Bird pollination in an African Satyrium (Orchidaceae) confirmed by camera traps and selective exclusion experiments

Abstract

Motion-activated cameras (“camera traps”) are useful for recording plant–animal interactions that are difficult to observe using conventional means. We used camera traps to document interactions between animal flower visitors and the orchid Satyrium neglectum subsp. woodii and used mesh exclosures which selectively exclude access of larger animals to flowers to test the importance of bird visits for pollination. Camera footage revealed that the orchid is visited by two sunbird species (amethyst and greater double-collared) which carry pollinaria on the upper mandible of their beaks. Plants which could only be accessed by bees and other small insects had few pollinaria removed and set very few fruits relative to plants which could also be accessed by larger animals such as sunbirds. The sturdy inflorescence stem, and thick fleshy perianth tissue, orange–red colour of the flowers, low scent production and large viscidia, are traits shared with other, distantly related bird-pollinated Satyrium species and can therefore be considered likely to play a functional role in bird pollination. We previously made anecdotal observations of sunbird visits to this orchid species in south-central Africa, and this study conducted in populations in South Africa confirms that sunbird pollination is consistent across the highly disjunct distribution of the taxon.