Parahyparrhenia A. Camus (1950: 404)

Landge, Shahid Nawaz & Shinde, Rajendra D., 2022, A taxonomic revision of the genus Parahyparrhenia (Poaceae: Andropogoneae) in India and review of African and Thai species, Phytotaxa 541 (3), pp. 247-260 : 248-249

Parahyparrhenia A. Camus (1950: 404) .

Type species:— Parahyparrhenia jaegeriana A. Camus (1950: 404) .

Type:— MALI [French Soudan]. French West Africa , Massif de Kita, 16 February 1950, Jaeger 17 (holotype K barcode K000280143 [digital image!], available athttp://specimens.kew.org/herbarium/ K000280143 .

Annual or perennial, caespitose, erect or geniculately ascending herbs, 20–160 cm high; leaves 6.0–45× 0.1–0.6 cm, glabrous or pubescent, glaucous or not, margin scabrous or smooth, blades drooping, reflexed or erecto-patent; ligule usually membranous rarely ciliate; Inflorescence racemes, usually binate, sometimes solitary or in scanty false spatheate panicles; raceme bases sub-equal to unequal, not deflexed, tip oblique without any distinct appendage (see Parahyparrhenia annua ); racemes 4–14-awned per pair; homogamous spikelets at the base of raceme well developed, 1.0–7.0 pairs, strictly staminate or barren, reduced to joints or vestigial scale or completely absent. Pedicel and rhachis internode sub-equal, ciliate on both the margins, tips oblique. Sessile spikelets linear, 5.0– 12 mm long: callus obliquely pungent 1.5–4.0 mm slightly outwardly protruded, bearded with white, rufous or purplish hairs; lower glume 3.0–12- nerved, sometimes almost inconspicuously nerved, with a median longitudinal on the back or rarely convex, glabrous, scabrous in the upper part or not distally pilose or glabrous, tip acuminate, acute, bidentate or tridentate; upper glume 1–7-nerved, more often aristate, less often exaristate, tip lobed or not; lower floret barren, reduced to a hyaline epaleate lemma or altogether absent; upper floret strictly hermaphrodite, with or without minute scale-like palea, sometimes conspicuous, hyaline lemma constituting a base of a principal geniculate awn; awn 20–100 mm, issuing from sinus of a bi-lobed fertile lemma, hispidulous or puberulous; stamens 3, anthers 0.5–5.0 mm. Pedicelled spikelets narrowly lanceolate, 5.0– 11 mm long, shorter, sub-equal or longer than the sessile counterparts, variably staminate or barren, never hermaphrodite, aristate or muticous: callus oblong, short or long stipe-like, or completely absent, 0.5–2.0 mm long; lower glume with or without a longitudinal groove; lemma aristate or exaristate.

Etymology:—The genus Parahyparrhenia (para =beside) was erected based on some of its unusual characters, as discussed below, close to Hyparrhenia . The type species has been eponymised after the name of the type collector, Mr. Jaeger.

Note:—According to Camus (1950), Parahyparrhenia “differed from Hyparrhenia in its geminated [bi-nate] pseudo-spikes [spiciform-raceme] which are very rarely isolated [solitary] on top of the reed [culm] and do not usually occur in panicles, the spathe is reduced, sessile spikelets with cutting callus, a little oblique [sharp and pungent], very hairy, sericeous, there is a pair of similar spikelets [homogamous], very reduced, with awns, located at the base of the pseudo-spike [spiciform-raceme], sub-sessile. There are 4–5 pairs of spikelets per raceme. The sessile spikelets are very different in form to the pedicelled spikelets. The pseudo-spikes [spiciform-raceme] are sub-contiguous, with the awns of the fertile spikelets tangling such as in genus ‘ Heteropogon ’, giving the impression of making one single raceme, but the inferior homomorphic spikelets are less developed than the spikelets of other pairs, with awns short and not twisted.” (Translated in English from French script of the protologue by Mr. Carlos Enrique Sánchez Ocharan, Peru, South America)

Distribution:—Native range of the genus is from West Tropical Africa to Sahara and Sudan, Peninsular India, Indo-China ( Thailand); showing highly disjunct distributional pattern.

Flowering & fruiting:—September to January.

Habitats & Ecology:— The genus is known to occupy a narrow distributional range in Africa, India and Thailand. It is fascinating to note that none of the species has an inter-continental distribution—they are only known from their native, specifically-confined and peculiar habitats. Acquisition of peculiar ecological niches such as: ephemeral pools during the rainy season on ironstone outcrops (in Africa); sloping sandstone with some water and seasonally flooded lands (in Thailand); in the crevices of quartzite (Quartz Arenite) rocks and open grassland (in India); making them difficult to locate outside of such specific geographical settings, thus making the genus extremely rare in occurrence and vulnerable too.

Affinities

On the three occasions the generic circumscription of Parahyparrhenia was significantly inflated to receive certain anomalous features, that were earlier not part of the genus, i.e. the convex lower glume of sessile spikelet in P. tridentata ; absence of the homogamous spikelets at the base of a raceme in P. siamensis and a stipe-like callus at the base of a pedicellate spikelet in P. laegaardii . It is interesting to note that all of these species are from Thailand. The above mentioned features are also seen in the marginal genera Hyparrhenia Andersson ex Eugène Fournier (1886: 67) and Elymandra Stapf (1919: 407) . According to Clayton (1966), based on morphology, Parahyparrhenia has affinities with Hyperthelia , Diheteropogon Stapf (1922: 3093) and Elymandra . Because all of these genera have homogamous pair(s) of spikelets present at the base of the raceme. According to Clayton (1969a) and Arthan et al. (2017), Hyparrhenia also have a pair of homogamous spikelets at the base of raceme. Perhaps, in Parahyparrhenia this feature was derived from Hyparrhenia .

In the recent phylogenomic study by Arthan et al. (2017) which evaluated the systematic position of the genus within Andropogoneae , found Andropogon burmanicus Bor (1960: 688), Eulalia contorta Kuntze (1891: 775) and Parahyparrhenia siamensis form a previously unidentified lineage in Andropogoneae with inflorescence characters that appear convergent with those of well-established genera. In their discussion they state: based on overall morphological similarity (as described in, for example, Clayton 1972, Clayton & Renvoize 1986, Watson & Dallwitz 1992, Veldkamp 2003, Soreng et al. 2015), we had expected that P. siamensis would be closely related to Hyparrhenia Andersson ex Eugène Fournier (1886: 67) , instead A. burmanicus and P. siamensis are in a clade with Eulalia contorta that is entirely Southeast Asian, but sister to the widespread genus Eriochrysis Palisot Beauvois (1812: 8) . Perhaps, it is due to a lack of homogamous spikelet at the base of spiciform-raceme that P. siamensis was in a clade with A. burmanicus . However, their study is based on a single species of the genus Parahyparrhenia and the other six species have yet not been assessed on molecular grounds; thus, monophyly of the genus is uncertain.

By the inclusion of anomalous features of the three Thai species into the genus, its circumscription has become somewhat indistinct from allied genera, posing difficulties for generic identification. It seems that any further additions with exceptional features might question generic stability.