Species’ floral traits and flowering times are known to be the major drivers of pollinator-mediated plant-plant interactions in diverse co-flowering communities. However, their simultaneous role in mediating plant community assembly and plant-pollinator interactions is still poorly understood. Since not all species flower at the same time, inference of facilitative and competitive interactions based on floral trait distribution patterns should account for fine phenological structure (intensity of flowering overlap) within co-flowering communities. Such an approach may also help reveal the simultaneous action of competitive and facilitative interactions in structuring co-flowering communities.

Here we used modularity within a co-flowering network context, as a novel approach to detect convergent and/or over-dispersed patterns in floral trait distribution and pollinator sharing. Specifically, we evaluate differences in floral trait and pollinator distribution patterns within (high temporal flowering overlap) and among co-flowering modules (low temporal flowering overlap). We further evaluate the consistency of observed floral trait and pollinator sharing distribution patterns across space (three geographic regions) and time (dry and rainy seasons).

We found that floral trait similarity was significantly higher in plant species within co-flowering modules than in species among them. This suggests pollinator facilitation may lead to floral trait convergence, but only within co-flowering modules. However, our results also revealed seasonal and spatial shifts in the underlying interactions (facilitation or competition) driving co-flowering assembly, suggesting that the prevalent dominant interactions are not static.

Synthesis: Overall, we provide strong evidence showing that the use of flowering time and floral trait distribution alone may be insufficient to fully uncover the role of pollinator-mediated interactions in community assembly. Integrating this information along with patterns of pollinator sharing will greatly help reveal the simultaneous action of facilitative and competitive pollinator-mediated interactions in co-flowering communities. The spatial and temporal variation in flowering and trait distribution patterns observed further emphasize the importance of adopting a more dynamic view of community assembly processes.

Pollinator community

To record the identity of pollinators visiting each plant species we conducted pollinator observations during each sampling day within the same plots where flowering species composition and flower density were recorded (see above). Each plot was observed for three 5-minute observation periods per day for a total of 15 min plot/day (total of 150 min per site/day).

Floral traits

For each flowering plant species we measure flower length, full corolla diameter and corolla tube opening 1-5 flowers per plant (averaged for analyses) in at least ten plants per species using a precision caliper (± 0.1 mm). We also measured floral reflectance spectra (300-700 nm) from the dominant corolla color in 1-3 flowers per species with a field spectrophotometer (StellarNet INC).

To evaluate differences in pollinator sharing within and among co-flowering modules we estimated the degree of pollinator sharing between plant species pairs using Gower's pairwise distances based on the number of visits by each functional group to each plant species. Pollinator sharing (1 – average dissimilarity) thus represents the degree of similarity in the pollinator community between two plant species. To estimate the degree of plant species floral trait similarity we first build a trait matrix containing the value of each functional trait. Then, we calculated trait distances between pairs of species and estimated species’ average floral trait similarity (across all traits) to the rest of the community using Gower's pairwise distance (1 – average dissimilarity).  

This database contains:

• Plant species codes: the scientific name (identity) and codes of each plant species recorded in the coastal dunes of the Yucatan Peninsula, Mexico.
• Pollinator sharing: data on pollinator sharing (i.e. similarity in pollinator use) of plant species pairs, type of interaction (Within-module or Among-module), region (West, Central and East) and the region in which the data were collected. 
• Floral trait similarity: floral trait similarity of plant species pairs, type of interaction (Within-module or Among-module),  region (West, Central and East) and the region in which the data were collected.