Hovering sunbirds in the Old World: occasional behaviour or evolutionary trend?

Abstract

Th e nectarivory of sunbirds in the Old World and hummingbirds in the New World evolved independently. While both groups are specialised in their feeding apparatuses, hummingbirds are moreover famous for their adaptations to sustained hovering fl ight. Recently, an example of a pollination system of the invasive plant Nicotiana glauca has been used to show that less adapted sunbirds also are frequently able to hover. Nevertheless, the question has remained why plants adapted to bird hovering pollination do not occur outside the New World. In this paper we show that the long-peduncle Cameroonian Impatiens sakeriana is not capable of autonomous selfi ng and can be pollinated only by two often hovering sunbirds, the Cameroon sunbird Cyanomitra oritis and the northern double-collared sunbird Cinnyris reichenowi . Our study revealed that this plant is highly specialised for pollination by C. oritis . Cinnyris reichenowi hovers less frequently and often thieves nectar by piercing the fl ower spur when perching. Th is study shows that pollination systems occurring in the Old World follow similar evolutionary trends as systems including hovering hummingbirds in the New World.

Generalization versus Specialization in Pollination Systems: Visitors, Thieves, and Pollinators of Hypoestes aristata (Acanthaceae)

“…In accordance with our observations (Fig. 1), we agree that ‘trait-matching’ between flowers and their visitors plays an important role in pollination interactions [24], [44], [66]–[68].…”

“…Our finding that the two carpenter bees were the only important pollinators among the wide spectrum of floral visitors is in accordance with the bee pollination syndrome of H. aristata and with the concept of pollination syndrome [4], [39]. Nevertheless, as much as successful pollination is highly dependent on ‘trait-matching’ between flowers and their visitors [24], [44], [66]–[68], we agree that the visitor’s body size plays an important role in the assessment of the pollination syndrome validity. The large bees were effective pollinators whereas the relatively smaller bee A. mellifera had a negative effect on H. aristata reproduction.…”

“…In fact, a broad spectrum of diverse floral visitors with positive, neutral, and even negative effects on plant reproductive success can be found [21]–[24]. Several different techniques can be used to test the effects of particular pollinators.…”

The nectar spur is not only a simple specialization for long‐proboscid pollinators

“…There is another common Impatiens species ( I. sakeriana ) in the studied area, and the pollen grains of these two plant species cannot be distinguished. However, we do not expect any bias in the data, since I. sakeriana is pollinated by birds and is not visited by insects (Janeček et al ., , ; Padyšáková & Janeček, ). Pollinator effectiveness, calculated as the rate of pollen deposition (= no.…”

Food selection by avian floral visitors: an important aspect of plant-flower visitor interactions in West Africa

“…f. (Balsaminaceae). According to pollination syndromes (Faegri & van der Pijl, 1979), I. sakeriana can be considered as a typical bird‐pollinated species (see also Janeček et al ., 2011 and Bartoš et al ., 2012), whereas Hypericum revolutum and P. eminii are typical insect‐pollinated species (Janeček et al ., 2007; Bartoš et al ., 2012). The other two species ( L. columnaris and Hypoestes aristata ) have some traits associated with insect pollination and others with bird pollination.…”