Muhlenbergia romaschenkoi P.M. Peterson, 2018

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 : 177-179

18. Muhlenbergia romaschenkoi P.M. Peterson sp. nov. Fig. 12A-L

Type.

Peru. Depto. Huánuco, Pachitea, 21 air km NE of Huánuco, 7 km E of Puerto Rancho jtn on road to Panao, along Río Huallaga, 9°49'45.9"S, 76°3'12.9"W, 2094 m, 6 Mar 2007, P.M. Peterson 20331, R.J. Soreng & K. Romaschenko (holotype: US-3730646!; isotypes: MO!, USM!).

Description.

Loosely caespitose to densely tufted, annuals to short-lived perennials with delicate bases, flowering the first year. Culms 20-40 cm tall, erect or decumbent at the base, branching at the lower and middle nodes, scaberulous below the terete nodes; internodes generally 2.0-9.5 cm long. Leaf sheaths 4.0-7.5 cm long, glabrous or scaberulous, commonly shorter than the internodes; ligules 1.2 –3.0(– 5.0) mm long, hyaline, apex acute to obtuse, often lacerate with age; blades 3-12 cm long, 1.2-2.5 mm wide, flat or loosely involute, scaberulous to glabrous below and scabrous above. Panicles 7-15 cm long, 0.6-2 cm wide, narrow and contracted to loosely spreading, interrupted below, terminal and axillary, 15-23 nodes per panicle; primary branches 3.5-7.5 cm long, usually one per node, when immature the branches mostly appressed and ascending, when mature the branches sometimes widely spreading up to 50° from the rachises; pedicels 1-3 mm long, usually shorter than the spikelets, antrorsely scabrous, stout, appressed. Spikelets 2-4 mm long, erect, stramineous to purplish; glumes 1-2.8 mm long, unequal, 1-nerved, scabrous along the nerves, apex acute to acuminate, often mucronate or erose, the mucro up to 0.5 mm long; lower glumes 1-2.0 mm long; upper glumes 1.5-2.8 mm long, more than ½ as long as the lemma; lemmas 2.0 –3.5(– 4.0) mm long, lanceolate, widest near base, awned, scaberulous above and villous on proximal 1/2 along the margins and the midvein, the hairs 0.5-1.5 mm long, callus short-pubescent, the awn 10-30 mm long, scabrous, flexuous; paleas 1.8 –3.4(– 3.8) mm long, lanceolate, sparsely appressed pubescent between the nerves on the proximal ½; anthers 0.3-0.4 mm long, purplish, yellow with age. Caryopses 1.0-2.2 mm long, narrowly fusiform, terete, brownish.

Distribution.

Endemic to Peru and known only from Huánuco.

Ecology.

Muhlenbergia romaschenkoi grows on rocky slopes and limestone rock outcrops in grasslands with Aristida adscensionis , Bidens , Bothriochloa , Eragrostis nigricans (Kunth) Steud., Eupatorium , Melinus minutiflora , Microchloa kunthii Desv., Muhlenbergia ciliata , M. rigida and Nassella ; 1800-2500 m.

Etymology.

We honour Dr. Konstantin Romaschenko (born 1969) who accompanied PMP and Robert J. Soreng on the collecting trip in which material of the species was gathered.

Comments.

Muhlenbergia romaschenkoi can be separated from M. microsperma in having longer acute to acuminate glumes (1-2.8 mm long) and by lacking cleistogamous panicles present in the axils of the lower sheaths. Muhlenbergia tenuifolia (Kunth) Kunth, a species ranging from southern Arizona, New Mexico and Texas, U.S.A., throughout México and then again in Venezuela, Bolivia and Argentina, is morphologically similar to M. romaschenkoi but differs in having yellowish anthers 0.9-1.5 mm long ( Peterson and Annable 1991; Peterson 2003; Peterson et al. 2007b; Peterson and Giraldo-Cañas 2011, 2012). Initially we thought the new species was M. tenuiofolia with immature anthers 0.3-0.4 mm long. However, our collection of M. romaschenkoi includes well-developed florets with mature caryopses and anthers. Therefore, the observed small anthers in M. romaschenkoi are not a result of immaturity but represent a genetic difference, from M. tenuifolia , which is not known in Peru.

Muhlenbergia romaschenkoi , a member of M. subg. Muhlenbergia , is sister to M. spiciformis Trin. (plastid marker), a species known from south-western United States and throughout Mexico whereas ITS marker aligns it within the M. tenuifolia clade (Fig. 1B ). Muhlenbergia spiciformis differs from the new species in having shorter glumes 0.3-1 mm long and larger anthers 0.9-1.6 mm long ( Peterson 2003; Peterson et al. 2007b). These results suggest multiple origins for M. romaschenkoi from North and South American progenitors. Similar to M. caxamarcenis , this scenario appears to be a common pattern of speciation for South American species of Muhlenbergia , needing further study.

Specimen examined.

Peru. Huánuco: between Huánuco and Tingo María, vereda Taruka, 17 km NE of Huánuco in valley of Río Huallaga, T. Croat 57781 (MO).

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 12. Muhlenbergia romaschenkoi P. M. Peterson A habit B ligule C spikelet D lower glume E upper glume F lemma, lateral view G lemma, dorsal view H palea, dorsal view I palea, lateral view J palea, ventral view K lodicules, stamens, and pistil L caryopsis. Drawings from the holotype collection P. M. Peterson, R. J. Soreng & K. Romaschenko 20331.