Abstract: While early flowering is generally favored by natural selection in plants, alpine species may risk pollination failure with advanced blooming, making selfing an effective reproductive strategy under pollen limitation. Thus, pollination variability during flowering could drive seasonal mating-system shifts, though this hypothesis awaits verification. We investigated Primula atrodentata, a distylous plant species with long flowering duration in southeastern Tibet, by conducting pollinator observations, floral trait measurements and pollination manipulation experiments across different flowering periods in three populations to examine temporal variation in reproductive success and mating system responses. Our results reveal nonlinear elevational patterns in pollinator visitation and selfing syndrome, with early-flowering individuals showing reduced pollinator interactions (leading to stronger pollen limitation and lower reproductive success) but enhanced selfing adaptations. Notably, self-incompatibility index correlated significantly with both pollinator visitation and selfing syndrome expression. This study represents a first step toward systematically investigating the seasonal shifts in mating system caused by phenological asynchrony. Expanding such research will be crucial for understanding plant adaptations to pollinator mismatch—a growing challenge driven by climate changes.

Key words: alpine plant, breeding system, flowering phenology, herkogamy, pollen limitation, self-compatibility