The Thepparatia Page

Thepparatia scandens (Roxb. ex G.Don) Phuph.

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Thepparatia Phuph. is a recently described (2006) monotypic genus, name from a collection from dry evergreen forest in Tak province in northwestern Thailand. The genus is named to honour the Thai royal Her Royal Highness Princess Maha Chakri Sirindhorn. (Thepparat is her royal title.) [1] The type species is Thepparatia thailandica Phuph., but this has been subsequently identified as being conspecific with Hibiscus scandens of Burma, Bangladesh and India. [21]

This genus was described as related to Thespesia but differing in being a woody climber, in lacking foliar (and epicalyx) nectaries, in possessing articulate pedicels, and in having a inflorescence composed of a terminal raceme of more than 10 flowers. [1] However a molecular study of Thespesia found Thepparatia to be nested in Hibiscus. [3]

Description

The single known species is Thepparatia scandens (Roxb. ex G.Don) Phuph. This is a woody climber with stems up to 20m long. The leaves are spirally arranged, and crowded towards the ends of the branches. They are broadly ovate, 7-12×8-12cm in size, chartaceous, shallowly to moderately 3-lobed, with a cordate base, acuminate apex, and an irregular crenate-serrate margin. Glands are present on the upper surface, and also on the midrib and other veins. The upper surface is glabrous; the lower surface minutely stellate-pubescent with some large stellate hairs. The petioles are 5-10cm long, with a minutely stellate-puberulous indumentum. The stipules are caducous, filiform, and 4-6mm long.

The flowers are borne in drooping racemose inflorescences situated at the end of branches. These are up to 20 cm long, with a stellate-tomentose indumentum. The flowers are pedicellate, the pedicels being 1.5-1.8 cm long, with an articulation about 0.5 cm below the epicalyx. The persisent epicalyx is composed of 5-7 oblong to elliptic bracteoles, 7-10×3-5mm in dimension, which are reddish-green in colour, fused at the base, and stellate-tomentose on both surfaces. The calyx is 10-14mm long. It is composed of 5 green sepals, which are fused for about half their length. The free portions are ovate, 5-8×4-5mm in size, with an acute apex, a medial nerve, and a stellate-tomentose indumentum on both surfaces. The corolla is described as yellow, with a large dark-red centre. (Photographs show the outermost parts of the petals as near-white, but this might be due saturation of the images.) It is campanulate. The petals number 5. They measure 3-3.5×1.5-2cm in size, and are adnate to the base of the staminal tube, and obovate. The apex is reflexed. The outside surface is stellate-puberulous, with longitudinal lines; the inside surface glabrous.

The staminal column is 1.5-2cm long, with an unequally 5-toothed apex, and is densely antheriferous throughout its length. The filaments are about 1mm long, frequently occurring in pairs. The anthers are yellow and horseshoe-shaped. The pollen is echinate.

The ovary is ovoid, densely pubescent, and composed of 5 cells, each containing 12 ovules. The pistil is described as being shorter than the staminal column, with and undivided style, and with a small, non-sulcate, stigma, constrasting with the state in Thespesia, where the pistil is longer than the staminal column, with a clavate, 5-sulcate, papilose, stigma. However I prefer a different interpretation - that the flowers are protandrous (i.e. that the stamens mature before the pistil), as in many malvaceous plants, and that the mature pistil exceeds the length of staminal column. Under this interpretation the nature of the mature stigma is unknown. (It is possible instead that the staminal column is shed to expose the pistil, but this doesn't seem consistent with the adnation of petals and staminal column.)

The fruits are densely stellate-hispid oblong mucronate capsules. The seeds are covered with cotton-like hairs. [4]

Distribution

Thepparatia scandens is recorded from northwest Thailand [1], the eastern Himalayas [5], the Chittagong Hills of Bangladesh [6], the Andaman Islands [7] and south eastern Burma (Tenasserim) [4].

Taxonomic musings

There are two other scandent species of Hibiscus from the same general area, and sharing other features with Thepparatia scandens - Hibiscus fragrans Roxb. and Hibiscus austroyunnanensis C.Y.Wu & K.M.Feng. I am entertaining the hypothesis that these form a natural group, and should be be included in the same genus or infrageneric taxon.

As Thepparatia has been found to be nested within Hibiscus whether or not the genus should be continued to be recognised depends on a number of factors. The first is how the paraphyly of Hibiscus is to be handled; if the proposal to extend Hibiscus to include most of the nested taxa (and exclude a group of Malagasy species) is adopted then Thepparatia should be synonymised with Hibiscus.

The second is the subjective decision as to whether it is sufficiently morphology distinctive to be separated from its sister group within Hibiscus.

The third is its position within Hibiscus, and the implications as to how much further Hibiscus would have to be dissected to both continue to recognise Thepparatia and maintain the principle of monophyly. The published cladogram does not closely resolve its position; it is closer to the /Trionum clade than to Urena, and presumably the broader /Phylloglandula clade. [3] That could place it in the /Euhibiscus clade, or the /Trionum clade, or as an independent lineage.

The fourth factor is a nomenclatural one; if Thepparatia is extended to include .

References

  1. Phuphathanaphong, L., Thepparatia (Malvaceae), a new genus from Thailand, Thai For. Bull. (Bot.) 34: 195-200 (2006)
  2. Plants of the World Online
  3. F. Areces-Berazain & J. D. Ackerman, Phylogenetics, delimitation and historical biogeography of the pantropical tree genus Thespesia (Malvaceae, Gossypieae), Bot. J. Linn. Soc. 181(2): 171?198 (2016)
  4. Kurz, Forest Flora of British Burma 1: 127 (1887)
  5. Masters, Maxwell T. in Hooker, J.D., The Flora of British India 1: 1: 337 (1875)
  6. Roxburgh, Flora Indica 3: 200 (1832)
  7. C. Sudhakar Reddy, Flora of the North Andaman Islands (2013)

References

  1. Flora of Thailand 14(2): 329 (2019)

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