Grooming intensity and stigma position alter the mating network among plants

Grooming by pollen vectors and the positioning of floral reproductive organs jointly influence pollen transfer by shaping where pollen grains are deposited on, redistributed on, and removed from the vector’s body, thereby affecting plant mating patterns. Linking these processes to reproductive outcomes requires tracking the fate of individual pollen grains, which remains challenging. We used a spatially explicit agent-based model to simulate sequential floral visits by pollen vectors with varying grooming intensities to flowers differing in anther and stigma positions. From these simulations, we generated quantitative mating matrices and analyzed mating patterns at both the population and individual levels. Grooming reduced the proportion of realized mating interactions relative to all possible plant pairings (“connectance”), while increasing partner exclusivity (“specialization”) and clustering (“modularity”). These changes in mating network structure concentrated pollen exchange within smaller plant groups, reducing mating partner diversity and substantially weakening the influence of floral morphological variation. Without grooming, by contrast, variation in stigma position increased mating diversity, and visit order intensified first-male and last-female advantages. Overall, grooming seems to constrain the diversity of effective mating interactions and diminishes the functional impact of stigma position, promoting more uniform and selective mating patterns. In bee-pollinated plants, this may favor stabilizing selection on stigma positions, whereas in low-grooming systems, greater variation in stigma positions may be tolerated or even advantageous.