Previous studies have examined separately how pollinator generalization and abundance influence plant reproductivesuccess, but none so far has evaluated simultaneously the relative importance of these pollinator attributes. Here weevaluated the extent to which pollinator generalization and abundance influence plant reproductive success per visit and atthe population level on a generalist plant,Opuntia sulphurea(Cactaceae). We used field experiments and path analysis toevaluate whether the per-visit effect is determined by the pollinator’s degree of generalization, and whether the populationlevel effect (pollinator impact) is determined by the pollinator’s degree of generalization and abundance. Based on themodels we tested, we concluded that the per-visit effect of a pollinator on plant reproduction was not determined by thepollinators’ degree of generalization, while the population-level impact of a pollinator on plant reproduction was mainlydetermined by the pollinators’ degree of generalization. Thus, generalist pollinators have the greatest species impact onpollination and reproductive success ofO. sulphurea.According to our analysis this greatest impact of generalist pollinatorsmay be partly explained by pollinator abundance. However, as abundance does not suffice as an explanation of pollinatorimpact, we suggest that vagility, need for resource consumption, and energetic efficiency of generalist pollinators may alsocontribute to determine a pollinator’s impact on plant reproduction.
