A revision of Poa subsection Aphanelytrum (Poaceae, Pooideae, Poaeae, Poinae); and a new species, Poa auriculata

Abstract In this study the peculiar Andean grass genus Aphanelytrum, with two species, is reduced to Poa subsect. Aphanelytrum comb. & stat. nov. A third species, Festuca reclinata, is assigned to the subsection, which shows states transitional between a more typical Poa and Aphanelytrum. Poa subgen. Poa supersect. Homalopoa sect. Dioicopoa subsect. Aphanelytrum comb. & stat. nov. is characterized in having stooling perennials with decumbent to spreading culm bases that continuously branch and often root at low to mid-culm nodes, glabrous spikelets with long rachillas 1.2–4.2 mm long, short glumes less than ½ the length of the florets, and lemmas with bifid apexes that are mucronate to short-awned. We provide for the three species taxonomic discussions, morphological and anatomical descriptions, keys, illustrations, and a list of specimens. Also, we provide two new names, Poa hitchcockiana nom. nov. and Poa sanchez-vegae nom. nov., and one new combination, Poa reclinata comb. nov. A new species, Poa auriculata sp. nov. from Peru, not thought to be a member of Poa subsect. Aphanelytrum, is presented. It is the first in the genus with prominent auricles. In addition, we place Poa apiculata in Poa subgen. Poa supersect. Homalopoa sect. Dioicopoa subsect. Tovarochloa comb. & stat. nov.

Th e placement and evolutionary relationships of Aphanelytrum have been controversial since its inception. It was originally placed in the subfamily "Festuceae" [Festucoideae], applied in the broad sense of Bentham (1881), Hackel (1887), and Hitchcock (1935). Hackel mistook the upper individual fl orets for single-fl owered spikelets and placed Aphanelytrum in Brachyelytrum [ B. procumbens ] within tribe Agrostideae, subtribe Stipinae. Chase (1916) reinterpreted the spikelet morphology, and placed the genus between the subtribes Melicinae and Centothecinae, which at that time were considered adjacent subtribes of the subfamily Festucoideae, tribe Festuceae. After major realign-ments of the classifi cation of the Poaceae (e.g. Clayton and Renvoize 1986), the genus was placed in a much more narrowly defi ned subfamily Pooideae (syn. Festucoideae), tribe Poeae (syn. Festuceae) near Poa L. (Clayton and Renvoize 1986). Aphanelytrum and Poa have very similar leaf anatomical characteristics, as well as multi-fl owered, membranous spikelets with 5-veined, keeled lemmas, glabrous ovaries, and caryopses with an oval hilum (Clayton and Renvoize 1986;Clayton et al. 2006). In the most recent Poaceae classifi cation (e.g. Soreng et al. 2015) Aphanelytrum is placed as a synonym of Poa in the subtribe Poinae, as suggested in studies by Gillespie et al. (2008), Soreng et al. ( , 2015, Soreng and Peterson (2012), and Refulio Rodriguez et al. (2012).
Based on ITS sequences, Gillespie et al. (2008) found the monotypic Tovarochloa ( T. peruviana T.D. Macfarl. & P. But) to be a weakly supported sister of Aphanelytrum procumbens and A. peruvianum . In a plastid trn-TLF derived tree, Refulio Rodriguez et al. (2012) verifi ed this result showing a strongly supported Aphanelytrum procumbens sister to Tovarochloa, and published a section in Poa for Tovarochloa (nom. inval.; later validated as P. sect. Tovarochloa (T.D. Macfarl. & P. But) Molinari, see Molinari-Novoa 2015), but they left the genus Aphanelytrum unplaced within Poa . Tovarochloa peruviana is a small, delicate and diminutive annual species with 1-fl owered spikelets that was previously linked to Dissanthelium Trin. (Clayton and Renvoize 1986;Macfarlane and But 1982;Tovar 1993), now both are included within Poa Gillespie et al. 2008;Refulio Rodriguez et al. 2012;Soreng et al. 2015). Giussani et al. (in press) estimated the time of divergence of Tovarochloa and Aphanelytrum at between 1.24 and 5.05 mya.
Festuca reclinata Swallen, known only from the Páramo del Almorzadero in the Cordillera Oriental of Colombia, has been linked to Aphanelytrum based on exhibiting similar morphologies (Stančík and Peterson 2007;Sánchez Vega et al. 2007). Th e growth habit, panicles, and spikelet characteristics of F. reclinata are strikingly similar to those found in A. peruvianum and A. procumbens (Sánchez Vega et al. 2007). All three species have weak, decumbent culms with intravaginal branching, narrow fewspikeleted panicles, spikelets with long fl exuous rachillas, and small glumes. In comparison with F. reclinata, A. peruvianum has smaller lemmas (2.2−3.5 mm vs. 7−8.5 mm in F. reclinata ), smaller anthers (2−2.9 mm vs. 3.5−3.8 mm), and shorter spikelets (5−7 mm vs. 10−13 mm) [Sánchez Vega et al. 2007]. Th e strongly keeled lemmas in F. reclinata do not agree with its placement in Festuca (Sánchez Vega et al. 2007). Also like Aphanelytrum and Poa , F. reclinata has fused sheath margins, terete rachillas (vs. dorsoventrally compressed in Festuca ), and lacks the thickened annulate callus typical of Festuca . Aphanelytrum procumbens has a caryopsis with short elliptical hilum, less than 1/5 the grain in length (typical of Poa vs. linear and proportionally longer in Festuca ), but caryopses have not been observed in A. peruvianum or F. reclinata .
Th e main goal of this study is to present a systematic revision Poa subsect. Aphanelytrum comb. & stat. nov. that includes three species. We make a new combination for F. reclinata , and provide new names for Aphanelytrum procumbens and A. peruvianum . In addition, we include a key to the species, complete descriptions, illustrations, distribution, specimens examined, and comments for these three species. Furthermore, we place Poa apiculata in Poa subsect. Tovarochloa comb. & stat. nov.
While reviewing Peruvian specimens of Poa , Robert J. Soreng (RJS) found a peculiar collection by John J. Wurdack ( Wurdack 1145 ) from Departamento Amazonas, Provincia Chachapoyas located on the summit of Puma-urcu that is similar to Poa scabrivaginata Tovar and Festuca reclinata but diff ered from the forgoing, and all other Poa species, in having auriculate collars. We describe this as a new species of Poa, but do not include it as a member of P. subsect. Aphanelytrum .
For leaf anatomy, 5 mm long leaf blades were taken from dried herbarium specimens, rehydrated in boiling water, and fi xed in FAA for 24 hours. Th ey were transferred to 70% ethanol, followed by a water rinse and treated for three hours in 50% hydrofl uoric acid (Martens & Uhl 1980). After being neutralized and washed in water the specimens were dehydrated in 2,2-dimethoxypropane (Postek and Tucker 1976) and embedded in Polyfi n (Polysciences, Inc.) paraffi n wax. Transverse serial sections were made at 4 μm, stained with buff ered Toluidine Blue O (Sakai 1973) and mounted in Lipshaw's synthetic mounting resin. Photomicrographic images were captured using a Zeiss Standard 16WL compound microscope equipped with a Retiga 1300i digital camera using ImagePro (MediaCybernetics). Diagnosis. Poa subsect. Aphanelytrum diff ers from most species of Poa in having stooling perennials with decumbent to spreading culm bases that continuously branch and often root at low to mid-culm nodes, glabrous spikelets with long rachillas 1.2-4.2 mm long, short glumes less than ½ the length of the fl orets, and lemmas with bifi d apices that are mucronate to short-awned.

Key to the species of Poa subsection Aphanelytrum
Leaf anatomy. Th e transverse section leaf anatomy of Poa hitchcockiana is C 3 , XyMS+ with non-radiate, spongy chlorenchyma, without adaxial palisade cells. Th ere is a single primary vascular bundle associated with the midrib and a sclerenchyma girder 2 or 3-cells thick on the abaxial surface (Fig. 2D). Lateral primary vascular bundles are widely spaced and also have a few abaxial sclerenchyma cells.
Phenology. Flowering year round [?], although no collections made in February, May, and September.
Distribution. Poa hitchcockiana is found along the paramo or moist jalca vegetation between 2000-4025 m of the Cordillera de los Andes in Colombia, Ecuador, Bolivia, and Peru.
Conservation status. Since the species is widespread it is of least concern (IUCN 2010). However, the typical size of populations is undocumented and it has been noted by the authors that the grass is sought after by grazers since it is often found growing among the protection of perennial shrubs.
Etymology. Since the epithets procumbens and decumbens are blocked in Poa by the earlier P. procumbens Curtis and P. decumbens (L.) Scop., we provide a new name commemorating the "father of American agrostology," Albert Spear Hitchcock (1865Hitchcock ( -1935.
Phenology. Flowering in July. Distribution. Poa reclinata is known only from the type locality, the paramo of the Colombian Cordillera Oriental, Dept. Santander (Stančík and Peterson 2007).
Conservation status. Th e species is rare and its conservation status is data deficient (IUCN 2010).
Etymology. Th e specifi c epithet is probably in reference to the decumbent, spreading or prostrate culms, a frequent characteristic of the species in this subsection of Poa .

Poa sanchez-vegae
Leaf anatomy. Th e transverse section leaf anatomy of Poa sanchez-vegae is C 3 , XyMS+ with non-radiate, spongy chlorenchyma, without adaxial palisade cells ( Fig.  2A-C). Th ere are bulliform cells on the adaxial surface on either side of the midveins primary vascular bundle without additional sclerenchyma (Fig. 2B). However, there are a few abaxial sclerenchyma cells associated with the lateral primary vascular bundles (Fig. 2C).
Phenology. Flowering in March. Distribution. Poa sánchez-vegae is known only from the type locality near the western highlands of the Cajamarca Valley and is found on rocky sites associated with jalca vegetation (humid alpine grass ecosystems) at 3300 m (Sánchez- Vega et al. 2007).
Conservation status. Poa sanchez-vegae is rare and the conservation status is data defi cient (IUCN 2010). However, the authors unsuccessfully searched for additional material of this species at the type locality on 26 Mar 2008, accompanied by two of the original collectors, Isidoro Sánchez-Vega and Juan Montoya. Th e site had been turned into a pine plantation.
Etymology. Since the existing specifi c epithet was occupied in Poa we provide a new name commemorating Isidoro Sánchez Vega, a renowned Peruvian Botanist.
Comments. Based on morphological characters, Isidoro Sánchez-Vega in consultation with Simon Laegaard, fi rst identifi ed the type collection of P. sanchesz-vegae as an unknown species of Aphanelytrum . In Sánchez Vega et al. (2007), we described this taxon as a new Aphanelytrum, and mention that Festuca reclinata superfi cially resembled the genus. In addition, P. sanchez-vegae aligned near or on an unusually long branch within Poa in preliminary cpDNA and ITS sequence analyses ). Gillespie et al. (2008) included three accessions of Poa hitchockiana (≡ Aphanelytrum procumbens ) that formed a clade sister to P. sanchez-vegae (≡ A. peruvianum ) which together was sister to two accessions of P. apiculata (≡ Tovarochloa peruviana ). Th ese results clearly support our classifi cation of P. sanchez-vegae and P. hitchcockiana as members of P. subsect. Aphanelytrum . Diagnosis. Poa auriculata diff ers from Poa scabrivaginata Tovar in having 4-6-fl owered spikelets, a glabrous callus, glumes 2-3 mm long, and lemmas 2.5-3.8 mm long.
Phenology. Flowering in June and July. Distribution. Poa auriculata is known only from the type locality in Cordillera de los Andes of Peru near Chachapoyas between 3100-3200 m growing on a dry cliff face.
Conservation status. Th e species is rare, but its conservation status is data deficient (IUCN 2010).
Etymology. Th e specifi c epithet refers to the triangular auricles that are found on the summit of the sheaths, a feature that is unique among species of Poa .
Comments. Initially RJS considered Poa auriculata to be related to species in P. subsect. Aphanelytrum . We do not place the new species in P. subsect. Aphanelytrum because the spikelets have short rachillas and are 4-6-fl owered, the habit is annual to short-lived perennials with erect culms, and the lemmas are unawned without mucros. However, aside from the auricles, P. auriculata is morphologically consistent with the 300 or so species that reside within P. subg. Poa supersect. Homalopoa . We hope to include a sample of this species in upcoming molecular analyses.