Tropicos | Name - Lapeirousia arenicola Schltr.

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Iridaceae in sub-Saharan Africa

African Iridaceae > Iridaceae > Lapeirousia > Lapeirousia arenicola

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Lapeirousia arenicola Schltr.

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Project Name Data (Last Modified On 6/6/2016)

Acceptance : Accepted

Taxon Profile (Last Modified On 6/17/2016)

Description: Plants 100–120 (–150) mm high, often ± tufted. Corm bell-shaped, 35–50 mm below ground, ± 6 mm diam.; tunics red-brown, smooth, basal rim lightly serrated, teeth directed downward. Stem usually branched, mainly at base, compressed and 2-angled, angles often weakly winged and slightly serrated, normally without cormlets at below ground nodes. Leaves 3–6(–many), lowermost usually conspicuously longer than others, linear, ascending to falcate, 2–3 mm wide, strongly ribbed, upper cauline leaves shorter, usually resembling bracts and not or barely ribbed, usually subtending branches. Inflorescences 2–6-flowered spikes, lax or crowded; outer bracts green, leaf-like, 15–25 mm long, lanceolate, acute, keeled throughout or at least distally, unifacial apically for 3–5 mm, keels often red, minutely serrated, margins hyaline, inner bract transparent with two green keels, 1/2 to 2/3 as long as outer, forked at tip. Flower zygomorphic, cream to biscuit-pink, lower tepals each with red mark near base; perianth tube 15–25(–33) mm long, cylindric, curving slightly outward at apex; tepals subequal or dorsal slightly larger, lanceolate and acute or obtuse, 8–11 × 3–4 mm, usually spreading ± horizontally when fully open, all in same plane. Stamens unilateral, erect; filaments ± 7 mm long, exserted ± 3.5 mm from tube; anthers contiguous, 1.5–2.5 mm long, violet, pollen mauve. Style dividing opposite upper half of anthers, style branches ± 1.5 mm long, divided for ± half their length. Capsules oblong, (8–)10–12 × ± 6 mm, apices of locules forming auriculate lobes decurrent on wing-like locular ridges in upper half. Seeds globose, flattened at chalazal end, ± 1.4 mm diam., dark shiny brown. Chromosome number 2n = 16. Flowering time: August to September, occasionally in early October.

Country: South Africa

South African Province: Northern Cape, Western Cape

Distribution and ecology: restricted to the South African Atlantic coast and near interior, extending from near Vanrhynsdorp and Vredendal in Western Cape northward through the sandveld and low coastal hills of Namaqualand as far north as the Anenous flats at the southern edge of the Richtersveld in Northern Cape; in deep sandy soils, especially the rather fine-grained red-tinged sands of lowland and coastal Namaqualand.

Diagnosis: low-growing and typically a small plant, Lapeirousia arenicola can readily be distinguished by its small size, pale pinkish-beige, slender-tubed flowers and narrow tepals. Perhaps most easily confused with L. macrospatha which has similarly coloured flowers, L. arenicola has a uniformly narrow, cylindric perianth tube 17–33 mm long and tepals 10–11 × 3–4 mm whereas L. macrospatha has a wider tube, 25–35 mm long, expanded toward the apex and considerably larger tepals, the uppermost largest and ± 20 × 7 mm. Although the two species appear similar on casual examination, they are quite distinct and do not intergrade although their ranges overlap slightly. Both have been found growing together just north of the Port Nolloth road below Anenous Pass. Perianth tube length may coincide but the tepals of L. arenicola are always smaller and the tube more often than not is substantially shorter than in L. macrospatha. The two species are closely related and have been shown to be immediately related in molecular phylogenetic studies.

General Notes: although Lapeirousia arenicola bears a superficial resemblance to the Western Cape L. anceps in flower colour and in the narrowly cylindric perianth tube these similarities are evidently due to convergence. The molecular phylogeny shows them to be distantly related. More puzzling is the striking resemblance between L. arenicola and L. simulans, which co-occur at several sites along the west coast, where their nearly identical flowers make a strong impression. Vegetatively, L. arenicola is always more compact in habit and often has a somewhat shorter perianth tube, so that they can be distinguished when seen growing side by side. More significant differences are underground: the corms of L. arenicola lie 35–50 mm below the surface and the underground part of the stem rarely produces cormlets whereas corms of L. simulans are usually 60–80 mm below ground and always have a fairly large cormlet at each of two underground nodes. L. arenicola self-compatible but probably facultatively outcrossing early in the flowering season when plants produce fairly large, long-tubed flower with stronger colouring that later in the season. Toward the end of the flowering season the flowers of some populations have weakly contrasting markings, are smaller, and have a perianth tube 15–18 mm long (compared with ± 25 mm on the same plants earlier in the season). These late-blooming flowers are primarily autogamous..