Muhlenbergia caxamarcensis Laegaard & Sanchez Vega, Nordic J. Bot. 10:437. 1990.

Peterson, Paul M., Vega, Isidoro Sanchez, Romaschenko, Konstantin, Giraldo-Canas, Diego & Rodriguez, Nancy F. Refulio, 2018, Revision of Muhlenbergia (Poaceae, Chloridoideae, Cynodonteae, Muhlenbergiinae) in Peru: classification, phylogeny, and a new species, M. romaschenkoi, PhytoKeys 114, pp. 123-206 : 137

3. Muhlenbergia caxamarcensis Laegaard & Sanchez Vega, Nordic J. Bot. 10:437. 1990. Fig. 4A-C

Type.

Peru, Cajamarca, Micuypampa, 62 km from Cajamarca towards Celendín, 3600 m, 26 Mar 1988, S.A. Renvoize & S. Lægaard 4962 (holotype: CPUN!; isotypes: AAU!, K!, MO-3712393!, US-3185350!).

Description.

Loosely caespitose perennials. Culms 8-12 cm tall, 0.2-0.4 mm diameter just below the panicle, erect to decumbent near base, slender, scaberulous to glabrous, profusely branched below; lower internodes 5-10 mm long with repeated intravaginal branching. Leaf sheaths 4-27 mm long, glabrous, generally longer than the internodes, rounded near base; ligules (1.5-) 1.8-2.5 mm long, hyaline, often lacerate, margins decurrent, apex obtuse; blades 0.5-1.5 cm long, 0.6-1.2 mm wide, flat or folded, prominently veined, sometimes conspicuously crystalline or spiculate on both surfaces, otherwise glabrous below, sparsely scaberulous above and along margins, tapering to a boat shaped tip. Panicles (1.0-)1.5-4.0 cm long, 1-3 mm wide, exserted or included in the uppermost sheath, loosely contracted, narrow; primary branches 0.5-2 cm long, appressed to the culm axis, one per node. pedicels 1-5 mm long, stiff, densely scabrous, spiculate, erect; nodes 4-6 per inflorescence. Spikelets 2.4-2.8 mm long (excluding the mucro or awn), plumbeous to reddish-purple; glumes 1.2-1.6 mm long, shorter than the floret, subequal to equal, 1-nerved, glabrous, often reddish-purple near apex and greenish-grey below, apex obtuse; lemmas 2.4-2.8 mm long, lanceolate, keeled, prominently 3-nerved, dark reddish-purple to plumbeous above greenish-grey below, sericeous, lower ½ to ¾ with scattered appressed hairs, the hairs 0.3-0.5 mm long, apex acuminate, mucronate or short-awned, the awn up to 1.5 mm long, scabrous; paleas 2.4-2.6 mm long, as long as the lemma, lanceolate, hairy between the nerves; anthers 1-1.3 mm long, purple or yellow. Caryopses 0.9-1.1 mm long, elliptic to fusiform, terete, yellowish-brown.

Distribution.

This species is endemic to Peru, known only from Cajamarca and La Libertad departments.

Ecology.

Muhlenbergia caxamarcensis occurs on shallow soils on rock shelves and rocky outcrops often of calcareous origins, mud flats, open grassy meadows and slopes associated with Festuca , Carex , Calamagrostis (probably better treated as Cinnagrostis Griseb. but combinations are not yet made; Saarela et al. 2017, Soreng et al. 2017), Polylepis , Muhlenbergia ligularis , M. peruviana and M. cenchroides ; 3000-3600 m. Flowering March through May.

Comments.

Muhlenbergia caxamarcensis is morphologically similar to M. ligularis and M. fastigiata and can be separated from both of these species in possessing sericeous florets (lemma and palea) with hairs readily visible under 10 × magnification.

Muhlenbergia caxamarcensis is a member of M. subg. Bealia and is sister to the North American M. filiformis (Thurb. ex S. Watson) Rydb.- M. vaginata Swallen pair ( Peterson et al. 2010b). In our new analysis, M. caxamarcensis appears to have evolved within M. ligularis (Fig. 1A , plastid only). However, the ITS marker clearly aligns M. caxamarcensis with a single accession of M. ligularis (Fig. 1A ). This pair is sister to M. filiformis and all three accessions are sister to M. vaginata . These results suggest multiple origins for M. caxamarcensis from North and South American progenitors.

Specimens examined.

PERU. Cajamarca: Prov. Cajamarca, 16 km W of Cajamarca up road (Avenida Peru) towards Cumbemayo, 3440 m, 31 Mar 1997, P.M. Peterson & N. Refulio Rodriguez 14010 (US, USM); 18 km W of Cajamarca up road (Avenida Peru) towards Cumbe Mayo, 3600 m, 31 Mar 1997, P.M. Peterson & N. Refulio Rodriguez 14013 (US, USM); 29 km from Cajamarca on road to Celendín, S.A. Renvoize & S. Lægaard 4974 (AAU, CPUN, K, US); Cumbe Mayo, I. Sánchez Vega & W. Ruiz Vigo 598 (CPUN), I. Sánchez Vega 4690 (CPUN); Cumbe Mayo, W of Cajamarca, S.A. Renvoize 5000, 5004 & 5005 S. Lægaard & I. Sánchez Vega (AAU, CPUN, K, US); Micuypampa, 62 km from Cajamarca towards Celendín, S.A. Renvoize & S. Lægaard 4961 (AAU, CPUN, K, US); Prov. San Miguel, 61 km N of Cajamarca on hwy 3N towards Bambamarca, 3640 m, 16 Mar 2000, P.M. Peterson & N. Refulio Rodriguez 14916 (CPUN, US, USM); Cajamarca to Celendín, 3 km NE of Encañada, I. Sánchez Vega 2777, V. Torrel & E. Medina (CPUN); S.A. Renvoize & S. Lægaard 4849 (CPUN). La Libertad: Prov. Bolivar, 3 air km ESE of Longotea on road to Bolivar, 3202 m, 31 Mar 2008, P.M. Peterson 21965, R.J. Soreng & J. Montoyo Quino (US, USM); Nevado Cajamarquilla, 3500 m, 9 Sep 1946, J. Infantes Vera 937 (MOL).

Figures

Figure 1. A, B Maximum-likelihood tree inferred from combined plastid (ndhA intron, rps 16 - trnK, rps 16 intron, rps 3, and rpl 32 - trnL) and ITS sequences. Thick branches indicate posterior probabilities of 0.95 - 1; species in red occur in South America; scale bar = 2 %.

Figure 4. A-C Muhlenbergia caxamarcensis Laegaard & Sanchez Vega A habit B panicle branch C floret D-G Muhlenbergia ciliata (Kunth) Trin D habit E ligule F glumes G floret. Drawings A-C from Laegaard and Sanchez Vega (1990) from holotype collection (S. A. Renvoize & S. Laegaard 4962) D-G from Peterson and Annable (1991) drawn from P. M. Peterson & C. R. Annable 4541 (WS).