Saturday, September 16, 2017

[Botany • 2017] Thismia nigricoronata • A New Species of Burmanniaceae (Thismieae, Dioscoreales) from Vang Vieng, Vientiane Province, Laos, and A Key to Subgeneric Classification


Thismia nigricoronata  Kumar & S.W.Gale


Abstract

Thismia nigricoronata is described as a new species in family Burmanniaceae. Both morphological and phylogenetic analyses indicate that this new Lao endemic is allied to T. taiwanensis in section Glaziocharis, and it can be differentiated on the basis of its longer vestigial stem leaves, reflexed free outer perianth lobes and ornamented, vibrantly coloured outer surface of the perianth tube. The infrageneric taxonomy of Thismia is reviewed, the genera Geomitra and Scaphiophora are officially reduced to sectional status in Thismia, and all species are enumerated in systematic order. A key to all currently accepted subgenera, sections and subsections is presented to facilitate further examination of their phylogenetic integrity in light of apparent conflict between the traditional morphology-based system and the emerging DNA-based classification.

Keywords: achlorophyllous plants, Dioscoreaceae, holomycoheterotrophs, Laotian flora, Thismiaceae, Monocots

FIGURE 4. Thismia nigricoronata  Kumar & S.W.Gale. 
A. Plant in habitat. B. Habit. C. Close-up of the crown. D. Whole plant showing the structure of the crown. E. Whole plant showing the structure of the annulus. F. Transverse section of the perianth tube. G. Dorsal view of the crown. H. Stamens showing the anther locules. I. Stamens showing the connectives and staminal tube.


Thismia nigricoronata Kumar & S.W.Gale, sp. nov. 

Thismia nigricoronata is morphologically similar to Thismia taiwanensis but can be differentiated on the basis of its longer vestigial stem leaves (more than 6 mm long in the former versus less than 6 mm in the latter); its reflexed free outer perianth lobes (versus erect and projecting upwards in the latter); the ornamented outer surface of its perianth tube, which is verrucose below and papillose above (versus smooth and glabrous in the latter); and its vibrantly coloured perianth tube (versus translucent white in the latter).

 Habitat:— Thismia nigricoronata was discovered on a steep slope of a limestone mountain, growing among leaf litter in clayey soils under a dense evergreen canopy.

  Etymology:— The species epithet refers to the blackcrown-like structure formed above the annulus by the fusion of the three inner perianth lobes. Hence the taxon may informally be referred to as ‘the black-crowned thismia’.


 Pankaj Kumar, Stephan W. Gale, Ji-Hong Li, Somsanith Bouamanivong and Gunter A. Fischer. 2017. Thismia nigricoronata, A New Species of Burmanniaceae (Thismieae, Dioscoreales) from Vang Vieng, Vientiane Province, Laos, and A Key to Subgeneric Classification.    Phytotaxa. 319(3); 225–240.  DOI:  10.11646/phytotaxa.319.3.2


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