(1391) Proposal to conserve the name Poa pratensis (Gramineae) with a conserved type

Abstract

Although the name Poa pratensis has been in continuous use since 1753, its application is complicated by the taxon's extreme variation in morphology and cytology (2n = 22-147, including most intermediate numbers: Grant, P1. Speciation, ed. 2: 431. 1981), the predominance of facultative agamospermous and rhizomatous clonal reproduction, and world-wide distribution due to both native occurrence and introductions for lawns, forage and soil stabilisation, and as a ruderal. In its broadest sense, P. pratensis is treated as a complex encompassing a number of ecotypic variants. But there is also a tradition going back to Linnaeus of recognising the variants of P. pratensis s.l. as distinct species; one, P. angustifolia L., also dates from 1753. As noted by Edmondson (in Tutin & al., Fl. Eur. 5: 161. 1980), the taxa within the P. pratensis group have probably arisen on more than one occasion through hybridisation events but today rarely intercross and, within the limitations of their breeding system, can therefore be regarded as species. Sherif & Siddiqi (in El-Gadi, Fl. Libya 145: 64. 1988) designated Herb. Linn. No. 87.16 (LINN) as the lectotype of Poa pratensis L. (as Type, see Art. 7.11 of the Code). This specimen, annotated 5 (the species number of P. pratensis in Species plantarum) in Linnaeus's hand, is one of the original elements for the name. As the specimen is original material and does not conflict with the protologue, Sherif & Siddiqi's lectotypification cannot be superseded under Art. 9.11 of the Code. Unfortunately, the lectotype clearly does not belong to P. pratensis as currently conceived, but to its circumboreal counterpart, P. alpigena (Fr. ex Blytt) Lindm. (Sv. Fanerogamfl.: 91. 1918). The following characters identify the lectotype as Poa alpigena s.str.: a short panicle with branches smooth or very sparsely scabrous and few-flowered, the branches occurring in pairs at the lower panicle nodes; spikelets relatively small, glumes pruinose, sparsely scabrous, quite long but distinctly shorter than the first lemma; slender habit with culms single from a rhizome, without intravaginal lateral shoots; blades folded, short, and less than 1.5 mm wide. P. subcaerulea Sm. (= P. pratensis subsp. irrigata H. Lindb.), a related member of the complex, is similar to P. alpigena, but its spikelets are generally larger, with glumes that are nearly as long as the first lemma, often more densely scabrous; the blades are broader, up to 3 mm wide; and the habit is more stout. P. angustifolia, a third element commonly recognised in the complex, has spikelets like P. alpigena, but larger more densely flow-