Heliamphora glabra — Vorstman's Guide to the Carnivorous Plants

Identification

A rosette of erect pitchers, each formed from a single leaf grown shut into a funnel with a seam down the front. The character that gave the species its name is hairlessness: where related species of the eastern tepuis have a distinctly hairy pitcher interior, here it is largely glabrous, apart from the band of retentive hairs below the rim. On the back rim stands the nectar spoon, the small hooded organ that in this genus takes the place of the broad hood of Sarracenia. In measurements of ultraviolet fluorescence across the genus, this species proved to light up essentially only at that spoon and not over the rest of the pitcher — an indication that the luring is strongly concentrated on that one point. Pitcher colour runs from green to reddish as the site becomes more open. Measurements of pitcher, scape and floral parts are not established for this species in accessible literature and are therefore left blank here.

Similar species

The main confusion is with Heliamphora heterodoxa, the species under which this plant sat as a variety for more than a quarter of a century. The distinction is precisely what the name says: the pitcher interior is glabrous in glabra, distinctly hairy in heterodoxa. That can be checked in the field with a hand lens and settles the matter in cases of doubt. On the Roraima group Heliamphora nutans also occurs, with larger, more strongly nodding pitchers and a differently shaped nectar spoon. Because glabra spans an altitudinal range of more than a kilometre and a half, size is no guide: plants from the lowest sites and plants from the highest differ greatly. Confusion with Sarracenia is ruled out geographically.

The trap and how it works

A pitfall trap and, as everywhere in this genus, one that leaves the digesting largely to others. The plant makes few or no digestive enzymes of its own; bacteria in the pitcher fluid break the prey down and the plant then takes up the released nitrogen and phosphorus. The nectar spoon on the back rim secretes nectar and draws insects to precisely the edge of the opening. The upper part of the inner wall carries downward-pointing hairs, so climbing back out is impossible; below that the wall is smooth. A drainage opening in the wall keeps persistent rain from overflowing the trap and washing the catch away. That the rest of the pitcher does not fluoresce in this species makes the nectar spoon all the more the single point of signal.

Habitat and ecology

The summits and high plateaus of the eastern table mountains (R4), where soil is all but absent and acid peat with bog moss gathers only in hollows and fissures (W1). The species also grows on wet rock faces and slopes kept permanently damp by seeping water (R1). The altitudinal range is remarkably wide for the genus: from about 1200 m to around 2750 m. At that upper limit, on the highest slopes, the plants stay conspicuously small and stunted — these are the most extreme sites known for the species. Across that whole range the climate is cool to cold, all but permanently wet, with cloud covering the mountains much of the day. Everywhere the substrate is extremely poor in nutrients, and rain continually washes away what little there is.

Distribution and elevation

Unlike most of its relatives this species is not confined to a single table mountain. Known sites are spread over the eastern tepuis around the border region of Venezuela, Brazil and Guyana — among them Roraima, Wei Assipu-tepui, Serra do Sol and Maringma-tepui — between about 1200 and 2750 m. Global checklists give Venezuela and northern Brazil (Roraima state) as the range; in Brazil the species is not regarded as endemic. Precise sites are left out here. The genus as a whole is confined to the table mountains of the Guiana Shield, and this species in particular shows that those islands have at times been connected after all: a contiguous group of mountains can share one species.

Recorded (one-degree cells)

Distribution based solely on records at GBIF (Global Biodiversity Information Facility), not on TDWG regions — those are often far larger than the actual range. The light halo is the area around a record, the dark core the record itself. The darker cells are 2 one-degree squares — roughly a hundred and ten kilometres — in which the species has been recorded, from all GBIF records. This is coarser than for most species because hardly any record of this plant carries an accurate coordinate: the locality of poached species is obscured at source. At this scale that obscuring disappears into the noise. The cells show where it has been seen, not where it occurs: an empty square means nothing.

Forms and variation

The taxonomic history of the species is itself a history of forms: it was described as a variety of Heliamphora heterodoxa and was also treated as a forma before becoming a species in 2006. At present no varieties are recognised within glabra. What does exist is unnamed variation across the altitudinal range: on the highest slopes the plants stay small and stunted, lower down they are substantial, and colour runs from green in shelter to reddish at open sites. Natural hybrids are regularly reported in this genus wherever two species grow side by side; for this species no named natural hybrid is recorded in accessible literature, which is not the same as certainty that none exists.

Where and when to see it

The mountains this species grows on are among the more accessible in the region — Roraima has an established route — but you will not get there without a permit and in practice not without a guide, and the trek takes days. Once on top it pays to keep a hand lens ready: the difference from its hairy relative lies inside the pitcher and is hard to judge with the naked eye. Look in two places: in the wet hollows of the plateau and at the foot of rock faces where water keeps seeping. Bear in mind that plants from high and low sites look very different; do not let size mislead you. Stay on the established routes — the vegetation on these summits recovers extremely slowly.

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 of all species in the genus this one has among the wider distributions, across several mountains and three countries, and over an altitudinal range of more than a kilometre and a half. That makes it less vulnerable than the species dependent on a single plateau. Against that, the most visited mountain in the region falls within its range, and tourism on a tepui summit does damage that barely heals. The habitat lies largely within protected areas. 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 is a gap in the record, not an established decline.

Scientific name

Heliamphora glabra | (Maguire) Nerz, Wistuba & Hoogenstrijd, 2006

Originally described under a different taxon by Bassett Maguire; published as the distinct species Heliamphora glabra by Joachim Nerz, Andreas Wistuba and Peter Hoogenstrijd in 2006, in Das Taublatt 54: 58–70. The type area lies on Serra do Sol in Venezuela. The species name glabra is Latin for "bald, hairless" and refers to the plant's smooth, hairless surface — a counterpart to the densely hairy H. hispida.

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