All species › Lamiales › Bladderwort family › Pinguicula gigantea
Pinguicula gigantea
The largest butterwort in Mexico, and one of the few you can pick out on a rock face from a distance. Pinguicula gigantea forms a rosette that comfortably exceeds an adult palm, with leaves that shine in the sun as though oiled. The species was only described in 1995, from plants on the steep walls above the Río Uruapan near San Bartolomé Ayautla in Oaxaca, and it is known in the wild from a mere handful of sites.
Identification
A flat, strikingly large rosette. The leaves are 6 to 14.5 cm long and 4 to 7 cm wide, broadly spathulate to obovate, light green, with a margin that stands slightly upward on older leaves. The character separating the species from every other Mexican butterwort is that the glands sit not only on the upper surface but also on the underside of the leaf: the plant catches on both faces. One to several straight scapes 15 to 18.5 cm tall rise from the centre. The flower measures 28 to 33 mm including the short, blunt spur of 5 to 8 mm, and is pale purple-violet to whitish lilac; populations with pure white flowers also exist. Flowering falls in the dry months, January to April. Unlike most Mexican species, P. gigantea does not form a tight fleshy winter rosette but carries on with smaller carnivorous leaves.
Similar species
On size alone confusion is barely possible: no other Mexican butterwort grows so large. The nearest is Pinguicula moranensis, far commoner in the same country; that has a smaller rosette, a much longer spur and a deeper-coloured flower. In the field the underside of the leaf settles it: if it is smooth and glandless, the plant is not P. gigantea. Young, not yet full-grown plants can resemble large P. moranensis; then wait for flowering, because the short spur of P. gigantea is immediately decisive.
The trap and how it works
A flypaper trap, and in this species a double-sided one. The leaf carries stalked glands each holding a clear droplet, and between them sessile glands that release digestive enzymes only when prey is actually lying there. An insect that lands sticks fast; struggling brings more droplets into contact and smears the animal. Then a slow movement begins: the leaf margin rolls a little way towards the prey so the digestive fluid does not run off the sloping wall. Because the underside of the leaf is sticky too, the plant catches insects crawling up the overhanging rock from below — a supplement no relative shows so clearly. The prey is mostly midges, small flies and ants.
Habitat and ecology
Steep to overhanging limestone walls in a warm tropical valley, a few hundred metres above sea level. The area receives very heavy rain — figures around three thousand millimetres a year — but strongly concentrated in summer, so that the wall stands almost dry for months in winter. The plants grow in crevices and on ledges in full sun, among bromeliads such as Tillandsia streptophylla and agaves; they share their site with pronounced drought plants. The water comes from seepage and from the very high humidity in the valley (R1, R2). Soil in the ordinary sense is almost absent: what holds the roots is a thin layer of moss, grit and humus in a crack.
Distribution and elevation
Known from northern Oaxaca, from the area around San Bartolomé Ayautla in the Cañada, where the species grows on the southern walls above the Río Uruapan. The number of known sites is small and the species is a Mexican endemic. Its elevation is remarkably low for a Mexican butterwort: a few hundred metres, where most relatives only begin above a thousand. Our species list gives Oaxaca, which matches what has been published about the wild populations.
- Recorded (one-degree cells)
Forms and variation
In the wild variation is limited and no varieties have been described. What is reported is a difference in flower colour between populations: besides the usual pale purple-violet form there are plants with nearly white flowers. Otherwise plants differ mainly in size, and that seems largely to reflect how much moisture and humidity a given ledge holds; on the most exposed spots the rosettes stay distinctly smaller. Natural hybrids with other butterworts have not been reported from the sites, which is to be expected, since no other Pinguicula grows nearby.
Where and when to see it
The best months are January to April, at the end of the dry season, when the rosettes are largest and the flowers stand above them. Do not search the ground but look up: the plants sit on the wall itself, often several metres above the road or the river, and are better viewed with binoculars than from close by. Raking light makes the glandular coating glint, after which the rosettes stand out as wet pale patches against the grey limestone. Stay on the road or path; the walls are steep, loose, and with their agaves and bromeliads unpleasant to climb.
Conservation status
The species has not been assessed for the global IUCN Red List and is not listed in CITES. What is certain is that the known range is very small: a handful of walls in one valley in Oaxaca. That makes it sensitive to local works — road building along the river, clearing of cliff vegetation and collecting for the trade are all named as pressures. Since the plant is widely available in cultivation and easily propagated from leaves, there is no reason to take wild specimens. The absence of an assessment here says more about the attention the species has received than about its safety.
Scientific name
Pinguicula gigantea | Luhrs, 1996
Described by Hans Luhrs in 1996, in Phytologia 79(6): 389–392, based on material collected by the botanist Alfred Lau. The type area lies near San Bartolomé Ayautla, in the Mexican state of Oaxaca, on steep cliffs along the Río Uruapan. The species name gigantea is Latin for "gigantic" and refers to this species' notably large size compared to other Pinguicula species.
World Checklist of Vascular Plants (WCVP), via Plants of the World Online (POWO), Royal Botanic Gardens, Kew.