching, shorter calyx, covered by glandular hairs, corolla lower lip without glandular ridges and the anther thecae almost glabrous.

All the species characterized by glabrous corolla, having an essentially Maghrebian distribution ( Morocco, Algeria and Tunisia), show on the whole clear relationships with O. sillettii and O. rigidifolius , that therefore can be both considered as species with a N-African origin. Clearly, they are differentiated from the allied Maghrebian species as a consequence of their geographical isolation, which is even more marked as concerns O. sillettii .

Paratypes: — ITALY. Apulia:Santeramo in Colle, loc. Collettore San Giuseppe, incolto, 40°44’00’’N, 16°42’40’’E, 375 m a.s.l., 06 October 2014, G.N. Silletti & V. Tomaselli s.n. (CAT!).

Examined material of O. rigidifolius : — ITALY. Sicily: Mazara del Vallo, Torretta Granitola , 27 September 1973, S. Brullo s.n. ( CAT!) ; Sicily: Troina , 05 July 1983, S. Brullo s.n. ( CAT!) ; Sicily: Lago Quattrocchi , 29 September 1985, G. Spampinato s.n. ( CAT!) ; Sicily: Ficuzza , 04 October 2014, S. Cambria & V. Ilardi s.n. ( CAT!) .

Figures

FIGURE 1. Diagnostic features of Odontites sillettii. A. Habit. B. Flower with bract (lateral view). C. Flower (ventral view). D. Corolla (entire). E. Corolla (open). F. Calyx (ventral view, open). G. Anther. H. Pistil. I. Stigma. J. Capsule. K. Seeds. L. Bracts. M. Stem with leaves. Illustration by Salvatore Brullo based on type material, Silletti s.n. (CAT).

FIGURE 2. Odontites sillettii. Inflorescence and flower details (Photos by G.N. Silletti).

FIGURE 3. SEM micrographs of seed coat of Odontites sillettii (A1–3) and O. rigidifolius (B1–3) at low magnification (A1 and B1 x 60), at medium magnification (A2 and B2 x 500) and at high magnification (A3 and B3 x 1500), from type material, Silletti s.n. (CAT) and from Ficuzza, Cambria & Ilardi s.n. (CAT).

FIGURE 4. SEM micrographs of pollen grains of Odontites sillettii (A 1-2) and O. rigidifolius (B 1-2) at lower magnification (A 1 and B 1 x 2500) and higher magnification (A 2 and B 2 x 9000), from type material, Silletti s.n. (CAT) and from Ficuzza, Cambria & Ilardi s.n. (CAT).

FIGURE 5. Geographical distribution of Odontites sillettii (star) and O. rigidifolius (dark dots from herbarium data and empty dots from literature).

FIGURE 6. Diagnostic features of Odontites rigidifolius. A. Habit. B. Flower with bract (lateral view). C. Flower (ventral view). D. Corolla (entire). E. Corolla (open). F.Calyx (ventral view, open). G. Anther. H. Pistil. I. Stigma. J. Capsule. K. Seed. L. Bracts. M. Stem with leaves. Illustration by Salvatore Brullo based on specimens from Ficuzza, Cambria & Ilardi s.n. (CAT).