The potential indirect effects among plants via shared hummingbird pollinators are structured by phenotypic similarity

Abstract

Plant species within communities may overlap in pollinators' use and influence visitation patterns of shared pollinators, potentially engaging in indirect interactions (e.g., facilitation or competition). While several studies have explored the mechanisms regulating insect-pollination networks, there is a lack of studies on bird-pollination systems, particularly in species-rich tropical areas. Here, we evaluated if phenotypic similarity, resource availability (floral abundance), evolutionary relatedness and flowering phenology affect the potential for indirect effects via shared pollinators in hummingbird-pollinated plant species within four communities in the Brazilian Atlantic forest. Among the evaluated factors, phenotypic similarity (corolla length and anther height) was the most important variable, while resource availability (floral abundance) had a secondary importance. On the other hand, evolutionary relatedness and flowering phenology were less important, which altogether highlights the relevance of convergent evolution and that the contribution of a plant to the diet of the pollinators of another plant is independent of the level of temporal overlap in flowering in this tropical system. Interestingly, our findings contrast with results from multiple insect-pollinated plant communities, mostly from temperate regions, in which floral abundance was the most important driver, followed by evolutionary relatedness and phenotypic similarity. We propose that these contrasting results are due to high level of specialization inherent to tropical hummingbird-pollination systems. Moreover, our results demonstrated that factors defining linkage rules of plant-hummingbird networks also determinate plant-plant potential indirect effects. Future studies are needed to test if these findings can be generalized to other highly specialized systems. Overall, our results have important implications for the understanding of ecological processes due resource sharing in mutualistic systems.

Functional diversity mediates macroecological variation in plant–hummingbird interaction networks

“…A closer association between network specialization and consumer FD, but not plant FD, may also result from phenological differences between plants and animals. Although many hummingbird species are constantly present in the community, the turnover of flowering plant species is usually high, suggesting that morphologically specialized plant species may be replaced by functionally similar species temporarily (Bergamo et al, ; Weinstein & Graham, ). Thus, plant assemblages may have greater species redundancy, and the processes driving niche partitioning may differ between plants and animals.…”

Evolutionary history as a driver of ecological networks: a case study of plant–hummingbird interactions

“…Data on phenology consisted of the monthly presence or absence of individuals (hummingbirds) and open flowers (plants) of each species during 24 months of data collection. We considered the corolla length as the main morphological constraint to hummingbirds' access to nectar (Bergamo et al 2017). Therefore, we used measurements of the corolla tube length of plants and of the bill reach of hummingbirds.…”

Trait patterns across space and time suggest an interplay of facilitation and competition acting on Neotropical hummingbird‐pollinated plant communities

“…The role of pollinators on the structuring of plant communities may become evident by considering distinct floral traits (Gegear and Laverty 2001). For instance, resource accessibility (corolla length) and availability (nectar sugar content) can influence the composition of pollinator assemblage associated to a flower and thus the degree of pollinator-sharing between plants and their potential indirect effects (Carvalheiro et al 2014, Nottebrock et al 2016, Bergamo et al 2017. Meanwhile, floral signals and rewards influence pollinator attraction and foraging strategy among species.…”

“…Further specialization into distinct pollination niches can be found within the hummingbird-pollinated plant communities, regulated by corolla-bill length matching and other morphological and behavioral traits (Murray et al 1987, Maruyama et al 2014, Maglianesi et al 2015. Moreover, phylogeny-based analyses often show a low influence of evolutionary relatedness influencing plant-hummingbird interactions and, consequently the associated floral traits (Bergamo et al 2017, Wolowski et al 2017. Therefore, hummingbird-pollination could act as a filter on the community assembly, leading to communities composed by functionally similar plant species from distinct lineages (Wolowski et al 2017).…”

“…For these communities, we have extensive knowledge on species composition, life history (i.e. flowering phenology, floral traits and pollen limitation), and pollination (Sazima et al 1995, Buzato et al 2000, Wolowski et al 2013, Maruyama et al 2015, Vizentin-Bugoni et al 2016, Bergamo et al 2017. We evaluated trait patterns among all plant species in the community and between co-flowering species pairs.…”