Dimerocostus O. Kuntze
Type: Dimerocostus strobilaceus
Plants gigantic rhizomatous unbranched perennial herbs, stem very stout and somewhat spiral, comprised of leafless sheaths. Leaves spiral with ligulate sheaths, often congested near the tip of the elongate stem, oblong-oblanceolate, narrowly acuminate at the apex, cuneate to rounded at the base. Ligule very short or absent. Inflorescence cylindrical, spirally contorted, scarcely cone-like as in Costus. Bracts green to yellow-green, coriaceous, often sheathing, ovate, sometimes with deltate foliaceous appendage, much shorter than flowers. Bractole tubular, bicarinate. Calyx large, tubular, 3-parted with unequal lobes, often exceeding bracts. Corolla 3-lobed, white or light yellow. Labellum large and showy, white or yellow, if white then often with yellow spot at center. Stamen petaloid, tip reflexed, anthers attached at center. Pollen grains large, dicolpate or mixed colpate-porate. Stigma cup-shaped. Ovary bilocular, ovules biseriate. Fruit a capsule, tardily dehiscent or non-dehiscent, only slightly fleshy. Seeds glossy black, with small cushion-like white aril. Floral parts with red-brown punctations.
Dimerocostus is found in Central and South America from Nicaragua in the north to northern Bolivia in the south, mostly following the eastern slope of the Andes and the inland Caribbean coast into Venezuela and Suriname. Dimerocostus argenteus is restricted in distribution to Peru and Bolivia, overlapping in range with Dimerocostus strobilaceus subsp. gutierrezii.
Phylogeny and Classification:
Dimerocostus forms a clade sister to Monocostus. Together, these two new world genera are sister to Chamaecostus.
According to Maas in his Flora Neotropica Monograph, there are two recognized species of Dimerocostus (D. stroblilaceus and D. argenteus), with D. strobilaceus comprised of three subspecies:
D. strobilaceus subsp appendiculatus
D. strobilaceus subsp strobilaceus
D. strobilaceus subsp gutierrezii
Ecology and Pollination Biology:
Populations are mostly found in wet forests and along streambeds from sea-level to 500 meters with few populations reaching 1800 meters. Beetles of the family Cicyndelidae have been noted to visit flowering Dimerocostus plants and enter into the labellum, but effective pollination has not been assessed. Bees and flies also frequent fresh flowers of Dimerocostus.
Common Names, Uses and Notes:
Nigel Smith (University of Florida, Department of Geography) notes that Peruvian children eat the arils. The plant is known as "Situlle" in the Pacaya-Samiria region of Peru and as "Saguiro" in the San Martin region of Peru.
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