Friday, February 23, 2018

[Botany • 2018] Rediscovery of Thismia neptunis (Thismiaceae) After 151 Years in the Gunung Matang massif, Borneo

Thismia neptunis Beccari

in Sochor, Egertová, Hroneš & Dančák, 2018. 

Thismia neptunis, as many of its congeners, is a poorly understood species that has only been known from the type collection and its limited original description. In January 2017 it was rediscovered in the type area in the Gunung Matang massif, western Sarawak, Borneo, Malaysia. The paper provides the amended description and drawings of the species, very first available photographs and short notes on taxonomy and historical context of Beccari’s work on Thismia

Key words: Brunonithismia, Burmanniaceae, fairy lanterns, Kubah, Monte Mattán, Sarawak

FIGURE 3. Thismia neptunis: flowering plants (A, B), bud (C), detail of flower (D), section of floral tube and outer view of connective tube (E), detail of inner perianth lobe (F), stigma (G), lateral appendage (H).

Taxonomic treatment 
Thismia neptunis Beccari (1878: 251)

 Type:—MALAYSIA. Ragiato di Sarawak, Mattang. April 1866. O. Beccari p.b. 1508 (holotype FI-B 013453!)

Habitat and ecology:—The only known locality is in primary lowland mixed dipterocarp forest on a river alluvium. Thismia species are generally accompanied by other mycoheterotrophic plants; in this case it was Sciaphila cf. alba Tsukaya & Suetsugu (2015: 284). Albeit pollination ecology was not studied, ca. seven flies of family Sciaridae (Diptera) and one individual of family Braconidae (Hymenoptera) were observed being stuck on inner perianth lobes of the two flowers (Fig. 3A, D, E, F). Although the braconid was probably only a coincidental victim, the flies may represent potential pollinators, as several dipteran taxa have been reported as visitors and probable pollinators of fairy lanterns (Li & Bi 2013, Mar & Saunders 2015). Nevertheless, why had they been attracted to and finally trapped on the perianth lobes surface can only be speculated. Tepals are apparently hydrophilic (possibly as a mean of maintaining turgor in the long thin appendages) as indicated by a number of rain drops persisting on them long after the rain. But they do not appear to be sticky and no other particles tended to be trapped on them either in the field or during our manipulation. Therefore, the insects seem to have been attracted by smell (or other signals) of the flowers and accidentally drowned on the wet surface of perianth lobes.

Distribution:—The species is known from a restricted area in western Sarawak, Borneo, Malaysia. Beccari (1878) described the locality simply as “Monte Mattán” or “Mattang”, which is an area now generally known as Matang massif which Kubah National Park is part of it. The present locality is placed at the park’s western border and may be identical or close to that of Beccari.

Taxonomic affinities:—Having free perianth lobes of unequal length and shape, T. neptunis belongs to section Thismia (Euthismia Schlechter, 1921: 34), subsection Brunonithismia Jonker (1938: 242). This group comprises nine species (Kumar et al. 2017, Suetsugu et al. 2018) of very diverse morphology as for symmetry of perianth, modification of perianth lobes and structure of connectives. Half of the species are, nevertheless, only poorly documented. Thismia neptunis is unique among other fairy lanterns in the very complex three-segmental structure of inner perianth lobes that are terminated by long filiform appendage pointing vertically upwards. This striking morphology led Schlechter to creation of monotypic section Sarawakia Schlechter (1921: 35) within his system of Thismia (Schlechter 1921). However, his approach has not been generally accepted (Jonker 1938, Kumar et al. 2017). 

Beccari was also well aware of morphological uniqueness of T. neptunis. In the protologue (Beccari 1878), he stated that T. neptunis seems to have connectives similar to T. brunonis Griffith (1844: 221). However, T. brunonis have apical part of the connective covered by numerous short teeth (Griffith 1845) while T. neptunis have only three rather long appendages. Nevertheless, Beccari himself was not absolutely sure about the character of connectives as he studied only two pressed and dried plants. In having whitish perianth tube with 12 orange streaks T. neptunis superficially resembles T. javanica Smith (1910: 32) and T. arachnites Ridley (1905: 197). Both of them, nevertheless, differ in having short rounded outer perianth lobes and simpler spreading inner perianth lobes, and the latter species also in having “numerous short teeth” at the apical end of connectives. Connectives of T. javanica, although similar at a first glance, differ from those of T. neptunis in colour (white vs. orange, respectively) and three short teeth at the apex, each bearing 1–2 long hairs of similar length (vs. three unequal filiform appendages in T. neptunis). Thismia neptunis is so far the only known member of subsection Brunonithismia occurring in Borneo.

Michal Sochor, Zuzana Egertová, Michal Hroneš and Martin Dančák. 2018. Rediscovery of Thismia neptunis (Thismiaceae) After 151 Years. Phytotaxa. 340(1); 71–78.  DOI: 10.11646/phytotaxa.340.1.5