Seasonal dynamics of floral composition and flower visitors in a
subtropical alpine ecosystem in Taiwan
Abstract
Flowering phenology of alpine plant communities and seasonal dynamics of
flower visitors have been scarcely studied in the tropical/subtropical
alpine regions. We report flowering phenology, flower production, and
flower-visiting insects in the alpine site of central Taiwan. Throughout
the research period (2017–2018), we recorded flowering phenology of 130
plant species, flower production of 81 species, and 15,127 insects
visiting alpine flowers. Most of the alpine plants were visited by
dipteran insects and/or hymenopteran insects. The seasonal patterns of
flowering were more apparent in bee-visited plants compared to
fly-visited plants in which the flowering of bee-visited plants clearly
increased as the season progressed. About 63% of flower visitors were
dipteran insects (syrphid and non-syrphid flies), and 30% were
hymenopteran insects (mostly bumble-bee workers). Although the seasonal
trend in fly abundance was less clear between years, bumble-bee
abundance consistently increased in the middle to late seasons,
reflecting colony development. There was a positive correlation between
bee abundance and the number of flowering species of bee-visited plants,
but there was no correlation between fly abundance and the number of
flowering species of fly-visited plants throughout the season. These
results suggest that the flowering phenology of subtropical alpine
communities is influenced by the seasonal availability of pollinators.
Bumble bees, syrphid flies, and non-syrphid flies had wide ranges of
foraging flowers, but their niche overlap was relatively small. Because
cold-adapted bumble bees are threatened by climate change in Taiwan,
plant–pollinator interactions may be disturbed by global warming.