Plant-pollinator networks in the tropics

Camila Souza and colleagues recently had their paper on plant‐pollinator networks published in Journal of Ecology. Read more about the paper in the blog post below.

Many plants depend on pollinators for reproduction, especially in the tropics. The interaction between plants and pollinators in a community form complex networks which may change in structure across spatial and temporal gradients.

Despite a clear appreciation of the temporally-dynamic nature of plant phenology and assemblage of pollinators, their interaction networks are often treated as temporally static entities. In this sense, we lack understanding of temporal variation in the structure of interaction networks, especially in species rich tropical regions of the world.

In our paper, we evaluated the seasonal variation of four plant-pollinator networks from two seasonal ecosystems in Central Brazil, involving a total of 29,077 flower visits between 278 plants and 349 animal species.

Our study is the first to provide a quantitative description of seasonal changes in the metrics of plant-pollinator interaction networks in tropical areas. We characterized the seasonal dynamics of plant-pollinator interactions, using sequential standardized networks, testing the prediction that interactions would be more specialized when resources are more abundant (i.e., during the rainy season). To do so, we also quantified the temporal availability of floral resources, as well as their functional diversity.


Fig 1: Bombus morio visiting Pontederia cordata. The bumble bee was the most important native pollinator of the studied communities.

Contrary to our prediction, we found that dry season networks, characterized by lower floral resource abundance, showed higher levels of network-wide interaction partitioning (complementary specialization and modularity). Nestedness and functional diversity of floral resources, however, were not different between dry and rainy seasons. Moreover, we could show that targeted sampling of interactions during the peak flowering season (an approach sometimes used in the literature), led to overestimation of network-wide specialization.


Fig 2: Views of studied formations and year-round, rainy and dry season interactions networks between plants and pollinators (in yellow and green circles, respectively). The thickness of lines and size of circles represent the interaction frequency and the total number of interactions for each species, respectively.

Although unexpected, the higher specialization during the dry season illustrates the temporarily dynamic nature of plant-pollinator interaction networks from the tropics. Moreover, the choice of sampling period should be considered with caution when conducting studies in year-round active biodiverse regions as well as when making broad-scale temperate vs. tropical network comparisons, which should consider such bias. Finally, our plant-pollinator interaction data comes from some of the major sampling gaps in the plant-pollinator network literature, contributing to broaden our understanding of this system.

Camila Silveira Souza (Universidade Federal de Mato Grosso do Sul, Brazil) and Pietro Maruyama (Universidade Estadual de Campinas, Brazil)

Read the full paper: Temporal variation in plant‐pollinator networks from seasonal tropical environments: higher specialization when resources are scarce

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