Flowering Phenology and Anthophilous Insect Community in a Grassland Ecosystem at Mt. Yufu, Western Japan

Abstract

The hillsides of Mt. Yufu, located in Kyusyu, Japan, is a dormant volcano, are covered with natural and semi-natural grasslands; the latter of which are maintained by traditional mowing and burning. Both the natural and semi-natural grasslands are inhabited by many grassland-specific plant species, some of which are now endangered in Japan. To understand pollination mutualisms in the grassland ecosystem, we investigated the flowering phenology and anthophilous insect communities on 149 plant species from 49 different plant families, from April to October 2001. In total, 1192 individuals from 308 species, 83 families and 10 orders of Insecta were observed on flowers of 101 plant species. The most abundant insect order was Hymenoptera (37.8% of individuals), followed by Diptera (32.5%), Coleoptera (22.7%) and Lepidoptera (6.2%). The proportions of Coleoptera and Lepidoptera were respectively smaller and greater than in forested habitats, suggesting that many anthophilous beetles depend on woody plants during their larval stages and that anthophilous butterflies (especially Nymphalidae) are associated with grassland-specific perennials (especially Viola spp.) in their larval stages. The bee fauna consisted of 54 species, from 10 genera and 6 families; the bee community was characterized by an absence of cavity-nesting Hylaeus and Xylocopa and by the predominance of long-tongued Tetralonia in the early spring. The bumblebee community was characterized by the predominance of a shorthaired Bombus ignitus, uncommon in forested habitats. The dominant pollination syndrome, among 70 plant species for which pollinators were inferred, was melittophily (82%), followed by myophily (14%), psychophily (1.4%), phalaenophily (1.4%) and anemophily (1.4%). Among the melittophilous species, small-bee-pollinated species (45%) dominated, followed by Bombus- (36%), Apis- (8.6%), Tetralonia- (6.9%), megachilid- (1.7%) and wasp- (1.7%) pollinated species. These data on community-level plant-pollinator interactions at Mt. Yufu will contribute to the conservation of endangered grassland ecosystems.