The diversity of mutualistic interactions in the Neotropics exceeds that of all other tropical regions, and is posited to result from a unique assemblage of plant species that produce the highest spatio-temporal predictability of food resources. A rare component of the Neotropical flora that contributes largely to the spatio-temporal predictability of food resources is found in understory shrub or treelet species with a continuous reproductive phenology (i.e. produce fruit and flowers daily during all months of the year). Plant-animal interaction science suggests that plant species with a longer duration of reproductive phenology will accumulate more mutualistic partners over time and therefore play a more central role in the network. Here we focus on plant-pollinator interactions within the lowland understory shrub community to ask: (a) Do shrub species with the continuous flowering phenology share the same role in networks and (b) Does network structure or shrub species role in the network change between seasons or interannually.
In June-July and December (2017-2018), 30-minute observation periods were conducted on native and naturally occurring flowering shrubs of the southern Pacific lowlands in Costa Rica. Plant-pollinator interactions and plant species role in the network were quantified using bipartite network analysis, Mueller’s index, and modularity analysis.
Results/Conclusions
Bipartite network analysis reveals shrubs with a continuous flowering phenology are connected within the network, but the degree of connectivity among the shrubs displaying this phenology is not evenly distributed, implying that other traits may be influencing hub selection within the network. Modularity analyses indicate focal shrubs share similar roles as peripherals (z-score<2.5, c-score<0.62), all except Hamelia patens which had high between module connectivity (z-score<2.5, c-score ≥ 0.62) therefore assigned a connector role. These results differ from theoretical studies relating flowering duration to network connectivity. Floral abundance and plant species have a significant influence on pollinator abundance and richness (p<0.001). Pollinator community composition and interaction composition varied between years, but the core set of interactions remained consistent. Not all plant species with the continuous flowering phenology may accumulate more partners over time as observed with more intermediate flowering phenologies, owing to the low abundance of flowers produced daily or the higher degree of interaction specialization.