Pollination by the Japanese White-eye Zosterops japonicas (Zosteropidae) in Pentacoelium bontioides (Scrophulariaceae)

Abstract

Pentacoelium bontioides Siebold & Zucc. (Scrophulariaceae) is generally regarded as an entomophilous species. However, it was observed in our preliminary observation that nectarivorous birds frequently visited the flowers of P. bontioides. To determine whether the species is actually pollinated by the nectarivorous birds, we observed flower visitors and their behaviors using digital video camera in a natural population of the species. The Japanese white-eye Zosterops japonicus Temminck & Schlegel (Zosteropidae) visited the flowers for supping nectar at daytime, and its head and neck closely contacted with the anthers and stigma of P. bontioides. The nectar volumes secreted from the flowers of P. bontioides are greater than those of the entomophilous species and comparable with those of other ornithophilous species. These facts suggest that the Japanese white-eye actually plays as an important role as pollinator of P. bontioides. Although plant species pollinated by nectarivorous birds are rarely reported in East Asia, P. bontioides appears to be an ornithophilous species adapted for pollination by the Japanese white-eye.