Saturday, November 14, 2015

[Botany • 2014] Thismia hexagona var. grandiflora • A New Variety of Thismia hexagona (Thismiaceae) from Sabah, Borneo, Malaysia


Fig. 1. Thismia hexagona var. grandiflora Tsukaya, M. Suleiman & H. Okada var. nov. in its native habitat (type locality). A, Flowers of T. h. var. grandiflora. B, Gross morphology of T. h. var. grandiflora (scale = 1 cm).

Thismia hexagona Dančák, Hroneš, Koblová et Sochor was recently reported from Brunei Darussalam. It is characterized by its unique yellow and brown coloration and sharply hexagonal flower annulus. Here, we also report its discovery during a botanical expedition in the Maliau Basin Conservation Area, Sabah, Borneo, Malaysia. The Malaysian individuals differ from the original description of T. hexagona in the opening angle and size of the perianth lobes. We therefore propose it as a new variety, Thexagona var. grandiflora Tsukaya, M. Suleiman & H. Okada var. nov. Detailed morphological characters are provided. 

Key words: Borneo, mycoheterotroph, new locality, Sabah, Thismia hexagona, Thismiaceae

Taxonomic treatment
Thismia hexagona var. grandiflora Tsukaya, M.Suleiman & H. Okada, var. nov. —Fig. 1.

Thismia hexagona var. grandiflora differs from Thexagona var. hexagona in having much longer perianth lobes that open perpendicularly to the floral axis.

Typus. MALAYSIA, Maliau Basin Conservation Area, Sabah: 04°44'29"N, 116°57'55"E, 235 m alt., from the Studies Center to Seraya Camp, Maliau Basin Conservation Area, 15 Aug. 2013, H. Tsukaya, M. Suleiman & H. Okada KKT-1 (holo-BORH, iso-TI, KYO; part of specimen preserved in 50% ethanol, at all three herbaria).


Fig. 1. Thismia hexagona var. grandiflora Tsukaya, M. Suleiman & H. Okada var. nov. in its native habitat (type locality).
 A, Flowers of Th. var. grandifloraB, Gross morphology of Th. var. grandiflora (scale = 1 cm).

The genus Thismia Griff. (Thismiaceae) comprises more than 45 mycoheterotrophic species (Jonker 1948; Merckx 2008; Merckx et al. 2013), including several species described within the past decade, such as T. mullarensis from Central Kalimantan (Tsukaya & Okada 2005), T. betung-kerihunensis from West Kalimantan (Tsukaya & Okada 2012a), and T. hexagona from Brunei (Dančák et al. 2013). The majority of these species appear to have been collected only once or a few times. Since mycoheterotrophs are highly dependent on the activities of both the fungi and the trees that sustain them, the richness of the mycoheterotroph flora is a good indicator of the floristic richness of the forests in which they occur (Merckx et al. 2013). In other words, mycoheterotrophs are easily affected by ecosystem destruction.

To conserve the biodiversity of tropical forests, we need additional information on the distribution of such vulnerable mycoheterotrophs. In our floristic studies in the Kalimantan area of Borneo we found one new genus, several new species, and a new variety of mycoheterotrophs (Tsukaya & Okada 2005, 2012a, 2012b, 2013a, 2013b, Tsukaya et al. 2011). Because Kalimantan has a rich diversity of mycoheterotrophs, we compared the mycoheterotroph floras of Kalimantan and Sabah, Borneo, starting with a botanical expedition in Maliau Basin Conservation Area, Sabah, with permission from the Maliau Basin Management Committee (YS/MBMC/2013/50) and Sabah Biodiversity Council [access license JKM/MBS.1000-2/2(152)]. We chose this area because Dr. Tim Utteridge, of the Royal Botanic Gardens, Kew, kindly showed one of us (HT) photographs of Thismia that he took in the conservation area. We suspected the photos to represent a new species of Thismia, based on other photos of Thismia taken by a professional photographer in Sabah, until the report of a new species T. hexagona, which looks similar, was published by Dančák et al. (2013). During our survey, we found three populations of T. hexagona flowering in the Maliau Basin Conservation Area. This is the first report of T. hexagona from Sabah. Because our collections have much longer perianth lobes than the typical variety, we describe them as T. hexagona var. grandiflora Tsukaya, M. Suleiman et H. Okada.

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Hirokazu Tsukaya, Monica Suleiman and Hiroshi Okada. 2014. A New Variety of Thismia hexagona Dančák, Hroneš, Koblová et Sochor (Thismiaceae) from Sabah, Borneo, Malaysia. Acta Phytotax. Geobot. 65(3): 141–145. http://ci.nii.ac.jp/naid/110009922438

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