Parietaria cornuta Chamboul., Charrier & J.-F. Léger, sp. nov. (Fig. 1)

Type:— MOROCCO, Anti-Atlas: Province of Tata, Municipality of Tagmout, N29.97547 W8.25520 (WGS84), elev. 1080 m, cliff, 08 April 2013, M. Chambouleyron s.n. (holotype ECWP s.n.!; isotypes RAB114856!, P00878254!).

Diagnosis:— Differt a ceteris notis speciebus generis Parietariae [excl. Soleirolia soleirolii (Req.) Dandy ≡ Parietaria soleirolii (Req.) Spreng.] cornibus perianthi florum feminorum. Differs from all other known Parietaria [excl. Soleirolia soleirolii (Req.) Dandy ≡ Parietaria soleirolii (Req.) Spreng.] species by the horns of its female flower perianth.

Description:—Therophyte (annual), up to 20 cm tall. Stem terete, greenish to reddish, densely hairy, bearing two types of whitish to yellowish erect hairs, long hairs straight, 0.3–0.6 mm long, short hairs hooked, up to 0.1 mm long. Leaves 5–34 × 3–30 mm, alternate (spirally arranged), broadly ovate to elliptic, hairs scattered on both surfaces, long hairs straight, 0.3–0.9 mm long, short hairs hooked, up to 0.1 mm long; abaxial surface pale green, adaxial surface dark to pale green; base cuneate to truncate; margin entire, apex obtuse to ± acute; petiole accrescent, up to 33 mm long, densely hairy with hairs similar to those on stems. Inflorescence in axillary clusters, each axil bearing two different ones: a cluster of (1–)2–5(–7) pedicelled functionally male flowers, a cluster of 1–2(–7) sessile female flowers. Bracts subtending only functionally male flowers, 0.9–1.7 × 0.2–0.4 mm, oblong, with long straight and short hooked hairs. Flowers with long straight and short hooked hairs; functionally male flowers 1.2–1.3 mm long, perianth tube campanulate, with 4 apical triangular acute lobes 0.4–0.5 mm long, whitish to greenish with red to purple veins, pistillode yellow; female flowers accrescent, 1.6–2.3 × 1.4–2.9 mm, pyriform, with (3–)4–5(–6) basal horns of 0.5–1.3 mm long (sometimes irregular on same perianth), pale yellowish to greenish with reddish veins on outer surface; female pericarp dehisce into individualised parts (apical lobe + corresponding part of the tube + horn). Stamens 4, anthers oblong, 0.6–0.8 mm long. Style 1, slender, exserted, brownish. Stigma claviform, fimbriate, brownish. Achenes 1 per fruit, 1.3–1.5 × 0.8 mm, narrowly ovoid, brownish, shiny.

Phenology:— Flowering between at least January–April, but the flowering period has not been surveyed from May to December.

Rank:— Within the genus Parietaria, the perianth basal horns is a feature sufficient to justify species rank for this taxon.

Etymology:— This new species name refers to the horns (cornu, - us, in Latin) of the female flower perianth.

Ecology:— On shaded calcareous rocks (nevertheless its presence on an acidic substrate cannot be ruled out, as these rocks are present in the region), at elev. 950–1250 m (according to our records). This area receives a cumulative annual rainfall of ca. 100–400 mm /year (after Roux et al. 1949), with significant inter-annual variability (occasional dry years with less than 50 mm of rainfall), which corresponds to an arid bioclimate (sensu Emberger 1955).

Known distribution:— Up to now, Parietaria cornuta is only known from the central Anti-Atlas (AA-3, sensu Fennane & Ibn Tattou 2005), from where it may be endemic; one locality is close to the limit of western Anti-Atlas (AA-1) (Fig. 2).

Conservation status:— This new Parietaria appears to be mainly distributed in the central Anti-Atlas, where it was found in an area of ca. 1200 km ². Although several field expeditions were dedicated to this area and other parts of the Anti-Atlas, no additional locations were found. However, extra field surveys should be undertaken to gain a better knowledge of its distribution. Its populations can reach several dozen individuals per cliff. Due to the lack of data on the potential size reduction of its populations, and/or on its geographic range fluctuation/decline/fragmentation, and/or on its number of mature individuals declining, a threat category according to the IUCN guidelines (IUCN 2024) cannot be assigned. However, regarding its chasmophytic ecology, which is less threatened by human activities, it is proposed to assign the status ‘Least Concern’ (LC) to this new species. It could also be listed in the same category and as an endemic taxon (E) in the Red Book of Moroccan Plants (Fennane 2021).

Additional specimens investigated (paratypes): — MOROCCO, Anti-Atlas: Province of Taroudant, Municipality of Sidi Ahmed Ou Abdellah, N30.33254 W8.56375, elev. 1050 m, cliff, 14 March 2015, M. Chambouleyron s.n. (CHAMB s.n.!, G00628219!); ibid, 07 April 2013, M. Chambouleyron s.n. (CHAMB s.n.!); ibid, 11 February 2021, M. Chambouleyron s.n. (ECWP s.n.!); Province of Tata, Municipality of Tamanarte, N29.08397 W9.18668, elev. 1010 m, cliff, 30 January 2019, M. Charrier s.n. (ECWP s.n.!); Province of Tata, Municipality of Tizaghte, N29.64247 W8.48002, elev. 1030 m, cliff, 01 February 2019, M. Charrier s.n. (ECWP s.n.!); Province of Tata, Municipality of Tizaghte, N29.54806 W8.45955, elev. 1020 m, cliff, 11 February 2019, M. Charrier s.n. (ECWP s.n.!); Province of Tata, Municipality of Tigzmerte, N29.70135 W8.45631, elev. 1000 m, cliff, 14 February 2019, M. Chambouleyron s.n. (ECWP s.n.!).