Invasive woody plants as foci of tick-borne pathogens: eastern redcedar in the southern Great Plains

Panarchy theory for convergence

Coping with surprise and uncertainty resulting from the emergence of undesired and unexpected novelty or the sudden reorganization of systems at multiple spatiotemporal scales requires both a scientific process that can incorporate diverse expertise and viewpoints, and a scientific framework that can account for the structure and dynamics of interacting social-ecological systems (SES) and the inherent uncertainty of what might emerge in the future. We argue that combining a convergence scientific process with a panarchy framework provides a pathway for improving our understanding of, and response to, emergence. Emergent phenomena are often unexpected (e.g., pandemics, regime shifts) and can be highly disruptive, so can pose a significant challenge to the development of sustainable and resilient SES. Convergence science is a new approach promoted by the U.S. National Science Foundation for tackling complex problems confronting humanity through the integration of multiple perspectives, expertise, methods, tools, and analytical approaches. Panarchy theory is a framework useful for studying emergence, because it characterizes complex systems of people and nature as dynamically organized and structured within and across scales of space and time. It accounts for the fundamental tenets of complex systems and explicitly grapples with emergence, including the emergence of novelty, and the emergent property of social-ecological resilience. We provide an overview of panarchy, convergence science, and emergence. We discuss the significant data and methodological challenges of using panarchy in a convergence approach to address emergent phenomena, as well as state-of-the-art methods for overcoming them. We present two examples that would benefit from such an approach: climate change and its impacts on social-ecological systems, and the relationships between infectious disease and social-ecological systems.

Effects of woody plant encroachment by eastern redcedar on mosquito communities in Oklahoma

Woody plant encroachment into grasslands is occurring worldwide, affecting ecosystems in ways that likely influence mosquito-borne disease transmission. In the U.S. Great Plains, encroachment by eastern redcedar (Juniperus virginiana) (ERC) may be expanding conducive habitat for mosquitoes and their hosts, but few studies have evaluated associations between ERC encroachment and West Nile virus (WNV). To test the hypotheses that mosquito abundance and WNV-infected mosquitoes increase with increasing ERC cover, we collected mosquitoes in 32 sites in Oklahoma reflecting various ERC encroachment stages. We found support for our first hypothesis, as mean abundance of Aedes albopictus increased significantly with ERC cover. However, Psorophora columbiae and Anopheles quadrimaculatus abundance decreased with increasing ERC. There was no significant association with ERC for other mosquito species. We could not test our second hypothesis due to low WNV prevalence, but the only detected WNV-infected pool of mosquitoes (Cx. tarsalis) was collected in ERC. Our results suggest ERC encroachment increases abundance of at least one medically important mosquito species, but further research is needed to clarify how encroachment affects ecology of the entire WNV disease system through changes to vector and host communities, vector-host interactions, and thus disease transmission and prevalence. Understanding relationships between woody plant encroachment and the nidus of infection for mosquito-borne diseases will be crucial for targeting public health efforts, including land management activities that limit and/or eradicate woody plant encroachment, particularly in areas with high levels of disease risk.

Seasonality of Ticks and Prevalence of Rickettsiae Species in Dermacentor variabilis and Amblyomma maculatum Across Oklahoma Pastures

Tick-borne diseases are an increasing concern for people and companion animals in the United States, but there is a need for continued vigilance regarding livestock in pasture systems. The south-central United States has some of the highest incidences of tick-borne diseases, and there is a need to re-examine the ecology of tick vectors in relation to pasture systems and livestock. The objective of this study was to establish a baseline of seasonal activity for tick species in diverse regional Oklahoma pastures and screen for important pathogens in Dermacentor variabilis (Say) and Amblyomma maculatum Koch group that may impact livestock and human health. Between 2015 and 2017, transects in five pastures across Oklahoma were visited each month. DNA extracted from adult D. variabilis and A. maculatum group was tested for the presence of bacterial pathogens. We found that tick communities in pastures across Oklahoma differ by season, abundance, and bacterial presence and prevalence. The peak abundance of Amblyomma americanum (L.) adults and nymphs occurred a month earlier over the 2 yr of the study compared with historical studies in the same regions. Additionally, we observed notable differences in peak activity between A. americanum adults and nymphs collected in pastures in central Oklahoma (April) versus pastures in northern part of the state (May). We detected Rickettsia parkeri, R. bellii, and Anaplasma sp. DNA in D. variabilis from pastures across the state. These results potentially have important ramifications for human and livestock risk of encountering infected ticks in pastures across the southern Great Plains.

Invasive Plants as Foci of Mosquito-Borne Pathogens: Red Cedar in the Southern Great Plains of the USA

West Nile virus (WNV) is the most significant mosquito-borne disease affecting humans in the United States. Eastern redcedar (ERC) is a native encroaching plant in the southern Great Plains that greatly alters abiotic conditions and bird and mosquito populations. This study tested the hypotheses that mosquito communities and their likelihood of WNV infection differ between ERC and other habitats in the southern Great Plains of the United States. We found support for our first hypothesis, with significantly more Culex tarsalis and Culex erraticus in ERC than deciduous and grass habitats. Mosquito communities in Central Oklahoma were more diverse (21 species) than western Oklahoma (11 species) but this difference was not associated with vegetation. Our second hypothesis was also supported, with significantly more WNV-infected Culex from ERC in both regions, as was our third hypothesis, with significantly more Culex tarsalis and Culex pipiens collected in ERC than other habitats in urban areas. The connection of mosquito-borne disease with invasive plants suggests that land management initiatives can affect human health and should be considered in light of public health impact. Evidence from other vector-borne disease suggests invasive plants, both in the Great Plains and globally, may facilitate the transmission of vector-borne pathogens.