Resource availability and competition shape pollinator trophic specialization in longleaf pine savannas.

Authors: MORENO-GARCIA, PABLO - University Of Florida; FREEMAN, JOHANNA - Florida Fish And Wildlife Conservation Commission; BALSER, BENJAMIN - University Of Florida; Campbell, Joshua; LI, DAIJIANG - Louisiana State University

Submitted to: Basic and Applied Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/13/2025
Publication Date: 1/14/2025
Citation: Moreno-Garcia, P., Freeman, J.E., Balser, B., Campbell, J.W., Li, D. 2025. Resource availability and competition shape pollinator trophic specialization in longleaf pine savannas.. Basic and Applied Ecology. 83, 118-127. https://doi.org/10.1016/j.baae.2025.01.004.
DOI: https://doi.org/10.1016/j.baae.2025.01.004

Interpretive Summary: Food resources that organisms specialize on is called 'trophic specialization'. Trophic specialization is important for understanding how different species survive and coexist within an ecosystem. Resource availability and species competition on trophic specialization have yet to be tested in plant-pollinator networks. We evaluated how resource availability and intraguild competition on three aspects of trophic specialization: (1) taxonomic specialization (pollinator selection of plant species), (2) phylogenetic specialization (pollinator selection of plant phylogenetic lineages), and (3) functional specialization (pollinator selection of plant functional traits) from pollinator and plant data collected from 24 pine savannas in north-central Florida. We found that the proportion of competing pollinator individuals is the main factor driving pollinator trophic specialization in xeric pine savannas, leading pollinators to interact with more plant species. These data highlights the plasticity of pollinator diets, but also the vulnerability of pollination services to pollinator extinctions.

Technical Abstract: Trophic specialization, the variability of food resources that a species utilizes, has important ecological implications for species survival and co-existence, as well as ecosystem functioning and resilience. Realized trophic specialization, or the food resources with which a species interact locally, is driven by resource availability (i.e., diversity and abundance), and the competitive interactions in which the target species participates (i.e., among species and individuals that perform similar roles in the ecosystem). However, the simultaneous effects of resource availability and species competition on trophic specialization have yet to be tested in plant-pollinator networks. Clarifying the roles of both processes in trophic specialization is essential to the understanding and conservation of species interactions and ecosystem functions and services. We disentangled the effects of resource availability (i.e., blooming plant diversity and abundance), and intraguild competition (i.e., proportion of competing pollinator individuals and overall pollinator species richness) on pollinator trophic specialization, using samples collected over an entire flowering season in 24 xeric pine savannas in north-central Florida. We evaluated the effects of resource availability and intraguild competition on three aspects of trophic specialization: taxonomic specialization (pollinator selection of plant species), phylogenetic specialization (pollinator selection of plant phylogenetic lineages), and functional specialization (pollinator selection of plant functional traits). We found that the proportion of competing pollinator individuals is the main factor driving pollinator trophic specialization in xeric pine savannas, leading pollinators to interact with more plant species, phylogenetic lineages, and functional traits in more competitive environments. The effect of competition highlights the plasticity of pollinator diets, but also the vulnerability of pollination services to pollinator extinctions.