The role of seasonality and disturbance in bee-plant interactions in semi-arid communities of the southern Chihuahuan desert

The maintenance of interactions between plants and their floral visitors depends on factors such as resource variability, seasonality, and population dynamics. Changes in water availability along with different types and levels of anthropogenic disturbance may influence how plants and pollinators interact, especially in arid environments. In a semi-arid area of the southernmost Chihuahuan Desert (Mexico), we surveyed bee-plant interactions in the dry and rainy season at sites that differed in disturbance type. We used a mutualistic network approach to analyse our data. We collected 946 bee individuals belonging to 32 bee species, almost a third of the total richness previously reported for Queretaro state. We detected a strong impact of seasonality on the structure of ecological interactions, with more complex and robust interactions among bee and plant species in the rainy season. We did not find statistical support for a relationship among disturbance, nestedness, or niche overlap. We did find disturbance negatively affected plant robustness to secondary extinctions. Four plants: Echinocactus platyacanthus, Opuntia stenopetala, Senna wislizeni var. painteri and Cylindropuntia imbricata comprised the core species that were primarily responsible for the resilience of the bee communities. The following bees conformed the generalist core of species: Diadasia rinconis, Lasioglossum (Dialictus) sp. 1, Apis mellifera, and Augochlorella pomoniella. Overall, network nestedness and robustness differed significantly between seasons but not among sites with different levels of disturbance.