Nepenthes zygon Jebb & Cheek, 2014

Cheek, M. & Jebb, M., 2014, Expansion of the Nepenthes alata group (Nepenthaceae), Philippines, and descriptions of three new species, Blumea 59 (2), pp. 144-154 : 151-153

Nepenthes zygon Jebb & Cheek , sp. nov. — Fig. 3

Differs from N. mindanaoensis Sh.Kurata , in having leaf blades narrowly oblong-elliptic (not ovate-lanceolate),petiole with wings patent (not strongly involute, appearing cylindric), basal lid appendage present in upper pitchers, conspicuous, strongly convex or hooked (not inconspicuous or weakly developed). — Type: Cheek 17059 (holotype K; isotypes L, PNH), Philippines, Mindanao Island , Mt Pasian , seed collected in 1997 by R. Cantley , cultivated at Royal Botanic Gardens, Kew as accession 2004-2413, male infl. Sept. 2013 .

Synonymy. Nepenthes alata Blanco var. ecristata sensu Macfarlane (1927) 137 non Macfarl. (1908) 72, quoad Elmer 14248.

Nepenthes alata sensu Danser (1928) 261 non Blanco, quoad Elmer 14248.

Etymology. The epithet zygon , here used as a noun in apposition,derives from the Greek, meaning yoked or coupled, to signify the close linkage with N. mindanaoensis .

Terrestrial climber 2–3 m tall, possibly sometimes rooting on bases of stunted trees in cloud forest. Stem terete, 5.5–9.5 mm diam. Rosette and short stems not well-developed. Climbing stems with internodes (2.8–) 5–12 cm long, axillary buds filiform 5(–7) by 0.9 mm long, inserted 6–9 mm above the axil, indumentum of patent brown ‘dagger hairs’ ( Kurata 2003) 0.2–0.5(–0.8) mm long, very sparse to 20–30 % surface coverage, denser in leaf axils; sessile red depressed-globose glands 0.05 mm diam, scattered throughout. Leaves thinly coriaceous, petiolate. Rosette leaves oblanceolate, 14–18 by 4–4.5 cm. Leaves of climbing stems narrowly oblong-elliptic, 21–24(–30) by 2.8–5.5(–7) cm; apex acute, not peltate; base decurrent to petiole; longitudinal nerves 1–2 pairs, 2–10 mm from the margin, arising from the midrib of the blade, conspicuous above; pennate nerves numerous, patent, conspicuous above; midrib upper surface 20–30 % covered in a mixture of dark brown simple or ‘dagger hairs’ 0.06–1 mm long and white, (2–)3–6-armed bushy to substellate hairs 0.2–0.25 mm diam, margin densely shortly hairy with same hairs ( Fig. 3e ), blade otherwise mainly lacking hairs except thinly scattered white hairs; sessile, red depressed-globose glands 0.05 mm diam scattered throughout; lower surface with midrib 10–20 % covered in dark brown ‘dagger hairs’ 0.5–0.6 mm long, mixed with substellate pale brown bushy hairs arising from a dark red base, 4–6-armed, 0.15–0.2 mm diam, extending very sparsely to the blade (i.e. Elmer 14248) or moderately densely c. 3 hairs mm 2; margin densely ciliate with hairs as in upper surface of midrib. Petiole winged, broadly U- or V-shaped in section, (6–)7–10 by 0.6–1(–2) cm. Lower pitchers (tendril not coiled) ellipsoid-cylindric, 9–14 by 2.5–5 cm, widest in the ellipsoid lower half, upper half cylindric 1.5–2.5 cm wide; fringed wings present from base to peristome, wings 3–4 mm wide, fringe elements 4–5 mm long, (2–) 3–5.5 mm apart; outer surface 30–50 % covered in minute (3–)4-armed stellate hairs 0.1 mm diam, mixed with sparser (c. 5 % cover) hairs 0.75–1.3 mm long superficially simple but bearing 1–2 short side branches from the central axis ( Fig. 3j ). Mouth ovate-elliptic, 2.5–4 by 1.7–2 cm, oblique, not, or only weakly concave, column not present; peristome cylindric 2– 4 mm diam, even in width throughout, ribs 0.5–0.6 mm apart, raised 0.4 mm, in life the inner edge appears to be without teeth or holes, which can be found on dissection, outer edge not lobed. Lid orbicular-elliptic, 2–2.5 by 1.8–2.9 cm, apex rounded, base slightly cordate; basal ridge and appendage absent in the smaller pitchers (c. 10 cm tall), resembling those of the upper pitchers in the larger (c. 15 cm tall) pitchers; nectar glands and indumentum resembling those of upper pitchers but sparser. Spur triangular c. 2.5 by 1.5 mm, tapering from base to rounded apex; densely covered in brown bushy and ‘dagger hairs’ 0.3–1 mm long. Upper pitchers (tendril coiled) ellipsoid-cylindric (9–)16–25 by (2.6–) 4–5.5 cm, widest in the basal ellipsoid, 7–8 cm long portion, above cylindric narrowed to (1.8–)2.5–3(–3.5) cm diam; indumentum as lower pitchers, colour when live with basal, swollen part of pitcher green (drying brown), overlain with white waxy layer, cylindrical part with faint to well-marked longitudinal red-purple stripes and flecks, inner pitcher surface waxy green (drying pale purple), spotted with purple; fringed wings present only immediately below the peristome (0.6–) 1.7–3.5 cm long, widest at the peristome where (1–) 2.5–7.5 mm wide, fringed elements 3–6 mm long, 1.5–3 mm apart, the uppermost longest and raised above the peristome; mouth ovate, 3.5–5 by 2.5–3.3 cm, oblique, slightly concave, column weakly developed; peristome subcylindric (flattened only before the pitcher is fully opened Fig. 3b ) (1.5–)2–3(–5) mm broad, ribs 0.3 mm apart, about 0.01 mm high, outer margin entire, revolute, inner margin without conspicuous teeth, revolute (edge with holes visible only when dissected, ( Fig 3q ), green or red and green in colour; lid ovate (2.2–)3.3–4.5(–4.9) by 2.5–4(–4.6) cm, apex rounded or slightly retuse, base cordate, the sinus 1–1.5 cm wide, 5 mm deep, lower surface with a basal ridge 1.5 cm long, rising gradually to 0.5–1 mm high, tapering to the extremities, and bearing in the centre a convex or recurved-hooked appendage ( Fig. 3n ) projecting 3–4 mm from the lid surface, 4–7 mm long; nectar glands are of two types and mostly confined to two approxi- mately lanceolate areas, which are joined at the basal ridge, nectar glands being largely absent from a marginal band 5–8 mm wide and from the distal half of the midline; they are thinly scattered on the basal appendage; type 1: nectar glands (90 % of the total c. 1 per mm 2) are small, thinly bordered, orbicular or elliptic, 0.1–0.2 mm in length; type 2: nectar glands are similar in appearance, but much sparser and larger 0.5–0.6(–0.7) mm long; sessile red-black depressed- globose glands 0.05 mm diam, c. 3 per mm 2 are scattered over the whole of the lower surface; marginal 2–3 mm 50 % covered in stalked bushy brown hairs 0.1–0.2 mm diam, several occurring towards the centre of the lid, 8–10 mm from the edge; spur simple, filiform, 5–9 mm long, 0.5 mm wide, apex obtuse, densely covered in appressed hairs 0.5–1 mm long. Male inflorescence c. 47 by 3.5 cm, indumentum moderately dense, covering 40–50 % of the surface, hairs pale brown, a mixture of ‘dagger hairs’ 0.5–1 mm long, and 2–4-armed bushy hairs 0.2–0.25 mm long; peduncle c. 27 by 0.3 cm; rhachis c. 20 cm long, with partial-peduncles 75–80, 2-flowered (1-flowered at apex); bracts recurved or patent, filamentous, c. 3 mm long, acute, inserted along the length of the partial-peduncles; partial-peduncles 4–6 mm long; pedicels c. 15 mm long, indumentum covering 30–50 % of the surface, hairs bushy, 1–3-armed, erect, 0.2–0.5 mm long; tepals 4, elliptic, 6 by 4 mm, outer surface 50–60 % covered in a mixture of simple, acute hairs 0.15–0.25 mm long, and sessile mucilaginous papillae 0.005 mm diam, inner surface densely covered in elliptic nectar glands; staminal column 5 mm long, moderately densely hairy along its length, hairs 0.1 mm long, more or less patent, red-brown, simple or with a basal branch; anther-head subglobose, 2.5 mm diam. Female inflorescences, infrutescences and seed unknown.

Distribution & Ecology — Philippines, NE Mindanao, Mts Masay and Pasian, submontane mossy forest along ridges, thought to be non-ultramafic, 1500–1875 m asl.

Additional material. PHILIPPINES, Mindanao , Mt Masay (also known as Mt Cabadbaran and Mt Urdaneta), Elmer 14248 ( E, L), “in the summit region at approx. 6250 feet alt., Oct. 1912 ” ( Elmer 1915) .

Conservation — Nepenthes zygon is known with certainty from only two individuals at two locations, in a country which has seen loss of most of its natural habitat in the 20th century ( Myers et al. 2000, Sohmer & Davis 2007). Nepenthes zygon shares its type location, Mt Pasian, with N. robcantleyi . The clear-felling of forest there that led to the concern that N. robcantleyi might be extinct ( Cheek 2011) may also have elimi- nated N. zygon at that location. However at its second location, Mt Masay, no threats are yet known to summit areas where N. zygon was collected (Gronemeyer pers. comm. to MC). Recent photographic records of what may be this species (identified as N. alata in Gronemeyer 2008: 26, 2009: 7) at Mt Masay suggests that it survives there. A similar image from Mt Hibok-Hibok ( Gronemeyer 2008: 25) suggests that N. zygon may also be present there, yet all three images do not provide enough detail that identification is certain. Accordingly, N. zygon is here assessed as Critically Endangered under IUCN (2012), criterion D based on less than 50 individuals (in fact two) being known from the wild with certainty. It is to be hoped that the species will be verified at the locations named above, found at additional locations and so proved to be not so rare or threatened as existing data suggest. It is fortunate that N. zygon is already in cultivation and available commercially from the nursery Borneo Exotics.

Taxonomic affinities — Although N. zygon has previously been identified as N. alata in the broad sense, recent research has shown that the latter species is confined to northern Luzon and differs in a number of characters (see key). Nepenthes zygon appears to be closely related to N. mindanaoensis , being very similar in overall appearance. Their geographic ranges coincide, but ecologically they are separated by their habitat and altitudinal range, N. zygon being restricted to cloud forest on non-ultramafic substances, while N. mindanaoensis is restricted to low altitude ultramafic scrub. Nepenthes zygon lacks the diagnostic petiole of N. mindanaoensis in which the wings are so involute that their margins overlap each other so that the petiole appears cylindrical. Nepenthes zygon also has a well-developed basal appendage to the lid (vs being absent), besides differing in the other characters given in Table 3.

Nepenthes zygon has several features unusual in the genus, and which are otherwise unknown in the N. alata group. These are:

1. the white waxy bloom that coats the lower half of the upper pitchers;

2. the presence of hairs in the centre of the lower surface of the lid of the pitcher; and

3. the dense patent hairs of the androphore (although male inflorescences are not known for all species of the group).

Variation — The two collections vary from each other in density of indumentum on the stem and lower surface of the leaf-blade of the climbing stem (very sparse in Cheek 17059, moderately dense in Elmer 14248) and in the density of the nectar glands on the lower surface of the lid of the upper pitcher, which is much sparser in Elmer 14248 than in Cheek 17059. In all other respects, the two specimens appear more or less identical, e.g. in the unusual trichome complement of the leaf-blade midribs and lower lid surface.

Notes — “Three or more distinct terrestrial species” (of Nepenthes ) were observed “in the summit region or about 5000 feet ” by Elmer on Mt Masay (also known as Mt Urdaneta or Mt Cabadbaran) ( Elmer 1915). These were all collected by Elmer: N. surigaoensis Elmer (Elmer 12705 in Sept. 1912), N. petiolata Danser (1928) which had been collected by Elmer as a mixed gathering with the first species, although Elmer had suspected that it was different when he had collected it ( Elmer 1915). Thirdly, newly described here from the same locality (although the altitude given is higher), N. zygon (collected in Oct. 1912). From neighbouring peaks “at a lower elevation there is the high epiphytic species N. truncata Macf. “ ( Elmer 1915), which Elmer had collected earlier in Aug. 1912 although he gave it a higher collection number (Elmer 13483, BM, Urdaneta).

Macfarlane (1927) in his final paper of Philippine Nepenthes , misidentified Elmer 14248 citing it as N. alata var. ecristata Macfarl. (1908: 72) , the type of which is now raised to species rank as N. kurata Jebb & Cheek (2013h) . It can be distinguished using the key above. Danser (1928) cited the same specimen simply as N. alata , taking a wide view on the delimitation of this species.

In life (Cheek 17059), the colour and aspect of the upper pitchers is very different from the herbarium specimens (Elmer 14248), but once the former had been dried, these features became identical to the second, although made 101 years later. Nepenthes zygon , although newly described here, is already one of the better-known Mindanao species of the genus, because it has been possible to observe authentic wild-sourced material in cultivation from the juvenile stage to flowering, and so to develop a nearly complete description. This approach is also used in Araceae where leaves and inflorescences do not occur on the plant at the same time so that cultivation is the best way to reliably connect the different stages for descriptive purposes.

The basal ridge and appendage that characterise the N. alata group, and which are present in the upper pitchers of N. zygon , are completely absent from its lower pitchers. Whether this is usual or not throughout the species of the group remains to be determined.

Figures

Fig. 3 Nepenthes zygon Jebb & Cheek. a. Habit, climbing stem with male inflorescence and upper pitcher; b. upper pitcher, not yet fully opened; c. lower pitcher; d. leaf-blade, upper surface showing midrib hairs; e. leaf-blade, marginal hairs; f. rhachis indumentum; g. partial-peduncle with male flowers; h. pedi- cel indumentum; i. tepal, lower surface indumentum; j. upper pitcher, outer surface indumentum; k. tendril indumentum; l. lid of upper pitcher showing nectar gland distribution and basal appendage; m. lid, lower surface, detail of glands; n. lid basal appendage (inverted); o. spur, upper pitcher; p. peristome viewed from above; q. peristome, viewed from inside pitcher, unrolled to expose inner edge; r. peristome, transverse section, immature, outer surface on right (a–k, m–r. from Cheek 17059 (drawn from live material); l. from Elmer 14248 (E). — Scale bars: a–c = 5 cm; d–f, h, i, k = 1 mm; g, l, n = 1 cm; j = 2 mm; m, o–r = 2 mm. Drawing by Andrew Brown.