Pinguicula takakii — Vorstman's Guide to the Carnivorous Plants

Identification

A small flat rosette of leaves 5 to 16 mm long and 4 to 12 mm wide, so rarely more than three centimetres across. The scapes stay short, about 25 millimetres, so the flower stands just above the rosette. The flower measures 6 to 12(14) mm including the spur and is violet, with a striking detail: the lower part of the corolla tube and the spur are yellow, and dark red lines run in the throat. The spur itself is small, 2 to 3.5 mm long and about a millimetre wide. For flowering time we found no testable statement; that field has been left empty on the fact card.

Similar species

The gypsum country of San Luis Potosí and adjoining Nuevo León holds other small butterworts, but this species' flower pattern — violet with a yellow tube and spur and dark red throat lines — is unusual in that company: most gypsum dwellers there have a white or pale violet flower with at most a yellow throat patch. Pinguicula gypsicola, also a gypsum dweller from San Luis Potosí, has much longer, narrower summer leaves and a larger flower. Anyone finding a dwarf rosette with a violet-and-yellow flower in this country almost certainly has this species.

The trap and how it works

The small sticky leaves work as a flypaper trap of the usual design: stalked glands with a clear droplet, sessile glands releasing enzymes as soon as prey lies on them, and a leaf margin bending slowly over the catch. On gypsum the catch is no side issue. Gypsum supplies calcium and sulphate in abundance but hardly any nitrogen or phosphorus, and the plants living on this substrate are limited in growth by exactly those two elements. For a butterwort that is an opportunity rather than a constraint. The supply on an open gypsum slope is mostly small flies and ants moving over the bare ground.

Habitat and ecology

Gypsum hills at 1350 to 1400 m, carrying matorral desértico rosetófilo — the scrub of rosette-forming plants characteristic of the dry highlands of central Mexico. The soil is gypsum: hard, white, nutrient-poor and utterly different from the limestone and volcanic substrates on which most Mexican butterworts grow (D4, D1). The vegetation is open and low, and such gypsum soils carry many plant species found nowhere else. The plant exploits the moist period after the rains; through the long dry months there is next to nothing to see above ground.

Distribution and elevation

Endemic to the Mexican state of San Luis Potosí, in the municipality of Villa Juárez, with sites at Minas de Guaxcamá and Minas de San Rafael — in agreement with the entry in our species list. The names of those sites say something about the situation at once: they are gypsum mines, and the species grows on exactly the rock being quarried there. The known range is small and confined to a few gypsum hills. Gypsum outcrops lie scattered as islands through central Mexico, and each island may hold its own species, so neighbouring deposits remain worth investigating.

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 square is the only one-degree cell — 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. It shows where the species has been seen, not where it occurs: an empty square means nothing.

Forms and variation

No wild varieties have been described. The species is known from a few closely spaced gypsum hills within one municipality, which offers too little environmental contrast to hang forms on. Such variation as exists concerns rosette size — the published leaf measurements run from five to sixteen millimetres, a wide spread for so small a plant — and probably tracks the wetness of the spot and of the year. No natural hybrids are reported; no close relatives grow on these gypsum islands with which crossing would be likely.

Where and when to see it

Go after the first heavy rains of the season, when the rosettes are grown and the flowers appear; in the dry season there is virtually nothing to find. Search the white gypsum slopes between the rosette shrubs, on the bare ground rather than in the vegetation, and look from close range: a rosette of at most three centimetres with a one-centimetre flower calls for knees and a hand lens. The violet-and-yellow of the flower shows up surprisingly well against white gypsum. Tread on the gypsum crust as little as possible — it is brittle and breaks underfoot.

Conservation status

The species has not been assessed for the global IUCN Red List and is not listed in CITES. What is known is worryingly concrete: the two sites named are called after gypsum mines, and gypsum extraction means the hill the species grows on is stripped away layer by layer. For a species with a range of a few gypsum hills that is no theoretical risk. Open gypsum slopes in central Mexico are also heavily grazed by goats, and the plant's small size makes it vulnerable to trampling. No category has been assigned because the species has never been examined; an assessment here would probably place it in a threatened category.

Scientific name

Pinguicula takakii | Ruiz & Rzedowski, 1986

Described by Sergio Zamudio Ruiz and Jerzy Rzedowski in 1986, in the article "Tres especies nuevas de Pinguicula (Lentibulariaceae) de México", Phytologia 60(4). The type locality lies in the Mexican state of San Luis Potosí, Villa Juárez municipality, near the Minas de Guaxcama mine, 2 km southeast of Buenavista. The species name honours the Mexican biologist Francisco Takaki, who was the first to collect this species and is known for his contributions to mapping Mexican vegetation.

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