Pinguicula colimensis — Vorstman's Guide to the Carnivorous Plants

Identification

In the dry season a small winter rosette of short leaflets 10 to 20 mm long is all that remains. In the rains the plant changes completely: the summer leaves become obovate-oblong, 60 to 120 mm long and 30 to 65 mm wide, spread flat with a dense glistening glandular coating. Scapes reach 6 to 14 cm, sometimes 19 cm. The flower measures 35 to 50 mm including the spur and is deep pink to crimson; the spur is slender and long, (20) 25 to 35 (40) mm, projecting well behind the flower. Flowering falls in and after the rainy season, July into December. The size of the summer rosette and the colour of the flower make the species conspicuous in the field.

Similar species

The large broad summer leaves combined with a long spur and a pink to red flower separate the species from most relatives. Pinguicula moranensis, which occurs in parts of the same region, has smaller leaves and a flower usually more violet than red. P. macrophylla also has large leaves but a markedly violet-purple flower and grows higher in the mountains. Out of flower the size of the summer leaf is already a strong character: few Mexican butterworts grow so broad.

The trap and how it works

A flypaper trap on a large flat leaf, and so one of the most generous catching surfaces in the genus in Mexico. The stalked glands carry a droplet of sticky mucilage; the sessile glands between them release enzymes on contact. The leaf margin then rolls slowly over the prey, so the fluid stands in a shallow bowl instead of running off the steep rock face. Because the leaves are so broad, moisture is held among the glands even during a heavy tropical shower. In this warm lowland the catch is varied and plentiful: midges, flies, ants and all sorts of small walking insects.

Habitat and ecology

Steep to vertical limestone and gypsum walls, often facing north, in a warm and markedly seasonal climate (R1, R2). The plants grow on ledges, in crevices and where water runs over the wall; in the dry months that supply all but ceases and the plant withdraws into the winter rosette. Elevation is low for a Mexican butterwort — a few hundred metres — which means high temperatures and a short, heavy rainy season. The accompanying vegetation is deciduous tropical dry forest and open scrub at the foot of the wall.

Distribution and elevation

Known from western and south-western Mexico: Colima, with adjoining sites in Michoacán and Guerrero. Our species list names Colima, which matches the type locality, but the range reaches beyond that one state. The species is endemic to Mexico. It is a distribution of isolated walls and gorges in the hill country behind the Pacific coast rather than a continuous area; between the sites lies landscape wholly uninhabitable for this plant.

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 are distinguished. Flower colour shifts between populations from deep pink to nearly crimson, and spur length varies considerably too, from two to four centimetres. Leaf size depends mainly on how much water a wall holds during the rains: on the wettest walls the summer leaves grow largest. No natural hybrids with other butterworts have been published from the sites, which is unsurprising given how isolated the walls are.

Where and when to see it

Search from August to November, when the summer rosettes are full-grown and the flowers stand above them; in the dry months there is barely anything to see. Look at the wall, not the ground, and concentrate on wet shaded stretches where moss and ferns grow. The pink flowers show well from a distance against the pale limestone. These are steep walls in a hot climate; stay on the path, avoid the middle of the day and carry plenty of water.

Conservation status

Not assessed for the global IUCN Red List, and not listed in CITES. It is known that the species occurs on a limited number of walls in western Mexico and can stand there locally in fair numbers. The risks named are limestone and gypsum quarrying, road building through the gorges, and fires in the surrounding dry forest reaching the foot of the wall. Published counts do not exist, and that is precisely what an assessment would require. The species is present in cultivation, so collecting in the wild is unnecessary.

Scientific name

Pinguicula colimensis | McVaugh & Mickel, 1963

Described by Rogers McVaugh and John Mickel in 1963. The type area lies in the Mexican state of Colima, where the species grows on vertical gypsum rock at around 450 metres elevation, some 30 kilometres from the Pacific coast. The species name colimensis refers directly to the state of Colima, where the species is endemic.

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