The pollination ecology of Rhododendron floccigerum Franchet (Ericaceae) in Weixi, Yunnan Province, China

Abstract

Identifying the pollinators of Rhododendron species is of great interest due to potential conservation threats in the native range of the genus, but the pollinators of species in Rhododendron subgenus Hymenanthes section Pontica subsection Neriiflora are unknown. Bees (Hymenoptera; family Apidae) are thought to be the pollinators of many Rhododendron species; however, species in subsection Neriiflora have ornithophilous floral morphology. We studied R. floccigerum (subsection Neriiflora) to determine the identities of visiting, potentially pollinating, and robbing species through in-person and time lapsed camera trap observations. We compared floral morphological characteristics of R. floccigerum with visitor morphological measurements to determine if visitors could fit inside the corolla. Thirteen species were observed visiting R. floccigerum (two insects, two mammals, and nine birds) and this study provides the first empirical evidence of both bird and mammal visitors to Rhododendron species. We determined that the following species are potential pollinators: Bombus sp. (an insect genus), Aethopyga gouldiae, Garrulax affinis, Heterophasia melanoleuca, and Yuhina diademata (all bird species), and we suspect that Apis sp. (an insect genus), Dremomys pernyi, Tamiops swinhoei (two mammal species), Minla ignotincta, M. strigula, Parus major, and Phylloscopus affinis (four bird species) likely rob R. floccigerum. All visitors were able to fit their heads/bodies into the corolla. We also found that though predation is frequent, the number of robbers and variety of robbing methods is unlikely to contribute to floral morphological evolution or speciation. Further understanding of the pollination biology of species in subgenus Hymenanthes will allow for effective conservation.