Effects of Flowering Mode and Pollinator Sharing on Reproductive Success in Natural Hybrid of Two Epimedium (Berberidaceae) Species

Mediated by pollen flow, natural hybridization is deemed a crucial factor that propels speciation in floral plants. Despite the fact that the diversity of Epimedium species is concentrated mainly in Southwestern China, the potential impact of interspecific pollination on natural hybridization has yet to be empirically scrutinized. To explore this, we studied the flowering period and the visitors of flowers in three frequently overlapping Epimedium species at Jinchengshan National Forest Park, located in Nanchong, Sichuan Province. Additionally, we performed a series of pollination experiments to examine breeding systems and hybrid compatibility. Morphologically, Epimedium pubescens and Epimedium wushanense are clearly distinct and easily recognizable by flower morphology, while the putative hybrid is morphologically intermediate between them. Our observation revealed that E. pubescens and E. wushanense had 15 days of overlapping anthesis. Both species are self-incompatible and require pollinator services for successful reproduction. Although their pollinators differ in quantity and species, Lasioglossum sp. (Hymenoptera: Halictidae) visited all three species. Artificial pollination revealed no breeding barriers among the three species, and the resulting hybrid seeds exhibited fertility. The overlapping time of flowering, common floral visitors, and compatibility of hybrids may be important factors contributing to successful interspecific pollination and speciation for natural hybrid species of E. pubescens and E. wushanense. Consequently, the role of potential interspecific pollination is crucial for hybrid speciation and the evolutionary dynamics of Epimedium species.