Abstract
Floral syndromes are traditionally thought to be associated with particular pollinator groups. Ornithophilous flowers tend to have traits that facilitate bird pollination such as having long, narrow, tubular corollas, often vivid coloration and diluted, sucrose-rich nectar. However, recent studies have shown that flowers attract a broader spectrum of visitors than might be expected. Furthermore, the classification of floral visitors as ‘robbers’ or ‘pollinators’ often is not as simple as it seems, as pollinators can at times act as robbers and vice versa. We studied the species composition, behaviour and ecology of floral visitors, including potential pollinators and robbers, of Heliconia angusta (Heliconiaceae), an endemic understory herb of the Atlantic Rainforest of Brazil. In addition, the impact of the plant inflorescence attractiveness and of weather and light conditions on visitor abundance and frequency was investigated.Flower visitors were found to be scarce with a total of only 151 visits being observed during 120 h of field observations. A stingless bee species (Trigona sp.) appeared to be the most abundant visitor to the ornithophilous flowers of H. angusta, along with four different species of hummingbirds and two species of butterflies. We consider Trigona sp. rather as pollen robber, but which still has the potential to be a secondary pollinator, whereas the hummingbirds were the principle legitimate visitors. Most flower visitors were recorded between 9.00 am and 1.00 pm with a higher number visiting under semi-shaded conditions than in full shade. Hummingbird numbers increased with flower abundance while the other visitor group numbers were not affected.
Highlights
Tropical flowering plants depend overwhelmingly on animals as vectors of pollen transfer
The most frequent visitor to H. angusta was Trigona sp., a small black stingless bee (Hymenoptera, Apidae, Apinae, Meliponini), which accounted for 54 % of all visits and collected only pollen
Four different species of nectar feeding hummingbirds accounted for 40 % of all visits, of which two species of traplining hermits (Phaethornis ruber and Phaethornis squalidus) visited H. angusta most frequently
Summary
Tropical flowering plants depend overwhelmingly on animals as vectors of pollen transfer. Despite the great variety of plant-pollinator systems, it is possible to associate floral traits with particular pollinator groups as a series of pollination syndromes Ornithophilous flowers tend to have traits that facilitate bird pollination (Smith et al 1996), such as long, narrow, tubular corollas and often vivid coloration (Willmott & Burquez 1996). Neotropical Heliconia species (Heliconiaceae) are associated with “bird-flower” pollination syndromes in respect to their long, white, tubular flowers and intensive red coloured bracts, attributes which may otherwise infer that they have no other types of visitors (Stiles 1975). The pollination syndrome concept has recently been criticized with researchers finding that flowers often attract a broader spectrum of visitors than that predicted from their respective syndromes (Fenster et al 2004; Dias da Cruz 2006; Ollerton et al 2009; Schmid et al 2011) and that
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