Nepenthes pudica Dancak & Majesky, 2022

Dancak, Martin, Majesky, Ľubos, Cermak, Vaclav, Golos, Michal R., Plachno, Bartosz J. & Tjiasmanto, Wewin, 2022, First record of functional underground traps in a pitcher plant: Nepenthes pudica (Nepenthaceae), a new species from North Kalimantan, Borneo, PhytoKeys 201, pp. 77-97 : 77

Nepenthes pudica Dancak & Majesky sp. nov.

Figs 1 , 2 , 3 , 4 , 5

Diagnosis.

Nepenthes pudica differs from N. hispida Beck in producing short basal underground (vs. aboveground) shoots; ± glabrous (vs. hairy) stems; petiolate (vs. sessile) climbing shoot leaves with auriculate, shortly decurrent (vs. decurrent-amplexicaul) bases; rare (vs. common) upper pitchers; red (vs. green or red blotched) lower pitchers; ± glabrous (vs. hairy) mature pitchers; ventricose (vs. ovoid-ellipsoid) lower pitchers; infundibular (vs. subcylindrical, tapering) upper half of the lower pitcher; 3-5.5 cm (vs. 1.5-3 cm) wide lower pitchers; male flowers in pairs (vs. single or rarely in pairs) and androphore c. 4 mm (vs. 1.5-2 mm) long.

Type.

Indonesia. North Kalimantan: Malinau Regency , c. 1110 m a.s.l., 2 February 2012, W. Tjiasmanto, M. Paris & M. Dančák s.n. (BO, holotype BO1985840, isotype BO1985839) .

Description.

Terrestrial climber producing climbing shoot and underground basal shoots. Climbing shoots up to c. 20 m long, stem glabrous, c. 4-6 mm thick, internodes c. 4 cm long. Underground basal shoots short, with reduced, partially or completely achlorophyllous leaves (nanophylls) bearing well-developed lower pitchers, not observed to branch or develop roots. Rosette leaves chartaceous, subsessile to shortly petiolate, oblanceolate, up to 16 cm long, up to 4 cm wide, apex subobtuse or acute to acuminate, base auriculate, shortly decurrent, glabrous on both sides but densely hairy with short brown hairs on the margins, tendril up to 16 cm long, uncoiled. Leaves of climbing shoots coriaceous, shortly petiolate, oblanceolate, up to 20 cm long, up to 4.5 cm wide, with 2-4 inconspicuous longitudinal veins on each side of the midrib, apex acute, base auriculate, shortly decurrent, glabrous on both sides, margins glabrous, tendril coiling. Rosette pitchers produced only briefly on aboveground rosettes, up to 9 cm high, up to 3 cm wide, thin-chartaceous, subcylindrical to ovoid in the lower part. Lower pitchers produced exclusivel on underground basal shoots, 7-11 cm high, 3-5.5 cm wide, thin-coriaceous, becoming thicker-walled and markedly sturdier when produced at depth, arising abruptly from the uncoiled tendril, ventricose, broadly ovoid to globose in the lower half, infundibular above, clearly widening towards the mouth; eglandular zone of the inner surfaces extending from the mouth almost to the middle of the pitcher; inner surface near the mouth white, conspicuously red blotched, outer surface red-purple, faintly blotched, occasionally entirely off-white when produced at depth; two fringed wings running from the bottom of the pitcher to the mouth at the front; mouth round, rising at the rear into a short neck; peristome cylindrical in section, up to 2 mm wide, inner surface with distinct teeth up to 0.8 mm long, ribs up to 0.5 mm apart, up to 0.2 mm wide; lid broadly ovate, c. 20-30 mm long, c. 20 mm wide, with short spur; large, craterlike nectar glands ± elliptic in outline, up to 0.35 mm long, scattered densely in the middle of the lower surface. Upper pitchers rarely produced, up to 9 cm high, up to 2 cm wide, thin-coriaceous, arising gradually from the tendril, narrowly infundibular at the base, subcylindrical above; eglandular zone of the inner surfaces covering upper 1/3 of the pitcher; outer surface green, inner surface near the mouth yellowish; two fringed wings running from the middle of the pitcher to the mouth at the front; mouth round, with or without very short neck; peristome cylindrical, up to 1.5 mm wide, inner surface with very short teeth, ribs up to 0.25 mm apart, c. 0.1 mm wide; lid broadly ovate, 11-16 mm long, 9-13 mm wide, with curved spur; craterlike nectar glands as in lower pitchers, up to 0.3 mm long. Male inflorescence a raceme, peduncle c. 14 cm, rachis c. 13 cm, partial peduncles 2-flowered, bracts absent, pedicels 4-7 mm long, tepals elliptic, up to 6 by 3 mm; androphore c. 4 mm long, anther head 2.5 by 1.5 mm. Female inflorescence unknown. Infructescence racemose. Fruit a fusiform capsule, reddish brown at maturity, conspicuously glossy, valves of fruits c. 45 by 4 mm. Seeds 20-25 mm long.

Habitat and ecology.

The species occurs on ridgetops over sandstone rocks in lower montane rainforest. The known elevational range is 1100-1300 m a.s.l. The plants frequently grow near trees whose branched roots form cavities covered with a moss layer. Lower pitchers are then copiously produced inside these cavities. If no cavities are available, the pitchers are produced directly in soil, deep litter or under moss cushions. At some sites, Nepenthes tentaculata Hook.f. and N. stenophylla Mast. grew sympatrically with N. pudica , while a species from the N. fusca species complex was spotted growing epiphytically in at least one locality.

The subterranean growth habit of Nepenthes pudica was consistently observed across the five studied sites but was not shared by the sympatric Nepenthes species, demonstrating that it was not simply the result of unusual local conditions. The underground shoots of N. pudica had no obstacles preventing them from growing upwards, suggesting that they are not negatively gravitropic as is typical of stems. Neither did they show signs of growing towards light, even when concealed only under a soft moss cushion or already slightly chlorophyllous (Fig. 2B ). Based on this and their generally lateral character, it might be supposed that they are negatively phototropic rather than positively gravitropic.

Distribution.

The species is known only from a few adjoining localities in the western part of the Mentarang Hulu district of North Kalimantan, Indonesia. The exact locations have been withheld in order to prevent poaching by unscrupulous commercial collectors.

Etymology.

The specific epithet pudica (bashful, shy), is a feminine adjective and alludes to the fact that lower pitchers remain concealed from direct view.

Conservation status.

Nepenthes pudica is endemic to Borneo. It is known from five closely situated sites, which represent a single location ( IUCN 2022). Both the extent of occurrence (EOO) and minimal area of occupancy (AOO) of N. pudica are estimated to be less than 4 km2. There is uncertainty as to whether the species occurs within Kayan Mentarang National Park, as its borders were not marked in the field at the time of discovery. However, the available maps suggest all the sites are actually located outside the national park, thus legally unprotected. Due to its restricted distribution, small population size and possible habitat loss, the species qualifies to be assigned preliminary conservation status as critically endangered (CR), based on criteria B1 ab(iii) and D of the IUCN Red List categories and criteria ( IUCN 2012).

Prey composition and infauna.

We found 1785 invertebrate individuals belonging to 40 different taxa (Tables 2 , 3 ) in suspensions sampled from five underground pitchers (found in a tree-root cavity) and one aerial rosette pitcher (growing 2 metres above the soil surface and arising from an offshoot of a fallen climbing stem). Necromass of the prey consisted of sclerites of highly digested invertebrates. It contained mainly litter- and soil-inhabiting species as well as a large amount of plant detritus. Among soil- and litter-inhabiting species we observed mites (mostly from the family Oribatidae ), leaf litter-inhabiting beetles (families Scydmaenidae , Pselaphidae , Liodidae , Carabidae ) and a single ant of the genus Anochetus (subfamily Ponerinae ). These taxa are mostly mycophagous, detritophagous, or predators. However, the main and the essential prey component was a species of ant from the subfamily Myrmicinae , probably a species of the genus Crematogaster , which is closely associated with Nepenthes ( Bonhomme et al. 2011). A number of individuals of an ant from the genus Polyrhachis were found in the aboveground rosette pitcher in contrast with their rare occurrence in underground traps.

Surprisingly, we found relatively numerous infauna, especially larvae of mosquitoes, nematodes and annelids in both aboveground and underground pitchers (Table 3 ). We identified three species of mosquitoes from two genera, Uranotaenia and Culex . Identified nematodes belong to seven families: Aphelenchoididae , Cephalobidae , Diplogastridae , Panagrolaimidae , Plectidae , Rhabditidae (dauer larvae) and Wilsonematidae . The most abundant were members of families Rhabditidae and Diplogastridae detected in the aboveground trap, which were previously recorded from the pitcher fluid of Nepenthes mirabilis (Lour.) Druce ( Bert et al. 2011). In underground traps, nematodes were rare and in different compositions compared to the aboveground trap. The most abundant were members of the families Cephalobidae ( Heterocephalobus ) and Panagrolaimidae ( Panagrolaimus ). One of the most interesting inquilines found in the underground pitchers was a new species of annelid worm, Pristina armata (family Naididae ), described previously by Schenková and Čermák (2013).

Selected specimens examined.

See Suppl. material 1.

Figures

Figure 1. Nepenthes pudica A juvenile rosette pitcher B upper pitchers (4 on the right; each from a different plant), intermediate pitcher (1 on the left) C habitat with mature plant D habitat with lower pitchers excavated from the soil. Photographs by M. Dancak.

Figure 2. Nepenthes pudica A detail of lower pitchers excavated from the soil B lower pitchers in a cavity under tree roots-note greening of phyllodia formed in presence of low light C lower pitchers revealed under a moss mat D lower pitchers extracted from a cavity-note achlorophyllous shoot and reduced phyllodia formed in total darkness. Photographs by M. Dancak.

Figure 3. Nepenthes pudica A male flowers B male plant with inflorescence C infructescence D female plant with infructescence. Photographs by M. Dancak.

Figure 4. Nepenthes pudica, SEM images of lower pitcher A outer wall with outer margin of peristome B detail of trichome on the outer wall C inner wall and inner margin of peristome showing eglandular zone covered with lunate cells and peristome teeth with peristomal glands D inner wall showing glandular zone with digestive glands. SEMs by B. J. Plachno.

Figure 5. Nepenthes pudica A habit B lower pitcher C infructescence D male inflorescence E detail of climbing stem with a leaf. Drawn by Katerina Janosikova.