Variation in pollinator assemblage along a Mediterranean urbanization gradient does not affect the reproductive output of the wild radish

Land use affects plant–pollinator interactions, altering pollinator community composition and plant reproductive success. Rural–urban gradients offer useful models for assessing the effects of anthropogenic activity on these interactions. We surveyed pollinators and two plant reproductive traits (i.e., fruit and seed set) of Raphanus raphanistrum in a total of 18 populations located in three land cover classes (seminatural, agricultural and urban) defining a Mediterranean rural-urban gradient. We first built plant-pollinator networks and calculated the total number of pollinator visits, the relative contribution of different wild pollinator categories and that of wild vs. managed pollinators. Then, we estimated the contribution of pollinator functional traits in the three land cover classes. Lastly, we tested for an effect of pollinator assemblage and pollinator abundance on plant reproductive traits. Pollinator assemblage varied along the gradient and pollinator diversity was lower in urban areas. Honeybees contributed equally in agricultural areas whilst wild pollinators were predominant in urban and seminatural areas. In seminatural areas Syrphidae were more abundant. Pollinator functional traits varied along the gradient. The total number of pollinator visits was comparable along the gradient, explaining the similar levels of fruit and seed set. Our findings suggest that urbanization can alter pollinator assemblage by reducing pollinator diversity, but generalist plants might maintain stable reproductive success by leveraging a broad range of pollinator classes. This resilience underscores the potential for generalist species to persist in changing environments and highlights the need to monitor the functional integrity of pollination networks in the face of habitat transformation.