Abstract:

The discontinuous distribution between alkaline limestone soil with high calcium content and acidic red soil with low calcium content is characteristic of karst areas, and strongly affects plant species composition in natural communities. Whether the soil types affect plant reproductive success, however, remains unknown. Two populations of Corydalis sheareri, a species commonly occurring in alkaline limestone soil and acidic red soil, were investigated. The soil properties of the two habitats were examined, and flowering phenology, floral traits, floral visitor types and their behavior, breeding system and reproductive success were compared. Organic matter, total nitrogen, total calcium, and pH value were higher in the limestone soil, while soil moisture content was lower than that found in the red soil. Floral longevity was not significantly different between plants from the two habitats. However, plants found in the limestone soil were shorter in height and bloomed one week later with a shorter flowering period (4 weeks) than those found in the red soil (6 weeks). Floral traits (inflorescence size, flower length, opening size, spur length and stigma diameter) were not significantly different between the two habitats. Corydalis sheareri was obligately xenogamous, with sexual reproduction dependent on insect pollinators. The major floral visitor was Anthophora melanognatha, a long-tongued nectar collecting bee. Bee visit frequency and seed set per flower were not significantly different between the two habitats, but fruit set per plant in the limestone soil was significantly lower. Our results indicated that, no difference in the seed set could be explained by similar pollinator abundance, while the differences of flowering phenology and fruit set could be caused by differences in the soil properties between the two habitats.

Key words: Corydalis sheareri, soil property, flowering phenology, breeding system, fruit set, seed set, reproductive success