Outcrossing syndrome in alpine plants: Implications for flowering phenology and pollination success

Abstract

AbstractThis study aims to clarify the community‐wide mating systems and pollination success of alpine plants. Selfing abilities and fruit‐set success of entomophilous alpine plants were compared using a dataset of 46 species that were obtained during the last 30 years in the Taisetsu Mountains, northern Japan. Almost all species showed self‐incompatibility or weak self‐compatibility, indicating that obligate outcrossing is a common mating system in alpine plants. This mating property leads to a clear seasonal pattern of fruit‐set success responding to the seasonal dynamics of pollinator activity. Most species are visited by bumble bees and/or flies, and the seasonal trend of pollination success was shown to vary among pollinator types. Pollen limitation in bee‐pollinated plants was intense early in the season and tended to decrease as the season progressed, reflecting the colony development cycle of bumble bees. Thus, the fruit‐set success of bee‐pollinated plants increased with the delay of flowering time. In contrast, seasonal trends in the pollen limitation and fruit‐set success of fly‐pollinated species were less clear. Mixed‐type plants visited by both bees and flies showed a pattern intermediate to that of bee‐type and fly‐type plants. The flowering phenology of alpine plant communities was greatly regulated by snowmelt patterns, and the pollination success of single species varied greatly among local populations distributed in different snowmelt habitats. These heterogeneous landscape features create diverse plant–pollinator interactions in alpine ecosystems. Based on these results, the ecological and evolutionary significance of the outcrossing syndrome in alpine plants is discussed.