Reproductive success, fruit removal and local distribution patterns in the early-flowering shrub Daphne mezereum

In insect-pollinated, bird-dispersed plants, both investment in reproduction and reproductive success involve interactions between plants and their pollinators and dispersers. The outcome of these plant-animal interactions may be affected by the number of flowers and fruits, as well as by the plants' local environment and by spatial associations among plants. In this study we mapped the spatial distribution of individuals in a population of the early flowering, fleshy-fruited shrub Daphne mezereum, in a forest in boreo-nemoral Sweden. For all mapped individuals we collected data on numbers of flowers and fruits and fruit removal, for three consecutive years. We analysed spatial associations among individuals, and the effects on reproductive performance and fruit removal of plant height, numbers of flowers and fruits, distance to forest edge, and neighbouring flower and fruit density. Our results show that the density of D. mezereum increases with increasing proximity to forest edge. The number of flowers produced, as well as fruit set and fruit removal, show the same positive relationship with increasing proximity to forest edges. We further show that individuals are aggregated up to distances of about 10 m. The flower production of neighbouring conspecific individuals within 10 m is negatively related to fruit set whereas the fruit production of neighbours is positively related to fruit removal. Our main conclusion is that the spatial distribution of D. mezereum affects reproductive success and fruit removal, which in turn has the potential to feed back to the spatial distribution pattern. Combining studies of reproduction with spatial analyses is important to advance our understanding of the dynamics of plant populations.

Automated summary

In this study, the spatial distribution of Daphne mezereum in a forest in Sweden was mapped, showing a positive correlation between the density of individuals and proximity to the forest edge. The number of flowers produced, fruit set, and fruit removal also showed a positive relationship with proximity to forest edges. The study also found that individuals of D. mezereum were aggregated within approximately 10 meters. The flower production of neighboring individuals within 10 meters was negatively related to fruit set, while the fruit production of neighbors was positively related to fruit removal. The spatial distribution of D. mezereum affects reproductive success and fruit removal, which can, in turn, influence the spatial distribution pattern.