Endangered Plant of the Month

It's the last Saturday of the month and that means my essay on some rare and endangered plant has to be posted to the Native Plants of NM Facebook group.  Fortunately, I'm ahead of the game and I've got Viola calcicola written up and scheduled to auomatically appear this Saturday morning.  

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Viola calcicola R.A. McCauley & H.E. Ballard

This month I'm looking to describe a rare plant that might actually be in bloom right now. Depending on how warm the spring turns out, this little (and I do mean little) jewel of a violet could be in flower right now down in the Guadalupe Mountains.

The species was described just in 2013 by Ross A. Mccauley of Fort Lewis College and Harvey E. Ballard, Jr. of Ohio University. Our species of interest today is removed by many hundreds of kilometers from any likely relatives and is the second endemic violet found in the Guadalupe Mountain region.

Description (as always, from NM Rare Plants): Acaulescent (having no obvious stem) perennial herb from a short (ca 2.5 cm, 1 inch) vertical rhizome bearing stout fibrous roots; leaves all unlobed or rarely shallowly trilobate; petioles of longest leaves 3-7 cm; leaf blades cordate, triangular-cordate to deltoid with rounded-serrate margins, glabrous; chasmogamous flowers solitary on peduncles generally borne at or slightly above the leaf blades; sepals variable, ovate to lanceolate, the lowest 3-5 mm long and 1-2 mm wide; corolla 0.8-1.5 cm long; petals on different plants varying from nearly white (faintly flushed with violet) to medium purple, lateral petals having few inconspicuous purple veins, spurred petal with prominent and extensive nectar guides, lateral and upper petals narrowly obovate, spurred petal obovate with long-tapering base, 10-13(-15) mm long including spur, 3-5 mm wide, broadly obtuse to rounded at apex; spurred and upper petals glabrous within, lower lateral petal sparsely bearded with few to several clavate or knob-shaped hairs; cleistogamous (non-opening, self-pollinating) flower buds to 3 mm long on peduncles shorter than the leaves; fruit a glabrous capsule. Flowering April to May.

There are no other Viola species with purple flowers in the Guadalupe Mountains. The adjacent Sacramento Mountains have Viola nephrophylla, which has purple petals, but is quickly distinguished by some pubescence on its petal spur.

Violets are the largest genus of cleistogamous plants, forming flower buds that don't open and self-pollinate. Self-pollination works well when you can't find a partner for sexual reproduction, but it limits variability, which can lead to evolutionary dead ends. Fortunately, our violet also produces chasmogamous (open pollinated) flowers. Because these plants live in adverse habitats, cleistogamy may be a way of guaranteeing seed set even if the population size is small and there are no conspecifics nearby.

Distribution: Eddy and Otero counties in NM and Culberson County across the border in TX. The plant favors escarpments and deep canyons on the eastern slope of the Guadalupe Mountains where it finds suitable cracks in Permian age limestone in riparian woodland and montane scrub up to pinyon-juniper woodland, usually on north-facing cliff faces or near spring seeps. 1,525 m (5,000 ft) to 2,135 m (7,000 ft).

Viola calcicola is one of a suite of chasmophilous ( thriving or dwelling in rock crevices, chinks, fissures, crannies, and chasms) plants endemic to the limestone cliffs of the Guadalupe Mountains and adjacent sky-island ranges. In New Mexico it is sympatric with the rare Aquilegia chaplinei, Hedeoma apiculata, Perityle quinqueflora, Polyglala rimulicola, Salvia summa, Nama xylopodum, Chaetopappa hersheyi, and Valeriana texana. Do you notice a pattern?