Amaranthus × romanus Iamonico

Iamonico, Duilio, 2017, Amaranthus × romanus (Amaranthaceae), a new hybrid from Italy, Phytotaxa 295 (1), pp. 89-91 : 89

Amaranthus × romanus Iamonico , hybr. nov. ( Amaranthus cruentus L. × Amaranthus retroflexus L.)

Type:— ITALY: Roma, Largo Preneste, 24 August 1964, Cacciato 3 (holotype RO!) ( Fig. 1 ).

– “ Amaranthu s × galii ” sensu Cacciato (1966: 628).

Diagnosis:— Herbs monoecious, annual (therophyte). Stems erect, green, slightly pubescent, branched. Leaves green, ovate to ovate-lanceolate, rhomboidal, margins entire or undulate, apex acute or obtuse (sometimes slightly emarginate), mucronate, base cuneate, usually glabrous, petioled. Synflorescences terminal, panicle-like. Floral bracts lanceolate, longer than perianth (3 ‒ 4 mm long), acute, slightly awned, with membranous borders narrowing to apex, margins entire, glabrous. Pistillate flowers mostly abortive with 5 obovate-spathulate tepals 2.5 ‒ 3.5 mm long. Fruit ellipsoidals, dehiscent. Seeds lenticular, dark-brown or reddish-brown.

Etymology:— The specific epithet is dedicated to the city of Rome, which is the locus classicus of this nothotaxon.

Morphological comparison with parental taxa:— Amaranthus × romanus differs from A. cruentus in having its stem more pubescent, the synflorescence with more densely arranged paraclades, and longer floral bracts. In comparison to A. retroflexus , A. × romanus has intensely green and less pubescent stems (never tomentose), and synflorescences with paraclades and main florescences that are longer and narrower.

Alien status:— Hybrid probably arisen in Europe ( Italy?).

Occurrence in Europe:— On the basis of the current knowledge, Amaranthus ×romanus is known in Europe with certainty only from Central Italy (Lazio region; see Iamonico 2015). The name “ Amaranthus × galii ” is also listed in the floras of three other European countries: Spain (Sennen 1929), France ( Tela Botanica 2000), and Hungary ( DAISIE 2008). However, further investigations (i.e. examination of herbarium specimens and analyses of local literature) are needed to verify the occurrence of A. ×romanus against A. ×ozanonii in France and Hungary.

Additional specimens seen:— ITALY. Lazio: Roma, Largo Preneste , 25 August 1957, Cacciato 3 ( RO!) ; Roma, lungo la via Frascati , 12 August 1964, Cacciato s.n. ( RO!) ; Roma, macerie sul ponte la stazione ferr. Prenestina , 20 August 1964, Cacciato s.n. ( RO!) ; Roma, a via Frascati , 19 September 1964, Cacciato s.n. ( RO!) ; Roma, lungo la via Demetriade nei pressi del Quadraro , strada assai polverosa, 2 October 1964, Cacciato s.n. ( RO!) ; Roma, aiola incota in Piazza dei dicembrini nei pressi

1 According to Stafleu & Cowan (1976: 76), the pages 1 ‒ 80 of the volume 5(2) of Synopsis der Mitteleuropaischen Flora was published on 30 July 1920. di Cinecittà, 08 October 1964, Cacciato s.n. ( RO!) ; Roma, su marciapiede sterrato i Via Curzio Rufo a Cinecitta, 10 October 1964, Cacciato s.n. ( RO!) ; Roma, Cinecitta, 14 August 1965, Cacciato s.n. ( RO!) ; Roma, 28 August 1965, Cacciato s.n. ( RO!) ; Roma, 20 September 1966, Cacciato s.n. ( RO!) ; Roma, prati a Centocelle, 10 September 1989, Cacciato s.n. ( RO!) .

Figures

FIGURE 1. Holotype of Amaranthus ×romanus Iamonico (RO!).