Pollination Biology of Hydnora africana Thunb. (Hydnoraceae) in Namibia: Brood‐Site Mimicry with Insect Imprisonment

Abstract

Hydtiora africana is a root holoparasite of southern Africa that emerges only to flovi'er. The trimerous flowers of H. africana have androecial and gynoecial chambers and attract fioral visitors with putrid odors emitted from prominent osmophores. We observed floral phenology and insect visitation for H. africana at two sites in southern Namibia and evaluated the insect imprisonment mechanism with beetle addition and pollen viability assays. Flowers are putatively protogynous for 3 d. We observed 18 Horal visitors, including 10 coleopteran species imprisoned by the smooth inner surface of the androecial chamber. The hide beetle Dermestes nuutilatiis (Tenebrionidae) accounted for 76.9% of tbe imprisoned insects, with a density of 2.2 ± 0.6 per flower. The D. maculatiis addition experiment {n = 9) clearly demonstrated imprisonment during the carpellate stage. Changes in the inner surfaces of the androecial chamber, stippling, and texturing allowed D. maculatus to escape after pollen release. More than 55.5% of tbe beetles escaped, dusted with pollen, within 3 d after pollen release. Pollen was still viable 3 d after pollen release. The beetle addition and pollen assays demonstrate the efficiency of the H. africana imprisonment mechanism.

Developmental origins of the world’s largest flowers, Rafflesiaceae

“…A similar example has been documented in two related groups, Aristolochia and Hydnora, which have evolved floral chambers with different construction. In Hydnora, the roof of the chamber is formed by the stamens; in Aristolochia it is formed by the perianth (29,34). A second model would be that the common ancestor of Rafflesiaceae possessed a floral chamber similar to that in Sapria [i.e., derived from expansion between the ring and the column (Fig.…”

Spatial and temporal variation in volatile composition suggests olfactory division of labor within the trap flowers of Aristolochia gigantea

“…Finally, the larger Aristolochiaceae, which now includes the former Piperaceae, Saururaceae and Hydnoraceae (APG, 2016), includes additional pollinator niches, including fungal mimicry in the ground-blooming genus Asarum and the cauliflorous Aristolochia arborea (Kaiser, 2006;Sinn et al, 2015;Vogel, 1978). The fetid, fleshy flowers of Hydnora africana, a root parasitic species, emit sulfur volatiles (Burger et al, 1988) and form subterranean chambers that trap tenebrionid beetles in southern Africa, suggesting a rotting-hide niche (Bolin et al, 2009).…”

The Importance of Oligosulfides in the Attraction of Fly Pollinators to the Brood-Site Deceptive SpeciesJaborosa rotacea(Solanaceae)

“…The partially buried carrion-mimicking flowers of the South African parasitic plant Hydnora africana (Hydnoraceae) emit oligosulfides (Burger et al 1988), and whereas they are primarily visited by blowflies in South Africa, across the border in Namibia they are pollinated by Dermestes beetles (Dermestidae) that feed on dead animals (Bolin et al 2009). In the tropical rainforests of Central America, oligosulfides (or similar S-volatiles) are the primary attractants in a guild of nightblooming flowers that are pollinated by glossophagine bats (von Helversen et al 2000), while daytime blooming Aristolochia species appear to use the same volatile compounds to attract saprophilous flies as pollinators (Blanco 2002).…”