Variation in the reproductive success of a narrow endemic plant: Effects of geographical distribution, abiotic conditions and pollinator community composition

摘要

Geographic variation in reproductive output determines plant distribution. In this study, we investigate the geographic structure and the factors affecting reproductive success throughout the life cycle of the near-threatened crucifer Erysimum popovii across its entire distribution range. We worked in 21 populations, in which we measured fruit set, seed set, seed weight, seed germination in the laboratory, germination time, seedling emergence in the field, seedling survival and fecundity. We also sampled the pollinator assemblages visiting E. popovii at each site, as well as some population characteristics (population size and density, flower density of E. popovii and other co-occurring species, and rainfall). Germination success in the laboratory was very high (range: 0.56-0.98), but seedling emergence in the field was low (0.005-0.32). Beefly visitation rate was positively related to seedling emergence, whereas visitation rate by ants, beetles and other minor pollinator groups was negatively related to fruit set and positively related to germination time. Populations in sites with high density of co-occurring flowers produced fewer fruits. Most variables related to reproductive output varied widely across populations, but this variation did not show a clear regional structure. The low seedling survival may constitute a bottleneck for the recruitment of this species. Overall, less than 0.2% of the ovules produced developed into reproductive individuals. Our results suggest a metapopulation structure for E. popovii.