"Background and Aims Unrelated organisms that share similar niches often exhibit patterns of convergent evolution
in functional traits. Based on bimodal distributions of hawkmoth tongue lengths and tubular white flowers in
Africa, this study hypothesized that long-tongued hawkmoths comprise a pollination niche (ecological opportunity)
that is distinct from that of shorter-tongued hawkmoths.
Methods Field observations, light trapping, camera surveillance and pollen load analysis were used to identify
pollinators of plant species with very long-tubed (>8 cm) flowers. The nectar properties and spectral reflectance of
these flowers were also measured. The frequency distributions of proboscis length for all captured hawkmoths and
floral tube length for a representative sample of night-blooming plant species were determined. The geographical
distributions of both native and introduced plant species with very long floral tubes were mapped.
Key Results The convolvulus hawkmoth Agrius convolvuli is identified as the most important pollinator of
African plants with very long-tubed flowers. Plants pollinated by this hawkmoth species tend to have a very long
(approx. 10 cm) and narrow flower tube or spur, white flowers and large volumes of dilute nectar. It is estimated
that >70 grassland and savanna plant species in Africa belong to the Agrius pollination guild. In South Africa, at
least 23 native species have very long floral tubes, and pollination by A. convolvuli or, rarely, by the closely related
hawkmoth Coelonia fulvinotata, has been confirmed for 11 of these species. The guild is strikingly absent from the
species-rich Cape floral region and now includes at least four non-native invasive species with long-tubed flowers
that are pre-adapted for pollination by A. convolvuli.
Conclusions This study highlights the value of a niche perspective on pollination, which provides a framework
for making predictions about the ecological importance of keystone pollinators, and for understanding patterns of
convergent evolution and the role of floral traits in plant colonization."