Shared pollinators and sequential flowering phenologies in two sympatric cactus species

Background and aims - The reproductive characteristics of sympatric Cactaceae are important because they help to understand interfering or facilitating mechanisms that allow their coexistence. Globose Cactaceae show melittophily flowers that may be attractive to a shared set of pollinators, and if the flowering events are not overlapping, flower resources could be present for the pollinators through time. Ariocarpus kotschoubeyanus and Neolloydia conoidea are two sympatric cactus species in the southern Chihuahuan Desert. The objective of this study is to describe and compare some reproductive characteristics of these species. Material and methods - Individuals of Ariocarpus kotschoubeyanus and Neolloydia conoidea (n = 231 and 212, respectively) were marked and monitored during one year, recording for each species, the floral phenology, behaviour and morphology, flower visitors, breeding and mating systems (through pollination experiments). Key results - The flowering periods of these species do not overlap. The flowers of both species are melittophily, with the same shape, colour, and similar behaviour; both are obligate xenogamous plants. The mating system of Neolloydia conoidea is outcrossing but mixed in Ariocarpus kotschoubeyanus. They share 75% of pollinators (solitary and social bees). Conclusions - The temporal blooming separation of these species could be an important factor to facilitate coexistence within the xerophyte community since they share the same set of pollinators to achieve their reproductive success.