Nectar robbing does not affect female reproductive success of an endangered Antirrhinum species, Plantaginaceae

Background: Nectar robbers in many plant species affect female reproductive success, usually decreasing the amount of seed produced by plants, which can affect populations persistence. Aims: To evaluate the impact of nectar robbers on the viability of the populations, we investigated the effects of nectar robbing on the female reproductive success of a threatened snapdragon species in four populations over 2 years. Methods: We observed insect visitors and their behaviour and quantified the percentage of robbed and non-robbed flowers and the production of fruits and seeds. Results: The results showed the degree of variation in nectar robbing among the populations and between years within the populations. Nectar robbers were detected in only two populations, and all were Bombus terrestris. Differences in flower size among populations were not related to the nectar robbing behaviour of B. terrestris. A comparison of the percentage of fructification and seed production between flowers that were and were not robbed showed no evidence of a negative effect of nectar robbing. Conclusions: Our study reports for the first time on nectar robbing in Antirrhinum species and concludes that this does not affect the female reproductive success of individuals or the viability of A. valentinum populations.