Pinguicula casperiana — Vorstman's Guide to the Carnivorous Plants

Identification

A rosette of yellow-green, oblong leaves, greasy to the touch, glistening with glandular droplets and with margins curled upward; on wet walls they are held obliquely. The scapes are glabrous and each carries one two-lipped flower with a two-lobed upper lip, a three-lobed lower lip and the long cylindrical spur characteristic of this group. Reliable measurements for plant, corolla and spur of this taxon could not be traced to a checkable source for this guide and are therefore not given; the original description in Phytotaxa does supply them, but was not freely available while this account was compiled.

Similar species

The nearest relative is Pinguicula dertosensis from the Ports de Tortosa-Beseit, and the species also stands close to P. mundi, from which it was separated. That is exactly what makes identification difficult: all three are Iberian rock butterworts with long spurs and violet flowers, and the differences lie in flower detail, fruit shape and seed coat. Geography helps most: P. casperiana is the plant of the Serranía de Cuenca, P. mundi that of the Sierra de Alcaraz and the Calar del Mundo, and P. dertosensis that of the north-east.

The trap and how it works

A flypaper trap in a cool limestone gorge. The leaf carries stalked glands with a sticky droplet and, between them, sessile glands supplying digestive enzymes once prey is lying on them. In the permanently humid air along a dripping wall, mosquitoes, midges and gnats fly in quantity, and they make up most of the catch. After a catch the leaf margin rolls towards the prey so the digestive fluid stands in a shallow dish; on a steep or overhanging face that is the difference between digesting and losing it. The limestone and tufa the plant sits on supply almost no nitrogen of their own.

Habitat and ecology

Rocky, calcareous mountain habitats: dripping limestone and dolomite walls, tufa deposits at springs, and shaded gorge faces with water seeping through permanently. Sites lie in the middle to upper zone of the massif and generally face north, out of reach of the summer sun. The plant tolerates no drought: where the water fails in a dry year, the population goes. In the surrounding sierra, bone-dry and hot in summer, these wet walls form sharply bounded islands with their own moisture-loving flora.

Distribution and elevation

The Serranía de Cuenca, across the provinces of Cuenca and Guadalajara in Castilla-La Mancha, in the central-eastern Iberian Peninsula. The range is small and restricted to the limestone gorges of that massif. Our own species list gives only 'Spain' for this taxon; that is too coarse, since the species is defined precisely by its confinement to this one upland, and records from other Spanish sierras belong with the related species.

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 are recognised — for a taxon described only in 2020 that would be premature anyway. Such variation as exists follows the site: plants on the wettest, most shaded faces grow larger and flower more freely than plants in a merely damp crevice. More significant is the taxonomic movement around it: this is the second split within the Iberian rock butterworts in a short span, and further populations in adjoining sierras may yet be revised. Older literature on the Serranía de Cuenca carries these plants under P. mundi.

Where and when to see it

May and June, while winter water is still working through the limestone. Search the north-facing gorges and the headwaters of the streams, at the points where water leaves the wall and the rock shines. Look up: the rosettes often hang above eye level in a crevice or on a tufa lip. Do not step onto the tufa deposits at the foot of the wall — they are soft and brittle and do not grow back. Photograph flower, fruit and leaf and record the locality precisely; for a newly described species a good observation is worth a great deal.

Conservation status

The species has not been assessed for the global Red List, which is hardly surprising for a taxon of 2020; there is therefore no international category, and CITES does not apply. What is known: an Iberian endemic with a small range in one limestone massif, tied to permanently wet faces wholly dependent on spring discharge. The threats follow: the tapping of springs, falling water tables in longer droughts, road and water works through the gorges, and recreational pressure where climbing routes and canyoning run along wet walls. While an assessment is lacking, the empty field says nothing here about safety.

Scientific name

Pinguicula casperiana | Crespo, Martínez-Azorín, Alonso & Sáez, 2020

Described by Manuel B. Crespo, Mario Martínez-Azorín, Miguel Ángel Alonso and Llorenç Sáez in 2020. The type area lies in the Serranía de Cuenca, in the border area of the Spanish provinces of Cuenca and Guadalajara, where the species was long confused with the related Pinguicula mundi and P. dertosensis. The species name casperiana, like P. casperi, honours the German taxonomist Siegfried Jost Casper.

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