Heliamphora uncinata

No photograph of this species under a Creative Commons licence or in the public domain is in the guide yet.

Identification

A rosette of erect to slightly overhanging pitchers about 25 to 35 cm long and 8 to 10 cm wide at the mouth — a substantial plant by the standards of this genus. Each pitcher is a single leaf grown shut into a funnel with a seam down the front. The mouth is circular, with the back drawn up into a raised portion that hangs over the opening like a small roof. The diagnostic character stands on top of it: the nectar spoon is distinctly hooked, curved forwards and down, and is almost always red — even in plants that are otherwise entirely green. Pitcher colour is strikingly even light green; only with more light does it turn orange-red. In freshly opened pitchers a strong blue fluorescence has been observed under ultraviolet light, which disappears again in older pitchers on the same plant. Measurements of the scape and floral parts are not established in accessible literature.

Similar species

The species closest to it in structure and habitat is Heliamphora exappendiculata, widespread in the same massif and likewise a plant of wet rock faces; uncinata is thought to have arisen from it. Pitcher shape, growth habit and the look of the nectar organ are similar, which makes the hooked, red spoon of uncinata the most usable field distinction: in exappendiculata that organ is reduced to almost nothing. Heliamphora pulchella also occurs in the Chimantá massif, but is much smaller, densely hairy inside and grows in peat rather than on rock. Other relatives on the massif stand on the open plateaus and not in the canyons. Confusion with Sarracenia is ruled out geographically.

The trap and how it works

A pitfall trap of some size, which leaves the digesting largely to bacteria: the plant makes few or no enzymes of its own and takes up the nitrogen and phosphorus the bacteria release. The hooked nectar spoon is the lure; its curve holds it over the opening, so an insect seeking the nectar is positioned directly above the trap. The upper part of the inner wall carries downward-pointing retentive hairs that make climbing back out impossible; it is precisely those hairs that light up under ultraviolet in a freshly opened pitcher. Whether that light genuinely serves to lure is uncertain — in this species the effect vanishes as the pitcher ages. Below that the wall is smooth. The site ensures a constant supply of water, so the trap never dries out.

Habitat and ecology

A narrow canyon within the table-mountain massif (R4), and within it the wet rock face (R1). The plants root directly on sandstone kept permanently wet by water coming down from the plateau above, and otherwise in humus pockets and cracks in that same rock. This is therefore a site without soil in the ordinary sense: the nutrients available are whatever has accumulated in a crevice, and every downpour washes part of it away again. The canyon is also shaded, which explains why the pitchers usually stay an even light green rather than flushing red. The climate is cool and all but permanently wet. Under these conditions — permanent water, permanent shortage of nitrogen — a trap that converts insects is the only realistic route to nutrients.

Distribution and elevation

The species is endemic to Venezuela and so far known only from its type locality: a single narrow canyon in the Chimantá massif, at about 1850 m. The massif holds countless canyons, and since only a small part of them has ever been visited botanically, that single site says more about the level of survey than about the real distribution; the species may well occur elsewhere in the same system. A fine-grained map cannot be made: the international distribution databases hold no distribution region at all for Heliamphora uncinata, so what stands here rests entirely on the taxonomic literature. Precise sites are left out. The genus as a whole is confined to the table mountains of the Guiana Shield.

Forms and variation

No varieties or subspecies have been described, which is hardly to be expected for a species known from one canyon. Such variation as there is concerns colour and depends on how much light a plant catches: in the shade of the canyon wall the pitchers stay an even light green, in the brighter spots they flush orange-red. The nectar spoon stays red either way. No natural hybrids have been recorded for this species, but the relationship with Heliamphora exappendiculata is so close that crosses cannot be ruled out where both stand within a short distance on the same wall; this has not, however, been investigated.

Where and when to see it

The Chimantá massif is reachable only by helicopter or on a long trek and lies within Canaima National Park; visits are made with a permit and a guide. Anyone descending into a canyon should not search the floor but look up: the plants sit on the wall itself, in the track where water seeps down, and in the crevices beside it. The first thing you usually see is not the pitcher but the red spoon, standing out against the evenly green wall. Do not confuse the species with the far more widespread rock-face species of the same massif; look at the nectar organ, which in that one is all but absent. Do not climb over the occupied stretches of wall; the roots sit in thin films of humus that come away easily.

Conservation status

The species has not been assessed for the IUCN Red List and there is no CITES listing: Heliamphora appears in no appendix. What can be said is that the known distribution is confined to a single canyon, the smallest range in the genus. That figure should be read with caution, because the massif has barely been surveyed and the species may stand elsewhere in the same system. Against that, the habitat lies within a national park and World Heritage site, the canyon cannot be reached without a permit and a helicopter, and a rock face is considerably harder to strip than an open bog. Collection for trade is the risk routinely named for the genus, but cultivated material now comes almost entirely from seed and tissue culture. The absence of an assessment here follows above all from the lack of field data.

Scientific name

Heliamphora uncinata | Nerz, Wistuba & Fleischmann, 2009

Described by Joachim Nerz, Andreas Wistuba and Andreas Fleischmann in 2009, in Willdenowia 39(2): 273–283. The type area lies in a narrow canyon on Amurí-tepui, at around 1850 metres elevation, on sandstone cliff faces. The species name uncinata is Latin for "hooked" and refers to a hook-shaped structure in the plant's build.

World Checklist of Vascular Plants (WCVP), via Plants of the World Online (POWO), Royal Botanic Gardens, Kew.