@article {22676, title = {Hawkmoth pollination of aerangoid orchids in Kenya, with special reference to nectar sugar concentration gradients in the floral spurs}, journal = {American Journal of Botany}, volume = {94}, year = {2007}, pages = {650-659}, chapter = {650}, abstract = {

\"The African orchid flora has a high proportion of species with long-spurred white flowers. Few data exist to test the prediction that this floral syndrome pattern reflects an important role for hawkmoth pollination in the evolution and ecology of these orchids. The pollination biology of five aerangoid orchid species (Rangaeris amaniensis, Aerangis brachycarpa, A. confusa, A. thomsonii, and A. kotschyana) was investigated in Kenya. Four of these have long spurs (.10 cm) and were pollinated by Agrius convolvuli and Coelonia fulvinotata. Aerangis confusa, which has relatively short spurs (ca. 4 cm), was pollinated by the short-tongued hawkmoths Hippotion celerio and Daphnis nerii. Nectar frequently filled the entire spur in some of the study species, even at anthesis. Sugar concentration of the nectar of four species was found to vary from ca. 1\% at the mouth of the spur to 20\% at the tip. Gradients were expressed more strongly in species with long, straight spurs. Species with spirally twisted spurs showed both steep and shallow nectar gradients. These gradients, previously unknown in plants, may function as a \‘\‘sugar trail,\’\’ enticing long-tongued hawkmoths to probe deeply into spurs without incurring the cost of filling an entire spur with concentrated nectar. In addition, the most concentrated nectar is kept out of reach of short-tongued pollinators.\"

}, keywords = {AERANGIS, AGRIUS, COELONIA, DAPHNIS, FLORAL MORPHOLOGY, FLORAL SCENT, HIPPOTION, KENYA, NECTAR COMPOSITION, ORCHIDACEAE, POLLINATION, POLLINATOR SPECIFICITY, RANGAERIS, SPHINGIDAE}, author = {Martins, D.J. and Johnson, S.D.} } @article {22675, title = {Pollination of the long-spurred African terrestrial orchid Bonatea steudneri by long-tongued hawkmoths, notably Xanthopan morganii}, journal = {Plant Systematics and Evolution}, volume = {305}, year = {2019}, month = {08/2019}, pages = {765-775}, chapter = {765}, abstract = {

\"Charles Darwin correctly predicted the existence of an extraordinarily long-tongued hawkmoth in Madagascar, based on the length of the floral spur of an Angraecum orchid. This hawkmoth, Xanthopan morganii, is also the longest-tongued hawkmoth on the African mainland, but its ecological role as a pollinator has been virtually unknown outside of Madagascar. We investigated whether X. morganii pollinates Bonatea steudneri, an orchid with floral spurs that vary from 10 to 21 cm in length among populations. At a forest locality in central Kenya, we observed X. morganii individuals with tongues ca. 16 cm in length pollinating B. steudneri plants with spurs ca. 15 cm in length. At other localities in Kenya, we observed visits by the hawkmoths Agrius convolvuli (tongue c. 12 cm) and Coelonia fulvinotata (tongue ca. 10 cm). Pollinaria of B. steudneri are attached to the eyes of hawkmoth visitors. Flowers of B. steudneri show several adaptations for hawkmoth pollination, including anthesis at dusk and nocturnal emission of scent dominated by the volatile compound linalool. This study highlights the potential for predicting certain highly specialized interactions among species by matching of their respective morphological dimensions.\"

}, keywords = {AGRIUS, ANGRAECUM, BONATEA, COELONIA, COEVOLUTION, FLORAL SCENT, KENYA, ORCHIDACEAE, POLLINATION, POLLINATOR SPECIFICITY, SPHINGIDAE, XANTHOPAN}, doi = {10.1007/s00606-019-01605-2}, url = {https://doi.org/10.1007/s00606-019-01605-2}, author = {Balducci, M.G. and Martins, D.J. and Johnson, S.D.} } @article {21089, title = {The long-tongued hawkmoth pollinator niche for native and invasive plants in Africa}, journal = {Annals of Botany}, volume = {117}, year = {2016}, pages = {25-36}, chapter = {25}, abstract = {

\"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.\"

}, keywords = {BIOGEOGRAPHY, COELONIA, ECOLOGY, FLOWER COLOUR, INVASIVE SPECIES, NECTAR COMPOSITION, NEPHELE, POLLINATION, POLLINATOR SHIFT, POLLINATOR SPECIFICITY, PROBOSCIS, SOUTH AFRICA, SPHINGIDAE, WORLDMAP1}, doi = {10.1093/aob/mcv137}, author = {Johnson, S.D. and Raguso, R.A.} } @article {19224, title = {Orchid pollination: from Darwin to the present day}, journal = {Botanical Journal of the Linnean Society of London}, volume = {161}, year = {2009}, month = {09/2009}, pages = {1-19}, chapter = {1}, abstract = {

\"In this year celebrating the bicentenary of the birth of Darwin and the sesquicentennial of the publication of Darwin\&$\#$39;s On the Origin of Species, the present paper aims to assess the impact of Darwin\&$\#$39;s legacy on the history of orchid pollination biology. To illustrate the major contribution of Darwin to this fascinating biological field, we focus on the large angraecoid orchid group and propose an overview of the complex relationships that these orchids have developed with specific pollinators. We further discuss how Darwin\&$\#$39;s seminal work on the angraecoid orchid Angraecum sesquipedale triggered the beginning of a long debate about the evolution of long floral spurs and why his idea of reciprocal evolution or \‘coevolution\’ was one of the great contributions to evolutionary biology.\"

}, keywords = {AGRIUS, ANGRAECUM, BIRDS, COELONIA, DAPHNIS, DARWIN, HIPPOTION, MADAGASCAR, MASCARENE ISLANDS, NEPHELE, ORCHIDACEAE, PANOGENA, POLLINATION, POLLINATOR SHIFT, POLLINATOR SPECIFICITY, REVIEW, SPHINGIDAE, XANTHOPAN}, doi = {10.1111/j.1095-8339.2009.00995.x}, url = {https://academic.oup.com/botlinnean/article/161/1/1/2418453}, author = {Micheneau, C. and Johnson, S.D. and Fay, M.F.} }