Biodiversity and connectance enhance the resilience of plant-pollinator networks under global environmental change

Heng Huang, Chengyi Tu and Paolo D'Odorico, Department of Environmental Science, Policy, and Management, University of California at Berkeley, Berkeley, CA

Background/Question/Methods
The global pollinator decline has received considerable attention among ecologists. Understanding the dynamic behavior and resilience of plant-pollinator communities under global change is crucial to the maintenance of biodiversity and ecosystem stability. Observational studies have suggested that disturbances such as habitat loss have significant cascading effects on plant-pollinator dynamics, it remains unclear, however, how plant-pollinator systems quantitatively respond to increasing disturbances through inbreeding-reward-pollinator feedbacks. It has been well recognized that plants may reduce the production of flowers and the associated floral rewards under environmental stress which can discourage pollinator visits and increase selfing, and in turn decrease vegetation growth due to inbreeding suppression. Nevertheless, a quantitative analysis of this positive internal feedback and its consequences for the dynamics of plant-pollinator communities is missing. In addition, the role of ecosystem complexity such as biodiversity and connectance in the stability and resilience of plant-pollinator systems remains poorly understood. In this study, we develop a multi-species process-based model coupled with 143 empirical networks across the globe to explore plant-pollinator dynamics under increasing environmental change.
Results/Conclusions
We found that increasing disturbance intensity can induce community-wide abrupt extinctions in plant-pollinator systems through positive feedbacks. In particular, the responses of plant-pollinator systems are hysteretic and depend on the initial conditions of species abundance. Thus, collapses of plant-pollinator systems could be highly irreversible, which results in the direct loss of associated ecosystem functioning and services. We also found that network connectance and biodiversity promote the stability of plant-pollinator systems, in contrast to previous studies. Furthermore, our work suggests a weak positive effect of network nestedness on the dynamic behavior of plant-pollinator systems. Thus, relative to nestedness, connectance and biodiversity appear to play a more crucial role in determining the resilience and stability of plant-pollinator systems. Our findings highlight the critical role of positive plant-reward-pollinator feedbacks in driving critical transitions in plant-pollinator communities - especially those with low degree of biodiversity and network connectance - under global change.