Pinguicula mirandae — Vorstman's Guide to the Carnivorous Plants

No photograph of this species under a Creative Commons licence or in the public domain is in the guide yet.

Identification

The winter rosette is striking: a dense bud of (30)40 to 60 small, fleshy, spathulate to oblong-spathulate leaves (7)10 to 20(26) mm long and (2.5)3 to 6 mm wide. The summer rosette has far fewer leaves — (4)6 to 8(10) — thin and obovate-spathulate, 20 to 40 mm long and 14 to 32 mm wide, with the usual glistening droplets. Scapes reach 80 to 100 mm. The flower is small, 9 to 17 mm including the spur, and white, white-violet or blue-violet; the spur is (2)3 to 4 mm. Characteristic is the corolla tube, strongly kinked at midpoint into an angle of about ninety degrees — an identification character settled at once by a side view of the flower.

Similar species

The closest relative is Pinguicula conzattii of the Mixteca, also Oaxacan and also in section Heterophyllum, with the same kinked tube and a winter rosette of many leaves. That species, however, grows far higher, around 2400 m in cloud forest, has a larger flower of 18 to 30 mm, and has winter leaves hairy on both surfaces; in P. mirandae they are glabrous. Within the Tehuacán-Cuicatlán area itself there are no other small butterworts to cause confusion; the large-flowered species of the P. moranensis complex do not occur here.

The trap and how it works

The thin summer leaves carry a flypaper trap of the usual kind: stalked glands with a sticky droplet, sessile glands releasing digestive enzymes as soon as something lies on the leaf, and a margin that bends slowly over the catch. What makes this species distinctive is the timing. In a semi-desert the period during which a thin sticky leaf can function is short, and the plant has concentrated its whole feeding season into the rainy months. Flowering, by contrast, falls in December, in the dry season, when the fleshy winter rosette is in charge. Feeding and flowering are thus separated in time.

Habitat and ecology

Shaded rocky slopes and damp streamside strips in tropical deciduous forest, between about 1250 and 1800 m. The plants grow beneath shrubs in lightly eroded calcareous soils or in crevices of limestone rock (R2), and along the edges of seasonal streams where moisture persists longest after the rains (W7). The surrounding landscape is seasonally dry in the extreme (D4): for months not a drop falls, and only the shade of shrubs and the buffering of a rock crevice make it possible for a plant with sticky leaves to exist here. The fleshy winter rosette is the answer to that drought.

Distribution and elevation

Endemic to the Mexican state of Oaxaca, in the Tehuacán-Cuicatlán valley; the type material comes from the district of Teotitlán, municipality of Santa María Ixcatlán, between Río Seco and Río Santiago. That agrees with the entry in our species list. The area is one of Mexico's foremost centres of plant endemism and has for some years been a World Heritage biosphere reserve, which is favourable for this species. The known range nonetheless remains small and fragmented, spread over separate limestone massifs and ravines in otherwise inhospitable country.

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. Flower colour is, however, notably variable for a species with so small a range: the protologue lists white, white-violet and blue-violet side by side, and flower size runs almost from single to double (9 to 17 mm). Such variation within one population is not unusual in self- or partly self-pollinating species and has not been named as a separate form here — rightly, since there is no evidence that the colour forms are geographically separated. No natural hybrids are reported; no close relatives grow nearby.

Where and when to see it

December is the month, because that is when the species flowers — but be prepared for the plant to look its smallest: the flowers stand above a compact winter bud less than two centimetres across. Search in the shade beneath shrubs and in limestone crevices on north-facing slopes, and along the dry beds of seasonal streams, between roughly 1250 and 1800 m. The white to blue-violet flowers on eight- to ten-centimetre scapes are the only thing visible from a distance. Work slowly and systematically, and take care: in this landscape the plant often grows among cacti and thorn scrub, so watch where you put your hands.

Conservation status

The species has not been assessed for the global IUCN Red List and is not listed in CITES. What is known is a species with a small, fragmented range in the Tehuacán-Cuicatlán area, tied to the moistest microsites of a semi-desert. In its favour, much of that area is protected as a biosphere reserve and the sites — steep limestone slopes and ravines — hold little attraction for agriculture. Against it are overgrazing by goats, which removes exactly the shrub shade the plant depends on, and abstraction of water from the seasonal streams. Without a formal assessment there is no category; the file is thin but not alarming.

Scientific name

Pinguicula mirandae | Zamudio & Salinas, 1996

Described by Sergio Zamudio and Antonio Salinas T. in 1996, in the article "Una nueva especie de Pinguicula (Lentibulariaceae) del Estado de Oaxaca, México", Acta Botánica Mexicana 37: 39–44. The type locality lies in the Mexican state of Oaxaca, Teotitlán district, Santa María Ixcatlán municipality, in the area between Rio Seco and Rio Santiago. Who exactly is honoured by the species name could not be established with certainty.

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