Poa pratensis agassizensis (B. Boivin & D. Loeve ) Roy L. Taylor & MacBryde, Canad. J. Bot. 56(2): 193. 1978.

Soreng, Robert J. & Peterson, Paul M., 2012, Revision of Poa L. (Poaceae, Pooideae, Poeae, Poinae) in Mexico: new records, re-evaluation of P. ruprechtii, and two new species, P. palmeri and P. wendtii, PhytoKeys 15, pp. 1-104 : 46

16a. Poa pratensis agassizensis (B. Boivin & D. Loeve) Roy L. Taylor & MacBryde, Canad. J. Bot. 56(2): 193. 1978. Fig. 17 A-C

Poa agassizensis B. Boivin & D. Löve, Naturaliste Canad. 87(6-7): 176-180, f. 1-2. 1960. Type: Canada, Manitoba, MacDonald Co, 6 Jun 1952, B.Boivin, Löve & Alex 9167 (holotype DAO!; isotype: US-2553819!).

Description.

Tufts sparse, some shoots clustered; pale green or bluish-gray-green; tillers intra- and extravaginal. Culms 20-40(-50) cm tall. Ligules of lower culm and tiller leaves commonly glabrous abaxially; lades of cauline leaves flag leaf blades folded, with involute margins, moderately thick, moderately firm; sterile shoot blades usually less than 10 cm long, 0.8-2 mm wide, all folded with involute margins, sparsely pubescent adaxially. Panicles 4-6(-8) cm long, erect or nodding, or loosely contracted or open, ovoid to narrowly pyramidal; rachis with 2-3(-5) branches per node; primary branches steeply ascending to ascending, smooth or sparsely to moderately densely scabrous; longest 1-2.5(-3) cm, with several spikelets per branch. Spikelets lanceolate, not bulbiferous; glumes unequal, glaucous or not; lower glumes 1(-3)-veined; upper glumes shorter than or nearly subequaling the lowest lemma; lemmas 2-3(-3.5) mm long, finely muriculate, intermediate veins glabrous; paleas scabrous, medially glabrous over the keels, intercostal region glabrous. Anthers frequently sterile. 2 n = 41, 42, 43, 56.

Distribution.

This subspecies in North America is known from Canada and USA, and in Mexico from the states of Baja California and Coahuila.

Ecology.

The subspecies inhabits cool temperate prairies, meadows, and open coniferous forests.

Specimens examined.

Mexico. Baja California: Municipio Ensenada, Paraje El Rayo Ejido, 1000 m, 13 May 1997, A.Miranda 1153 (MEXU). Sierra San Pedro Mártir, La Gurulla, 30°54'N, 115°29'W, 2050 m, 29 Jun 1982, R.Moran 30956 (MEXU, TAES). Coahuila: Sierra de Arteaga, Las Vigas, Canon de la Carbonera, 25°20'N, 100°39'W, 2100 m, 5 Jun 1987, J.A.Villarreal 3800 & M.A.Carranza (TAES). Municipio Arteaga, Ejido La Escondida, 25°23'30"N, 100°33'15"W, J.A.Garcia 49 (MEXU).

Discussion.

This form of Poa pratensis , originally described as a species indigenous to Canada and the United States (Boivin and Löve 1960) and now accepted as Poa pratensis subsp. agassizensis, is probably indigenous, but morphologically is questionably distinct from the Eurasian elements of Poa pratensis subsp. angustifolia, or xeric forms of cultivated Poa pratensis subsp. pratensis ( Soreng 2007). As originally described it is a taxon with short, ovoid panicles, with small spikelets, and involute leaves. Such specimens are not uncommon among early herbarium collections across Canada and the USA. It approaches Poa pratensis subsp. angustifolia closely, but that subspecies of Eurasian origin has looser panicles, and is generally a lower polyploid ( Stoneberg-Holt 2004). Separation of Poa pratensis subsp. agassizensis from Poa pratensis subsp. pratensis is difficult, and so far there is no molecular or cytological data to support it as a separate taxon. We recognize Poa pratensis subsp. agassizensis as a marginally distinct taxon, and site a few vouchers that best match this form.

Figures

Figure 17. Poa pratensis L. A-C Poa pratensis subsp. agassizensis (B. Boivin & D. Loeve) Roy L. Taylor & MacBryde A habit B sheath, ligule, blade lateral view C branch segment with spikelets D-G subsp. alpigena (Lindm.) Hiitonen D habit E inflorescence F branch segment with spikelets G palea H, I subsp. angustifolia (L.) Lej. H habit I branch segment with spikelets. Drawings from Soreng (2007).