Long-distance pollen dispersal ensures genetic connectivity of the low-density tree species, Eurycorymbus cavaleriei, in a fragmented karst forest landscape

摘要

Karst forest in southwest China represents one of the world's most spectacular examples of tropical-subtropical karst landscapes and harbours high floristic richness and endemism. Many plant species tend to occur in naturally isolated patches due to the edaphic and topographic heterogeneity and are suffering an increasing stress of habitat deterioration due to both extensive human activities and global climate change in the area. Here Eurycorymbus cavaleriei was selected as a representative insect-pollinated plant species with low density to assess the pollen dispersal and mating patterns of such limestone associated trees. Paternity analysis revealed substantial long-distance pollination events, with a high level of pollen immigration (27.9-41.9 %) from outside the study sites over distance of at least 4,000 m. Pollen dispersal best fits an exponential power model with a fat-tailed (b1) feature and the average pollen dispersal distance was over 2,000 m inferred by the TWOGENER analysis. Despite the dioecious nature, a small amount of biparental inbreeding and moderate correlated paternity were detected based on the multilocus mating system analysis. Relatively few pollen donors (Nep = 3.5-7.0) and substantial variance in male reproductive success (21-24 % of males were responsible for 52-58 % of pollinations) were detected. These results have important implications for the genetic conservation and management of E. cavaleriei. Extensive pollen dispersal provides evidence for substantial intraand/ or inter-patch pollinator movement, which seems promising for E. cavaleriei and other trees with generalized pollination system in karst forest landscape.