342609 Poa pratensis L.
- L., Sp. Pl.: 67 (1753). Neotype (BM): European Russia: Prov. Sanct-Petersburg, "5 km australi-occidentem versus a st. viae ferr., Mga, pratulum ad ripam dextram fl. Mga", 26. July 1997, leg. N.N. Tzvelev 257 typ. cons. (Soreng and Barrie 1999: 157-159).
Notes: Poa pratensis s. lat. is another partly or mainly agamic complex (many studies from Müntzing 1932, 1940 and onwards) treated in several ways in different traditions. The limits between the taxa (agamospecies) are unclear and some reticulation is probable.
Many Russian authors (e.g., Tzvelev 1964b, 1976, PAF proposal) and western and central European ones (e.g., Edmondson 1980; Hämet-Ahti et al. 1998) have treated P. pratensis s. lat. as a series of species, sometimes with subspecies. Many Scandinavian (e.g., Hylander 1953b; Elven 1994; Mossberg and Stenberg 2003; Elven et al. 2005) and North American authors (e.g., Soreng et al. 2003; Soreng 2007) have treated it as one species with several subspecies, one or more of these probably arbitrarily circumscribed ("alpigena", perhaps "irrigata"). The same considerations as to species vs. subspecies are relevant here as in P. arctica. We agree, however, that there may be four or five main, widespread groups to be considered in the northern regions - under the names "pratensis" s. str., "angustifolia", "alpigena", "irrigata" (= "humilis" = "subcaerulea"), and perhaps "colpodea" - and in addition some less well-known or less widespread plants.
Haugen and Elven: One reason why P. pratensis s. lat. is problematic in the north is that the distinctions from P. arctica s. lat. sometimes become obscure, at least in viviparous plants. Taxa from both complexes may partake in a highly polyploid and agamospermous superstructure. In Svalbard, Haugen (2000) compared, among other Poas, plants of P. pratensis subsp. alpigena and subsp. colpodea and P. arctica subsp. arctica and subsp. caespitans. She investigated morphology in ca. 50 characters, reproductivity, and isoenzymes as molecular markers. She found that P. pratensis subsp. alpigena and P. arctica subsp. arctica were insufficiently distinct in most morphological characters except lemma hairiness. They were also less distinct in isoenzymes than expected of two species from different complexes. Subspecies caespitans was slightly more distinct from subsp. arctica in morphology than the latter was from P. pratensis subsp. alpigena. Subspecies caespitans was distinct also in isoenzymes, although most similar to subsp. arctica. Poa pratensis subsp. colpodea was fairly distinct from all others in both morphology and isoenzymes. In morphology, subsp. colpodea was a little more distant from subsp. alpigena than subsp. alpigena was from P. arctica subsp. arctica, even if it shared the lemma pubescence of subsp. alpigena. In isoenzymes, subsp. P. pratensis subsp. colpodea was more similar to subsp. alpigena than to P. arctica subsp. arctica. We suspect that subsp. colpodea may be a hybridogeneous offspring from P. arctica s. lat. and P. pratensis s. lat., morphologically uniform and widespread (due to bulbil reproduction) in the High Arctic. Other hybridogeneous offsprings could be expected.
We accept five subspecies of P. pratensis and an additional species treated at "acceptance level 1" by Soreng et al. (2003) and Soreng (2007): P. sublanata. As subspecies may not be the most appropriate category, the taxa might be better treated as species. We enter provisionally an additional Russian subspecies, subsp. zhukoviae, and a species suggested by Tzvelev (1976) possibly to be a hybrid offspring, P. raduliformis.