Exploring extinction simulations in Lepidoptera-plant pollination and herbivory networks

Link To Share This Poster: https://cdmcd.co/v9DZRY

Rhea Amatya and Christopher T. Cosma, Department of Evolution, Ecology, and Organismal Biology, University of California Riverside, Riverside, CA

Background/Question/Methods
Ecological networks are a powerful tool for analyzing communities and informing conservation. The structure of these networks influences community robustness to species extinctions. Network studies have predominantly focused on a single interaction type (e.g., plant-pollinator). However, combining multiple interaction types may alter predictions about the effects of climate change-driven species losses.
Mutualistic (pollination) and antagonistic (herbivory) networks can be linked through shared plant species. Lepidoptera provide a unique study system to investigate these linked networks because butterflies and moths are important herbivores and pollinators in their larval and adult stages, respectively. Further, Lepidoptera are more sensitive to climate change than other insects, and their populations are declining. Here, we adapt data from a naturalists’ guide detailing Lepidoptera-plant pollination and herbivory interactions for native California plants to ask: 1) How does the structure of pollination and herbivory networks differ? and 2) How does network structure influence community response to simulated species extinctions?
We recorded each pairwise interaction from the guide and converted the data into interaction matrices. Using the R package ‘bipartite’, we analyzed and compared the structure of each network. We also simulated species extinctions and measured the area under the resulting extinction curves as a measure of robustness.
Results/Conclusions
Preliminary results suggest that pollination networks are less modular than herbivory networks (“modularity” of 0.377 and 0.785, respectively), and that pollination networks are more nested than herbivory networks (“NODF” of 6.697 and 2.020, respectively). Pollination networks are also more robust to both plant and insect species extinctions, which supports previous findings that higher nestedness and lower modularity increases network robustness. This also suggests that if a plant species is lost, its herbivore partners may not be able to interact with other plant species in the community, and emphasizes the need to protect host plant diversity. Moving forward, we will perform targeted species extinction simulations based on information about current responses and vulnerabilities of plant and Lepidoptera species to global change. We will also identify “keystone” plant and insect species by analyzing species roles in modules. Finally, we will incorporate phylogenetic information and analyze these networks in a multilayer modeling framework in order to investigate how multiple interaction types influence community response to perturbations. This research will help guide conservation efforts aimed at protecting native Lepidoptera and plant species in California, a biodiversity hotspot threatened by multiple anthropogenic drivers.