Leucanthemum ligusticum Marchetti, Bernardello, Melai & Peruzzi, 2012

Melai, Martina, Marchetti, Dino, Bernardello, Remo & Peruzzi, Lorenzo, 2012, A new diploid species of Leucanthemum (Asteraceae, Anthemideae) from Liguria (northwestern Italy), Phytotaxa 66 (1), pp. 27-37 : 28-31

Leucanthemum ligusticum Marchetti, Bernardello, Melai & Peruzzi , sp. nov. ( Figs. 1 –2)

Type:— ITALY, Liguria. Val di Vara (La Spezia), Rocchetta di Vara , alla base del M. Nero, ca. 225 m, 7 May 2011, D. Marchetti s.n. (holotype: PI!; isotype: B!, FI!, GE!)

A L. plurifloro Pau flore ligulato 2.5–3.8(4.8) non (3.0)3.5–5.5(6.0) mm lato, flore tubuloso max. 3 mm non (3.1)3.8–4.6(5.0) mm longo, squama involucrali (0.9)1.0–1.5(1.9) non (0.8)1.8–2.2(2.5) lata, petiolo foliorum caulis inferiorum [(15)20–41(49) pro (13)16–21(22) mm] longiore, dentibus foliorum caulis inferiorum (1.0)1.5–2.7(3.0) mm non (2.7) 2.8–4.3 mm longis, foliis caulis superioribus longioribus [(18)19–28(33) pro (7)8–19(21) mm], differt. A L. monspeliensi (L.) H. J. Coste flore ligulato 2.5–3.8(4.8) non (3.3)3.4–3.9(4.0) mm lato, squama involucrali (0.9)1.0–1.5(1.9) non (1.2)1.3–1.9(2) mm lata, foliis basalibus longioribus [(31)32–68(80) vs. (16)17–29(32) mm] et latioribus [(19)22–40.8(58) vs. (9) 10–17.5 mm], pluribus dentibus praeditis [(24)25–72(78) pro (12)13–16(17)] et petiolo longiore [(32)38–96(103) pro (27)30–44(45) mm], foliis caulis inferioribus petiolum longiorem ferentibus [(15)20–41(49) pro (17)18–28(29)], differt.

Short-lived perennial herb (34)43–72(100) cm tall, sparsely hairy (especially on the lower part of stem and under the capitula), with rosettes arising from an aerial, oblique, violet woody rootstock, up to 20 cm long. Stems several, erect-decumbent, (0.9)1.0–3.3(6.0) mm thick at the base, divided above into several branches, each bearing 1 capitulum. Basal leaves (31)32–68(80) mm long, (19)22–41(58) mm wide, thin, hairless, ovate-spathulate, pinnatipartite or, rarely, bipinnatipartite, with dentate or deeply dentate margins and (24)25–72(78) teeth, which are (1.8) 2–4.5 mm long; petioles (32)38–96(103) mm long, withering at flowering. Lower cauline leaves (15)19–32(40) mm long, (9.5)12–21(25) mm wide, spathulate, pinnatipartite or, rarely, bipinnatipartite, with dentate or deeply dentate margins and (12)15–24(34) teeth, which are (1.0)1.5–2.7(3.0) mm long; petioles slightly winged, (15)20–41(49) mm long. Middle cauline leaves sessile, (21.5)23.7–47.9(59.0) mm long, (9)10–20(22) mm wide, oblong-linear, pinnatipartite or pinnatifid, with laciniate margins and (6)7–24(31) laciniae, which are (1.7)2.3–4.0(5.0) mm long. Upper cauline leaves sessile, (18)19–28(33) mm long, (2.0)2.7–8.0(9.0) mm wide, linear with laciniate margins and (3)4–9(11) laciniae, which are (1.2)1.6–3.0 mm long. Involucre (10.0)12.7–19.3(21.0) mm wide, with pluriseriate, triangular (external) to linear (internal), green phyllaries, (4.0)4.4–5.4(7.0) mm long, (0.9)1.0–1.5(1.9) mm wide, with brownish scarious margins. Receptacle glabrous, slightly convex. Capitula up to 53 mm in diameter. Ligulate florets up to 31, white, with tridentate apex, (8.5)10.0–17.6(20.0) mm long, 2.5–3.8(4.8) mm wide. Disk florets numerous, yellow, up to 3 mm long. Ray cypselae up to 3 mm, brown, with 10 whitish ribs and a tubulose crown-shaped pappus. Disk cypselae similar to ray cypselae, lacking pappus, (1.7)1.9–2.3(2.7) mm long, 0.70–0.74 mm wide, 0.55–0.61 mm thick.

Additional specimens examined (paratypes): — ITALY, Liguria. Rocchetta di Vara (province of La Spezia), on siliceous substrate ("diaspro"), 200–240 m a.s.l., 16 May 2008, D. Marchetti s.n. (PI!); Rocchetta di Vara (province of La Spezia), on siliceous substrate ("diaspro"), 200–240 m a.s.l., 17 May 2008, D. Marchetti s.n. (PI!); Rocchetta di Vara (province of La Spezia), on siliceous substrate ("diaspro"), 200–240 m a.s.l., 23 June 2010, M. Melai, D. Marchetti, R. Bernardello et G. Trombetti s.n. (PI!); Rocche di Valletti (province of La Spezia), on siliceous substrate ("diaspro"), 800 m a.s.l., 21 July 2010, M. Melai, D. Marchetti et R. Bernardello s.n. (PI!); Val Graveglia , sotto Nascio (province of Genova), Ponte di Lagoscuro , 250 m a.s.l., 21 July 2010, M. Melai, D. Marchetti et R. Bernardello s.n. (PI!) .

Ecology and Phenology: — Leucanthemum ligusticum grows in open rocky places (200–1060 m), on siliceous substrates and deep-oceanic siliceous sedimentary rocks ("diaspri"). It is a hemicryptophyte, flowering from the beginning of May until the first half of July.

Distribution: — Leucanthemum ligusticum is currently known from few localities in eastern Liguria (provinces of Genova and La Spezia; Fig. 3 ). Besides the three studied populations, the new species was observed near Bargone (Genova province), Mounts Roccagrande-Tregìn, 400–850 m and near the top of Mount Verruga, at 1060 m.

Karyology: —The new species is diploid, with 2n = 18 chromosomes, at all three localities studied (Liguria; Fig. 4A–C ). The karyotype formula is 2n = 2x = 18 = 2m sat + 4m + 2m sat + 8m + 2m sat at Ponte di Lagoscuro, 2n = 2x = 18 = 2m sat + 2m + 4m sat + 4m + 2m sat + 4m at Rocche di Valletti and 2n = 2x = 18 = 2m sat + 2m sat + 2m + 2m sat + 6m + 2m sat + 2m at Rocchetta di Vara ( Fig. 4D–F ). Chromosome size ranges from 3.60 to 6.5 µm.

Figures

FIGURE 1. Leucanthemum ligusticum sp. nov. General view of the plant (A); closeup of a capitulum in top view (B) and bottom view (C).

FIGURE 2. Leucanthemum ligusticum sp. nov. Variability of basal leaves in individuals from Ponte di Lagoscuro (A), Rocche di Valletti (B), Rocchetta di Vara (C). Variability of cauline leaves, upper ones (sx) to lower ones (dx), from Ponte di Lagoscuro (D), Rocche di Valletti (E), Rocchetta di Vara (F). Scale bars: 10 cm.

FIGURE 3. Leucanthemum ligusticum sp. nov. Known geographical distribution in eastern Liguria (northwestern Italy Italy).

FIGURE 4. Leucanthemum ligusticum sp. nov. Examples of metaphasic plates and relative haploid idiograms, from Ponte di Lagoscuro (A, D), Rocche di Valletti (B, E) and Rocchetta di Vara (C, F). Scale bars of metaphasic plates = 10 µm; scale bars of haploid idiograms = 1 µm.