Plant-pollinator networks across scales

Background/Question/Methods

Species interaction networks depict complex webs of interactions among species. While these networks are often represented and analyzed as observations aggregated over time and space, examining the temporal and spatial dimensions of these networks can increase our understanding of the ecological and evolutionary processes that shape their structure and their response to human-caused environmental change. In recent years, there has been increased interest in the temporal and spatial aspects of species interaction networks. Patterns emerging from such studies include low variation in many network structural properties while at the same time high variation in interactions over time and space. Many knowledge gaps remain in our understanding of the spatiotemporal dynamics of networks, including understanding: the mechanisms driving temporal and spatial interaction variation, how interactions vary across scales, and how climate change and other anthropogenic impacts affect networks. To address these gaps, my colleagues and I have studied plant-pollinator interactions in the Colorado Rocky Mountains. In our work, we seek to understand how and why the structure and composition plant-pollinator networks change over temporal scales ranging from within a year to across a century and spatial scales ranging from within a meadow to across a 2500m elevation gradient.

Results/Conclusions

Within a subalpine meadow at the Mountain Research Station, we found that interactions between generalists tended to persist more in time and space such that interactions near the network core were more frequently recorded across seven years, within seasons, and among plots. We posit that species’ tolerance of environmental variation across time and space plays a key role in generalization by regulating spatiotemporal overlap with interaction partners. Our results imply a role of spatiotemporal environmental variation in organizing species interactions, marrying niche concepts that emphasize species environmental constraints and their community role. At a larger scale, we are evaluating the long-term change in a diverse plant-pollinator network by re-sampling data from a century-old classic study on community-wide plant-pollinator interactions conducted by Clements and Long (1923) on Pikes Peak. Our data show surprisingly high persistence of species, interactions, and network structural properties. These results highlight the critical role that regional habitat conservation plays in maintaining biodiversity and the integrity of interaction networks in the face of climate change.