Hyobanche hanekomii (Orobanchaceae) is pollinated by non-flying mammals and birds

Abstract

H. hanekomii was recently described as a new member of the genus Hyobanche inside the Orobanchaceae family. H. hanekomii is a small geoflorous holoparasitic plant, which often grows under shrubs and has red-flowered inflorescences, which do not emit a scent. The plant combines characteristics from bird- and mammal-pollinated plants. Until now it was uncertain if H. hanekomii is pollinated by birds or by non-flying mammals, since the species is showing an intermediate morphology when compared to H. atropurpurea (mammal pollinated) and H. sanguinea (bird pollinated). Elephantulus edwardii and Nectarinia famosa were observed foraging on H. hanekomii inflorescences indicating a mixed pollination syndrome or a transmission state between bird pollination to pollination by non-flying mammal. In this study I prove that E. edwardii and N. famosa are indeed pollinators of H. hanekomii. This was done by observing the interaction between different animal species and H. hanekomii inflorescences in their natural habitat by using camera traps and camcorders. It could be observed that E. edwardii licked nectar from flowers of H. hanekomii with its long tongue. The animals pressed their rostra deep into the flowers. While foraging on the flowers, it could be observed that pollen was placed onto the rostra of the animals. It was also observed, that the stigma of the flower touched the animals on the same spots where pollen was placed. To drink on the flowers, Nectarinia famosa inserted its beak into the flowers. While doing so, it was observed that pollen was placed on the beaks and that the stigma touched the animals. It is possible that both species transport pollen from one H. hanekomii flower to another while foraging on them, and that the pollen reaches the stigma of another flower. Because of this both species are considered as pollinators of H. hanekomii. E. edwardii was identified as the main pollinator of H. hanekomii as they visit the inflorescences frequently. N. famosa was detected as a secondary pollinator of H. hanekomii as they visit the flowers infrequently. This issue has to be examined further since the rarity of N. famosa visits could be influenced by different factors like removal of perching positions around the plants to have a better camera angel or by the cameras itself, so that N. famosa would visit the H. hanekomii inflorescences more often in an non altered surrounding. In addition UV photography and spectrometry revealed that no UV reflecting areas are present on the plants indicating adaption to non-flying mammal than bird pollination syndrome. The same counts for missing stinging hairs on the flowers. In contrary some of the important flower characteristics (Flower entrance width and height) are significant smaller than those of the non-flying mammal pollinated plant H. atropurpurea indicating a bird pollination syndrome.