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

Abstract

Pollinators may influence plant community assembly through biotic filtering and/or plant–plant competition and facilitation. The relative importance of each process, however, vary according to the scale and how strongly plants share their pollinators, and possibly in relation to the pollinator groups considered. We here investigated the assembly of three Atlantic forest hummingbird‐pollinated plant communities across space (among all species in the communities) and time, i.e. yearly flowering phenology (between pairs of co‐flowering species), based on the pairwise distances of multiple floral traits (corolla length, anther and stigma height, colour and nectar). Because tropical hummingbird‐pollinated plants are often subdivided in two pollination niches (hermits versus non‐hermits), we also analyzed these groups separately. We found that trait structure across space was clustered for some floral traits, suggesting biotic filtering and facilitation. All floral traits had weak phylogenetic signal, indicating that closely related species were not more similar than distantly related species. Moreover, floral traits were randomly structured along the phenology when analyzing all plants together. On the other hand, we found similar corolla length but divergent anther height in co‐flowering pairs within the same pollination niche. Thus, plants may benefit from flowering together and avoid competition through fine adjustments in reproductive traits. The results also suggest that clear signals of competition and facilitation among plants are only apparent when species strongly share their pollinators and depending on the traits that are considered. Our study illustrates a complex interplay of biotic filtering, facilitation and competition as processes structuring guilds of plants sharing the same functional group of pollinators.

Pollination outcomes reveal negative density‐dependence coupled with interspecific facilitation among plants

“…Hummingbird-pollinated plants experienced facilitation and competition in similar proportions. Previous studies suggested an interplay of facilitation and competition on hummingbird-pollinated plant communities Bergamo et al 2018), and our results confirm that both interaction signs are similarly important for these plants. CONCLUSION Pollination success was greatest when a plant was rare on a landscape scale but occurred in locally dense patches of conspecific or heterospecific flowers.…”

How does urbanization affect the reproductive characteristics and ecological affinities of street plant communities?

“…Desaegher et al (2018) showed that floral visitors of insect families that had a preference for nontubular corollas (generally insects with small mouthparts and considered as specialists) were rare in urbanized areas of the Île-de-France region (see also Geslin, Gauzens, Thébault, & Dajoz, 2013). In different contexts, two recent community-level studies (Bergamo, Wolowski, Maruyama, Vizentin-Bugoni, & Sazima, 2018;Fantinato, Del Vecchio, Giovanetti, Acosta, & Buffa, 2018) suggested complex interplay of facilitation and competition processes among flowering plants through pollination by insects. In different contexts, two recent community-level studies (Bergamo, Wolowski, Maruyama, Vizentin-Bugoni, & Sazima, 2018;Fantinato, Del Vecchio, Giovanetti, Acosta, & Buffa, 2018) suggested complex interplay of facilitation and competition processes among flowering plants through pollination by insects.…”

“…In different contexts, two recent community-level studies (Bergamo, Wolowski, Maruyama, Vizentin-Bugoni, & Sazima, 2018;Fantinato, Del Vecchio, Giovanetti, Acosta, & Buffa, 2018) suggested complex interplay of facilitation and competition processes among flowering plants through pollination by insects. This differentiation may allow different pollen placement on pollinator bodies, which can reduce competition among plant species and increase effective pollination (Bergamo et al, 2018;Fantinato et al, 2018). These studies also showed that coflowering, pollinator-sharing species tended to differ in another position in the corollas.…”

“…This is consistent with the results of Deguines, Julliard, Flores, and Fontaine (2016), who showed that urbanization was associated with a shift in community composition of flower visitors toward generalist insects in France. In different contexts, two recent community-level studies (Bergamo, Wolowski, Maruyama, Vizentin-Bugoni, & Sazima, 2018;Fantinato, Del Vecchio, Giovanetti, Acosta, & Buffa, 2018) suggested complex interplay of facilitation and competition processes among flowering plants through pollination by insects. Both studies showed that, in a given area, plant species sharing the same pollinator guild tended to flower together (phenological synchronization), which can be interpreted as a pollinator-mediated facilitation by increasing pollinator attraction in dense flowering patches (Sargent & Ackerly, 2008).…”

“…These studies also showed that coflowering, pollinator-sharing species tended to differ in another position in the corollas. This differentiation may allow different pollen placement on pollinator bodies, which can reduce competition among plant species and increase effective pollination (Bergamo et al, 2018;Fantinato et al, 2018). The different mechanisms by which competition for pollinators can reduce plant fitness include low frequency of pollinator visits and heterospecific pollen deposition on stigmas, and were described in detail by Waser (1978).…”