Floral visitors and pollinator dependence are related to floral display size and plant height in native weeds of central Mexico

Pollinator dependency is a life history trait that affects the evolutionary trajectory of individual plant species and their pollinators. It has consequences for plant communities, particularly in the context of human-modified landscapes. We used Mesoamerican weed vegetation as a model to explore the influence of structural plant features on the relationship of plants with pollinators. This vegetation type has some characteristics that are different from the well-known communities of Mediterranean/European origin; the differences are mostly related to the stature of the most important crop, maize. We evaluated the effect of an inflorescence bagging experiment on seed set to assess pollinator dependence of the ten most important species, all native annual herbs, in two maize fields of the central Mexican highlands and observed floral visitors. The tallest herbs had the largest floral display and the most visitors. They were dependent on animal pollination for seed set, which is unusual for annual plants and more so for weeds. Medium-sized species in the interior of the field were facultatively pollinator-dependent, and small species fully dependent on autonomous self-pollination. Pollinator dependency was correlated with plant stature and floral display area, probably related to conspicuousness or ease of detection by animals. We conclude that plant species composition of this vegetation type is related to pollinator access.