Unravelling the mechanisms determining facilitation and competition in plant-plant interactions mediated by pollinators

• Grant number: 25/06026-9
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: August 01, 2025
• End date: January 31, 2029
• Field of knowledge: Biological Sciences - Ecology
• Principal Investigator: Pedro Joaquim Bergamo
• Grantee: Lucas Benício de Castro
• Host Institution: Instituto de Biociências (IB). Universidade Estadual Paulista (UNESP). Campus de Rio Claro. Rio Claro , SP, Brazil

Abstract

Interactions between plants through shared pollinators can have both positive (facilitation) and negative (competition) effects on the reproductive success of co-flowering species. However, it remains unclear which mechanisms determine the reproductive success of plants that share pollinators. Floral trait similarity is a mechanism that can promote either competition or facilitation. In this context, the tolerance of neighbouring species to the arrival of heterospecific pollen on their stigmas also plays a key role in shaping competition vs. facilitation dynamics. Moreover, the interaction between floral traits and flower density can lead to either attenuated or saturated effects of facilitation and competition. This project will use the high-altitude grassland vegetation as a study model. This ecosystem is characterised by a low frequency of pollinators, which means that both the generalist flora-pollinated by flies and small bees-and the specialist flora-pollinated by hummingbirds-are subject to strong indirect effects due to intense pollinator sharing.In these high-altitude grasslands, we will conduct field experiments to address the following questions:(i) How does the removal of an abundant facilitating species affect the reproductive success of neighbouring plants?(ii) Does the effect of floral trait similarity on plant-plant interactions mediated by pollinators depend on flower density? (iii) Is heterospecific pollen tolerance influenced by differences in stamen height among co-flowering hummingbird-pollinated species? Finally, we will conduct a meta-analysis to test flower density and floral trait similarity as moderators of the effect size of plant-plant interactions. These approaches will strengthen the connection between pollination and community structure, advancing our understanding of the role of pollination and pollinator sharing in plant communities.