Pinguicula emarginata — Vorstman's Guide to the Carnivorous Plants

Identification

The rosette consists of elliptic to obovate leaves 10 to 50 mm long and 3 to 22 mm wide, spread flat against the wet rock with a dense glandular coating. The scape reaches 4 to 10 cm and usually carries one flower. The flower is small, 8 to 16.5 mm including the spur of 4 to 7 mm, and white with purple veining or entirely deeper violet; on the median lobe of the lower lip sits an even, bright lemon-yellow blotch pointing the visitor to the throat. The tips of the corolla lobes are notched — hence the epithet. The spur is straight to slightly curved. Unlike many Mexican species the plant forms no tightly closed winter bud and flowers almost year-round. Because the plant carries leaves all year, one rosette often shows flowering scapes, ripening capsules and fresh leaves at the same time — a picture that never occurs in most Mexican relatives, with their sharp division between dry and wet season.

Similar species

A yellow throat blotch on an otherwise white or violet flower with notched lobes is unusual among Mexican butterworts and makes the species readily recognisable. Pinguicula moranensis, growing in the same mountains, is much more substantial and has a spur over a centimetre long. P. lilacina also has a yellow throat mark, but is annual, has no notched lobes and grows on rocky woodland soil rather than on wet walls. In doubt, the combination of site — a wet sandstone wall — and notched lobes decides.

The trap and how it works

A flypaper trap working almost year-round, which in Mexico is the exception rather than the rule. On a permanently wet wall in cloud forest the plant need form no drought bud, so the glandular coating stays in business continuously. The stalked glands hold the prey, the sessile glands supply enzymes on contact, and the leaf margin rolls slowly towards the prey so the fluid stays. The supply of prey is generous: clouds of small flies hang permanently around waterfalls and damp walls in subtropical cloud forest.

Habitat and ecology

North-facing sandstone walls with a thin wet layer of humus on the rock, beside streams and waterfalls in subtropical cloud forest (R1, B1). The accompanying vegetation consists of epiphytic bromeliads, orchids and tree ferns; the air is permanently humid and the wall never dries out entirely. The elevation range is narrow, roughly fourteen hundred to sixteen hundred metres. Precisely because the rock is steep and wet, no real soil accumulates and there is little competition from larger plants. What is special about this site is that the water comes not from the soil but over the rock: a thin, permanent film that the high humidity never lets evaporate. That makes the species wholly dependent on the flow of the stream above it.

Distribution and elevation

Endemic to Mexico, with sites in Veracruz and Puebla, among them the municipality of Atzalán and the area between Teziutlán and Tlapacoyan. Our species list says north-eastern Mexico; that is both too broad and too far north, since the known populations lie in the east, on the humid eastern flank of the Sierra Madre Oriental. We follow Veracruz and Puebla here. The range is small and tied to a narrow cloud-forest belt.

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 3 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 species is strikingly variable in flower colour: some populations are white with purple veining, others entirely deeper violet, while the yellow throat blotch is present in all plants. No wild varieties are distinguished and the variation is gradual. Leaf size differs greatly between plants on a permanently wet wall and those on a drier ledge: the published figures run from one to five centimetres. No natural hybrids have been published from the sites.

Where and when to see it

This species can be found in flower almost all year, so planning is easy; the rainy-season months do give the most flowers at once. Search along streams and by small waterfalls, on the wet shaded sandstone walls, and look for the yellow throat blotch — it catches the eye sooner than the pale flower around it. Do not touch the thin layer of humus on the rock: it comes away at a touch and takes the plants with it. For photographs, overcast weather beats sun, since the wall is glistening wet.

Conservation status

Not assessed for the global IUCN Red List and not listed in CITES. What is known points to a species with a small range in a vulnerable environment: the cloud forest on the eastern flank of the Sierra Madre Oriental has been much reduced by coffee growing, cattle farming and logging, and the wet walls where the species grows often lie along roads and tourist waterfall routes. Water abstraction upstream is a second risk, since if the wall dries the plant goes. There are no published population figures; an assessment would be well placed here.

Scientific name

Pinguicula emarginata | Zamudio & Rzedowski, 1986

Described by Sergio Zamudio and Jerzy Rzedowski in 1986, in “Tres especies nuevas de Pinguicula (Lentibulariaceae) de México”, Phytologia 60(4). The type area lies near Tatzayanala, in Atzalan municipality, in the Mexican state of Veracruz, on rocks along a riverbank at 1400 metres elevation. The species name emarginata is Latin for "notched" and refers to the irregularly notched lobes of the corolla.

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