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United States Department of Agriculture

Agricultural Research Service

Research Project: INTEGRATED BIOSYSTEMATICS AND TAXONOMY FOR PARASITES AMONG UNGULATES AND OTHER VERTEBRATES Title: Beyond Vicariance: Integrating Taxon Pulses, Ecological Fitting and Oscillation in Evolution and Historical Biogeography

Authors
item Hoberg, Eric
item Brooks, Daniel - UNIV OF TORONTO, CANADA

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: June 10, 2009
Publication Date: June 1, 2010
Citation: Hoberg, E.P., Brooks, D. 2010. Beyond Vicariance: Integrating Taxon Pulses, Ecological Fitting and Oscillation in Evolution and Historical Biogeography. In: Morand, S., Krasnov, B. editors. The Geography of Host-Parasite Interactions. Oxford, England: Oxford University Press. p. 7-20.

Interpretive Summary: Parasite-host associations are complex and substantial research over the past 50 years has contributed to explanations for the biological and physical processes that serve to structure faunas in space and time. Association by descent (coevolution) and geographic distributions linked to isolation have represented the primary explanations for evolution and biogeography, but this represents an incomplete picture of historical events and processes. A new general model for the evolution of parasite biotas is developed to explain biogeographical distributions, host colonization and the evolution of host range. Host switching and geographical dispersal of parasites are common phenomena, occurring on many temporal and spatial scales. Diversification involves both coevolution and colonization to explain complex host ¬ parasite associations. Across the expanse of earth history, the major radiations in parasite-host assemblages have been preceded by ecological disruption, ecological breakdown and host switching. Major episodes of environmental change appear to be the main drivers for both persistence and diversification of host-parasite systems, creating opportunities for host switching during periods of geographic expansion and allowing for cospeciation and coadaptation during periods of relative stasis and geographic isolation. The patterns and dynamics of contemporary host-parasite associations emerge from an evolutionary context in which geographic distributions play a key role. Practical implications in agriculture are apparent because historical host switching, or acquisition of novel and naïve hosts is analogous to processes linked to contemporary emergence of infectious agents or disease (EID). An equivalence or uniformity for processes in space and time, suggests that history (e.g., coevolution and biogeography) can be applied to a broadened understanding of the EID crisis providing a basis for prediction and a shift from a reactive to proactive approach. Lessons learned from the study of historical diversity and diversification serve as analogues for defining determinants in shallow time or in contemporary systems, an issue particularly significant in effectively predicting and responding to emergent or invasive parasites and pathogens. Much of what we observe today is a legacy of a deeper evolutionary history, and neglecting that history reduces management policies to often inadequate crisis response.

Technical Abstract: Host switching and geographical dispersal of parasites are common phenomena, occurring on many temporal and spatial scales. Diversification involves both coevolution and colonization to explain complex host ¬ parasite associations. Across the expanse of earth history, the major radiations in parasite-host assemblages have been preceded by ecological disruption, ecological breakdown and host switching in a context that may be defined by the concept of Ecological Fitting. This cyclical process sets the stage for codiversification during periods of relative stability, punctuated by host switching during episodes of regional to global environmental disruption and climatological change. Most observed host-parasite associations can be explained by an historical interaction of Taxon Pulses (cyclical episodes of expansion and isolation in geographic range), Ecological Fitting (defining the potential for events of host colonization and initial host range), and Oscillation (episodes of increasing host range alternating with isolation on particular hosts). Major episodes of environmental change appear to be the main drivers for both persistence and diversification of host-parasite systems, creating opportunities for host switching during periods of geographic expansion and allowing for cospeciation and coadaptation during periods of relative stasis and geographic isolation. The patterns and dynamics of contemporary host-parasite associations emerge from an evolutionary context in which geographic distributions play a key role. Much of what we observe today is a legacy of that evolutionary history, and neglecting that history reduces management policies to often inadequate crisis response.

Last Modified: 4/19/2014
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