Re-evaluation of the taxonomic status ofHackelochloa(Poaceae) based on anatomical and phenetic analyses

Abstract

Hackelochloa is a pantropical genus of plant in the Poaceae, in which only two species have been included, H. granularis and H. porifera. Despite several morphological differences, notably the more prominent sculpturing of the lower glume and the larger dimensions of several quantitative traits, H. porifera has been reduced to the synonymy of H. granularis. Moreover, the status of the genus itself has been questioned, with a regional revision of the genus proposing inclusion of its members in the genus Mnesithea. In the present study, we investigated a range of morphological and anatomical attributes to assess critically the generic delimitation between Hackelochloa and Mnesithea. In clustering analysis, H. granularis, H. porifera and Mnesithea species were clearly resolved as three distinct groups with an R-value of 0.98114. Likewise, three clusters representing these taxonomic units were revealed using principal component analysis (PCA), with the first two principal components highlighting key qualitative and quantitative characters. Scanning electron microscopy was used to reveal different patterns of sculpturing on the lower glumes in the two putative species and the ecological significance of these differences is inferred. The outline of leaf transverse sections, presence of parenchymatous tissue in the midrib region, number of adjacent bundles and number of chlorenchyma layers in the culm were also found to be diagnostic anatomical characters. This study supports the recognition of H. porifera as distinct from H. granularis and provides evidence that the genus Hackelochloa should be maintained.

A worldwide phylogenetic classification of the Poaceae (Gramineae) II: An update and a comparison of two 2015 classifications

“…Accordingly, Dimeriinae is placed in Ischaeminae, Sorghinae in Saccharinae, and Anthistiriinae in Andropogoninae. Gosavi et al (2016) and Arthan et al (2016) offer new insights in Rottboelliinae, and we now accept Hackelochloa (as did Kellogg). Kellogg (2015, p. 300) mentioned an unpublished DNA study where Coelorachis is placed in Rottboellia rather than Mnesithea as proposed by Veldkamp et al (1986); and we now follow that here.…”

Phylogenomics enables biogeographic analysis and a new subtribal classification of Andropogoneae (Poaceae—Panicoideae)

“…Generic limits in the Rottboelliinae and Ratzeburgiinae are famously complex, with morphological characters intergrading between species and genera; many species have names in several genera. Veldkamp et al (1986) described the group as “a botanical black hole (…) the smaller and larger genera around the complex spiral down into making its mass even greater and its circumference even more difficult to envisage.” His solution was to place species formerly assigned to Coelorachis Brongn., Hackelochloa, Heteropholis, Ratzeburgia , and Rottboellia in Mnesithea , although this suggestion has not been widely followed (see, e.g., Davidse et al, 1994; Barkworth et al, 2003; Arthan et al, 2016). All members of this group have unawned spikelets, with the sessile one generally sunken into the inflorescence axis, the glumes indurate, the pedicellate spikelet often reduced or lacking, and the pedicel sometimes entirely fused with the inflorescence axis (Clayton, 1973).…”

Contribution to the flora of Asian and European countries: new national and regional vascular plant records, 7

“…Soreng et al (2015) placed its two members in the related genus Mnesithea Kunth, and Hackelochloa porifera has subsequently been treated as a synonym of Mnesithea granularis (L.) de Koning and Sosef. Recently, Arthan et al (2016) supported the recognition of Hackelochloa porifera as distinct from Hackelochloa granularis and provided evidence that the genus Hackelochloa should be maintained. Hackelochloa granularis differs from Hackelochloa porifera in spikelet morphology.…”