Friday, December 29, 2017

[Botany • 2017] Taxonomic Revision of Rhodalsine (Caryophyllaceae): A Plant that Linnaeus Forgot

Rhodalsine geniculata  (Poir.) F. N. Williams

in Kool & Thulin. 2017.

The mainly Mediterranean genus Rhodalsine (Caryophyllaceae) is revised and a single species, R. geniculata, is recognized, distributed from the Canary Islands in the west to Somalia in the east. The history of the taxon, which was known already during the 17th century but entirely overlooked by Linnaeus, is outlined. Variation and taxonomy are discussed and illustrations and a distribution map are provided. Many names are placed in synonymy and most of the names are typified, including six lectotypes designated here.

Keywords: Caryophyllaceae, Mediterranean region, Minuartia, nomenclature, Rhodalsine, Sperguleae, taxonomy, typification

Fig. 1. Flowers of Rhodalsine geniculata from Spain, Lagunas de La Mata, Torrevieja, April 2012

 photograph by Marta Rubio-Texeira.

Rhodalsine J. Gay in Ann. Sci. Nat., Bot., sér. 3, 4: 25. 1845 
= Alsine sect. Rhodalsine (J. Gay) Boiss., Fl. Orient. 1: 671. 1867 
= Minuartia subg. Rhodalsine (J. Gay) Graebn. in Ascherson & Graebner, Syn. Mitteleur. Fl. 5(1): 774. 1918. 

— Type: Rhodalsine procumbens (Vahl) J. Gay, nom. illeg. superfl. (=Arenaria procumbens Vahl).

Description — Herbs perennial or sometimes annual, with indumentum of glandular hairs. Leaves opposite, without stipules, but leaves of each pair with shortly connate bases. Flowers in lax cymes. Sepals 5, connate at base into a short hypanthium. Petals 5, pink or white, inserted at apex of hypanthium, shortly clawed at base. Stamens 10, in 2 whorls, those of outer whorl inserted at base of petals, those of inner whorl antisepalous, inserted on a low, ring-shaped rim surrounding base of ovary; pollen trizonocolpate. Ovary shortly stipitate, subglobose, thin-walled; styles 3, filiform. Capsule opening by 3 valves. Seeds many, orbicular-reniform, wingless; radicle of embryo accumbent. Chromosome base number x = 9.

Distribution — A genus of a single variable species distributed in the Canary Islands, around the Mediterranean and in the Horn of Africa region.

Rhodalsine geniculata (Poir.) F. N. Williams in Bull. Herb. Boissier 6:7.1898
 ≡ Arenaria geniculata Poir., Voy. Barbarie 2: 166. 1789 
Alsine geniculata (Poir.) Strobl in Oesterr. Bot. Z. 35: 212. 1885 
Minuartia geniculata (Poir.) Thell. in Mém. Soc. Sci. Nat. Cherbourg 38: 232. 1912 
Cherleria geniculata (Poir.) Samp., Lista Herb. Portug.: 82. 1913. 

— Holotype: without locality, [Poiret] s.n. (P-LA! [P00287174]).

Distribution and ecology — Rhodalsine geniculata is known from Portugal, Spain (including the Canary Islands, Melilla and the Balearic Islands), Gibraltar, Italy (including Sardinia, Sicily, Pantellaria and Linosa), Malta, Greece, Cyprus, Morocco, Algeria, Tunisia, Libya, Egypt and Somalia (Fig. 3). It occurs in sandy, stony or rocky places from near sea level up to 2050 m. In most of its range it is found at elevations below 600–700 m and it is often confined to habitats on or close to sea shores. However, in Morocco the species is also found at elevations up to about 1500 m in the Atlas Mountains, whereas in Somalia the known altitudinal range is 1350–2050 m.

Anneleen Kool and Mats Thulin. 2017. A Plant that Linnaeus Forgot: Taxonomic Revision of Rhodalsine (Caryophyllaceae). Willdenowia. 47(3);  317–323.  DOI: 10.3372/wi.47.47313

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