Pinguicula crassifolia — Vorstman's Guide to the Carnivorous Plants

Identification

A species with clearly dimorphic leaves. The summer leaves are large and elliptic, 37 to 111 mm long, thin and bearing the usual sticky droplets on the upper surface; they lie flat on the moss or hang slightly over the rock. The winter rosette is made of far smaller, strikingly thick and fleshy leaves only 3 to 11 mm long — hence the epithet. The flower is large for a Mexican butterwort: 23 to 50 mm long, red-purple, with a cylindrical spur 8 to 25 mm long. For flowering time we could find no testable statement, so that field has been left empty on the fact card. Out of flower the plant is recognisable by the combination of large summer leaves and a surprisingly small, thick-leaved winter bud.

Similar species

At this altitude the choice of species is limited, which helps. The large-flowered species of the Pinguicula moranensis complex occur in the same part of Hidalgo but generally stay lower and have a looser, leafier winter rosette with longer winter leaves; the extremely short, thick winter leaves of 3 to 11 mm are diagnostic for P. crassifolia. Pinguicula elizabethiae, also from Hidalgo and Querétaro, grows lower and on limestone. If you are in the fir forest of Parque Nacional El Chico and see a large red-purple flower, this is probably the species; lower down, in the oak zone, the odds change.

The trap and how it works

The large thin summer leaves do the catching. Their upper surface carries stalked glands with a sticky droplet, and between them sessile glands releasing digestive enzymes only on contact with prey; the leaf margin then curls slowly over the catch. In a cool, permanently damp fir forest at three thousand metres the catch is mostly midges, crane flies and other small two-winged insects swarming above the wet mossy rocks, supplemented by springtails from the moss mat itself. The thick winter leaves do not feed: they exist to carry the plant through the cold, dry months, when the forest freezes at night and few insects fly.

Habitat and ecology

Moss-covered wet rocks in forest of Abies religiosa and Juniperus, at 2850 to 3000 m. The plants sit in shaded, damp rock crevices where some organic matter has gathered, at spots where seepage or rainwater runs over the rock (R1), under the closed canopy of the fir forest or at its edge (B5). It is a cool wet environment rich in mosses and ferns but with almost no soil: nutrients are washed away continuously, which is what makes carnivory worthwhile here. At this altitude night frost and snow are regular, and the plant passes that period as a thick-leaved bud.

Distribution and elevation

Endemic to the state of Hidalgo in central Mexico, described from Las Ventanas in the municipality of El Chico, and known from Parque Nacional El Chico and its immediate surroundings — the highest part of the Sierra de Pachuca. Our species list gives Hidalgo and Veracruz; the original description and the type material point to Hidalgo alone, and we could find no confirmation for Veracruz. The known range is therefore very small: a single massif, within an altitudinal band of less than a hundred and fifty metres. That it falls within a national park is a favourable circumstance for its protection.

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

No wild varieties have been described. In a species confined to one massif and a narrow altitudinal band that is to be expected: the environment is much the same throughout, with the same rock, the same forest type and the same climate. Observed variation concerns the size of the summer leaves, substantial in deep wet crevices and small on exposed rock, and the length of the spur, which according to the description varies strongly — from eight to twenty-five millimetres. That spur variation within a single species is a warning against leaning too heavily on spur length when identifying Mexican butterworts. No natural hybrids are reported.

Where and when to see it

Go in summer, when the summer rosettes are fully out, and search the damp north-facing rock formations in the fir forest of Parque Nacional El Chico: the park's well-known rocks and crags are exactly the right kind of site. Look into crevices and under overhangs where water seeps down the face and the moss is thick. The large red-purple flower carries at a distance; the rosette merges into the moss. At this altitude the weather turns fast — take rain gear and do not scramble over the rocks in mist. Leave the plants alone; the populations are small and lie in a protected area.

Conservation status

The species has not been assessed for the global IUCN Red List and is not listed in CITES. What is known is quickly summarised: a pronounced high-mountain species with a very small range in a single massif, which puts it squarely in the category where an assessment ought to follow. In its favour is that most of the range lies within a national park and that the fir forest there is maintained. Against it are the recreational pressure on exactly the rock formations the species occupies, the fires that periodically strike the park forest, and shifting climate belts: for a species already at the top of its mountain there is no higher ground to move to. The absence of an assessment here is a gap, not reassurance.

Scientific name

Pinguicula crassifolia | Zamudio, 1988

Described by Sergio Zamudio in 1988, in Acta Botanica Mexicana 3: 21–28. The type area lies in El Chico municipality, near Las Ventanas, in the Mexican state of Hidalgo, at around 3000 metres elevation. The species name crassifolia combines the Latin crassus ("thick") and folium ("leaf") and refers to this species' notably thick, fleshy winter leaves.

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