Limonium ilergabonum López-Alvarado, Cobacho, Arán & L. Sáez, 2017

López-Alvarado, Javier, Cobacho, Iris, Arán, Vicente J., Rosato, Marcela, Rosselló, Josep A. & Sáez, Llorenç, 2017, Limonium ilergabonum (Plumbaginaceae), a new species from northeastern Iberian Peninsula, Phytotaxa 331 (2), pp. 199-212 : 201-207

Limonium ilergabonum López-Alvarado, Cobacho, Arán & L. Sáez , sp. nov. ( Fig. 1 )

Type:— SPAIN. Catalonia, Tarragona province: Flix , 41°14’ 43”N 0°33’21”E, open scrub on gypsum marl, 45 m a.s.l., 31 August 2011, J. L. Alvarado, V. J. Arán & L. Sáez LS-7321 (holotype BC!; isotype MA!) ( Figs. 1 , 2 , 3 ) .

Diagnosis: Limonium ilergabonum is somewhat similar to L. hibericum , but differs by because leaves are narrower, width/length ratio =0.05–0.13 (vs. 0.28–0.54); the inflorescence shape is type A —according to Erben (1993) — (vs. type F or G) ; and calyx is longer (5.5–5.8 mm) (vs. 4.8–5.6 mm).

Description:— Perennial plant, usually with numerous robust stems. Caudices 0.5–4 cm long, densely spirally leafy. Leaves 20–110 × 3–9.8 mm, usually withered at anthesis, linear-oblanceolate, subacute or obtuse, without apiculum, 1(3)-nerved, papillate at least at the base; petiole slightly canaliculate, 1/2–2/3 as long as the blade. Stems 28–75 cm long, erect to suberect, papillose in the lower third. Inflorescence 22–63 × 7–21 cm, paniculate, type A, usually branched from the lower third. Branches of first order up to 21 cm long, loosely distichous, straight to arcuate, obliquely inserted (20–45°). Sterile branches present at the lower half of the stems. Spikes 2–17 cm long, erect to slightly arcuate, with 0.3–2.3 spikelets per cm. Spikelets 5–7.2 mm long, slightly curved, including 2–3(4) flowers. Outer bract 0.8–1.5 × 1–1.9 mm, glabrous, triangular to triangular-ovate, acute or obtuse, with a broad membranous margin; central part slightly fleshy part with the apex nearly reaching the margin. Middle bract 1.8–2.4 × 1.3–1.6 mm, oblong-ovate to oblong, hyaline-membranous. Inner bract 3.2–5.0 × 3.1–3.8 mm, glabrous, obovate-elliptic, obtuse, with a broad membranous margin; central part 2–3.5 x 1.6–2.4 mm, fleshy, obovate-oblong, with a tip 1–1.2 mm long, nearly reaching the margin. Calyx 5.2–5.8 mm long, exceeding the inner bract about 0.7–2.4 mm. Calyx tube hairy usually in one side, hairs c. 0.5 mm long; lobes 0.8–1 × 1–1.2 mm, triangular-ovate; tube ribs ending below the teeth base. Corolla infundibuliform; petals 7.5–8.8 × 1.8–2.4 mm, cuneate, entire to shallowly emarginate at the apex, pale violet. Pollen grains irregular in size, small-sized and misshaped, showing a finely reticulate exine. Stigma filiform, covered with narrow papillae.

Etymology:— The specific epithet refers to the Ilergabones, an ancient Iberian population who occupied the Ebro basin during the Pre-Roman period.

Ecology and distribution:— Limonium ilergabonum is currently known only from the type locality at Flix where it grows in open scrub on gypsum marl, between 35 and 50 m a.s.l. The species form a small population including only 30 individuals. Limonium hibericum grows intermingled with the new species. Additional species noted in the area were Retama sphaerocarpa ( Linnaeus 1771: 571) Boissier (1840: 144) , Tamarix africana Poiret (1789: 139) , Oryzopsis miliacea Linnaeus (1753: 61) , Helichrysum stoechas Candolle (in Lamarck & Candolle 1805: 132), and Rosmarinus officinalis Linnaeus (1753: 23) .

Conservation status:— Our observations indicate that L. ilergabonum should be listed as Critically Endangered CR D, following the categories and criteria of IUCN (2014), in view of its low population size (less than 50 individuals). The population is found near a road and it is likely that human-mediated disturbances may cause negative impacts on the species.

Morphometrics:— The multivariate ordination of 73 individuals using 21 morphological characters yielded two PCA components explaining 63.2% of total variance (33.5% for PC1 and 29.7% for PC2 axes). The characters contributing most to the first two PCA axes are shown in Table 2. Five non-overlapping groups could be recognised in the two dimensional PCA space ( Fig. 4 ). These discrete groups agree with the delimitation of the five taxonomic entities recognised in this study ( Fig. 5 ). According to the PCA ordination Limonium ilergabonum appears most closely related to L. hibericum . Specimens from both species could be separated along the first PCA axis, but they overlapped along the second PCA axis.

A second PCA including only the individuals of L. hibernicum and L. ilergabonum was performed and the results are shown in Fig. 6 . Again, individuals from the two species could be separated along the PC1 axis (explaining 52.3% of variance). The characters contributing most to the first PCA axis were the presence of papillae at the base of stems (0.952), the length of the inner bract (0.944), the length of the calyx (0.938), the length of the central part of the inner bract (0.887) and the length (0.872) and width (0.885) of the outer bracts.

Comparative morphology:— The main discriminant characters between L. ilergabonum and related species are shown in Table 3, and only a mention of the features supporting the recognition of the new species from L. hibericum are summarised here. The two species can be easily discriminated by the leaf shape (narrower and longer leaves in L. ilergabonum ; Fig. 3C–D ), the length and width of the outer bracts (0,6–1.4 × 0.8–2.2 mm in L. hibericum and 0.8–1.5 × 1–1.9 mm in L. ilergabonum ), the length of the whole inner bract (2.8–3.9 mm in L. hibericum and 3.2–5.0 mm in L. ilergabonum ), the length of the central part of the inner bract (1.7–2.4 mm in L. hibericum and in 2–3.5 mm L. ilergabonum ), the length of the calyx (4.8–5.6 mm in L. hibericum and 5.2–5.8 mm in L. ilergabonum ), and the presence of papillae at the scape basis and leaves ( L. ilergabonum ; Fig. 2E, F ). In addition, L. ilergabonum shows a different inflorescence shape (type A; Fig. 3A ) from L. hibericum (type F or G).

Pollen and stigma morphs:— The analysis of the pollen and stigma combination of the new species revealed that the population is monomorphic. All studied plants showed the B type combination (finely reticulate exine and a papillate stigma), suggesting a self-incompatible breeding system. Pollen viability values were very low (3.7%) and most pollen grains were irregular in size, small-sized and misshaped. On the contrary, the few stainable pollen grains were well-shaped and showed longer dimensions than the unstainable ones. In contrast, the sympatric individuals of L. hibericum showed plants with an A type combination (coarsely prominently reticulate exine and a cob stigma). This species also showed mostly irregular and unstainable pollen grains (up to 15%).

Chromosome number:— The chromosome number of 13 seedlings of L. ilergabonum and five of L. hibericum were determined. Limonium ilergabonum showed five individuals with 2 n = 18 chromosomes (diploid level) and five with 2 n = 27 chromosomes (triploid level) in all analysed cells. However, three seedlings showed each cells either with 2 n = 18 and 2 n = 27 chromosomes suggesting mixoploidy. In contrast, the five analysed individuals of L. hibericum showed a constant 2 n = 27 chromosome number.

Molecular data:— Seven fixed point mutations present in the ITS1 and ITS2 spacers were detected between L. ilergabonum and L. hibericum individuals ( Table 4). In addition, the two species differ by 12 mutations ( Table 5) from the plastid trnT -trnL spacer, of which six were point mutations and six were associated to length variants (indels).

Figures

FIGURE 1. Holotype of Limonium ilergabonum.

FIGURE 2. Morphology of calyx, bracts, and papillae from L. ilergabonum. A. Calyx. B. Outer bract. C. Middle bract. D. Inner bract. E. Scape papillae. F. Leaf papillae.

FIGURE 3. A. Inflorescences of Limonium hibericum (left) and L. ilergabonum (right). B. Spikes of L. ilergabonum. C. Leaves of L. ilergabonum. D. Leaves of L. hibericum.

FIGURE 4. Ordination of Principal Component Analysis for morphological characters of L. ilergabonum, L. hibericum, L. stenophyllum, L. catalaunicum and L. ruizii. PC1 = Principal Component 1. PC2 = Principal Component 2.

FIGURE 5. Map showing the known distribution of the studied species. Area within the line shows the distribution of L. hibericum. Star = L. ilergabonum; triangle=L. catalaunicum; black circle = L. ruizii; square = L. stenophyllum.

FIGURE 6. Ordination of Principal Component Analysis for morphological characters of L. ilergabonum and L. hibericum. PC1 = Principal Component 1; PC2 = Principal Component 2.