Biocomplexity

PIERC Research: Biocomplexity of introduced avian diseases in Hawaii: threats to biodiversity of native forest ecosystems

Biocomplexity arises from the dynamic biotic and abiotic interactions that span several levels of biological systems. These interactions typically lead to a variety of complex and frequently unexpected ecosystem behaviors. As the number and levels of interactions increase, complexity and uncertainty can also increase. Although significant advances have been made in understanding the epidemiology of infectious diseases in human populations, similar advances in the epizootiology of infectious diseases have not occurred for wildlife populations. The emergence of disease problems in wildlife has increasingly been recognized as a threat to biological diversity as well as human health.

Introduction of mosquito-borne avian malaria and pox virus to Hawaii provides an outstanding example of how invasive diseases can have a profound effect on natural populations. This disease system is dynamic and complex, involving both direct and indirect interactions among endemic and introduced avian hosts, mosquito vector, parasites (Poxvirus and Plasmodium), and environmental conditions that extend across multiple temporal and spatial scales. Van Riper et al. (1986) presented a simple but powerful model for predicting intensity of malaria transmission in montane Hawaiian rainforests by overlaying mosquito and host distributions over an elevational gradient. Malaria transmission appeared to be most intense in mid-elevation forests where highly susceptible native forest birds overlapped in distribution with the introduced vector of pox and malaria, Culex quinquefasciatus. However, more recent work has shown that this simple model is generally applicable in areas with steep altitudinal gradients, but fails to explain recent emergent phenomena such as persistence of some highly susceptible native species in low elevation habitats.

This research project was funded by the National Science Foundation from 2001-2005. The research used a modeling approach to merge laboratory and field studies across scales from the gene to the landscape, and involved the disciplines of genetics and evolution, disease ecology, vector biology, avian ecology, climate and weather, and spatial and metapopulation ecology. This research was an integrated effort involving scientists at PIERC, the University of Hawaii, the Smithsonian Institute, Princeton University, and the USGS National Wildlife Health Center. The overall objectives of the project were to understand how introduced avian malaria and pox virus are impacting the endangered Hawaiian forest bird community and determine how specific management actions might alter long-term trends in the decline and extinction of the endemic Hawaiian avifauna. Ultimately we anticipate applications to other disease systems of concern to both humans and wildlife.

• Biocomplexity of Introduced Avian Diseases in Hawai'i: Threats to Biodiversity of Native Forest Ecosystems (pdf) USGS Fact Sheet
• Feral Pigs, Introduced Mosquitoes, and the Decline of the Hawaiian Honeycreepers (pdf) USGS Fact Sheet
• Vector subproject
• Pathogens subproject
• Bird food ecology subproject
• Host demography subproject
• Host population persistence in the face of introduced vector-borne diseases (pdf)
  
  Visit the project website for more details: http://www.uhh.hawaii.edu/~biocomp/