Author
 |
Hoberg, Eric |
|
Zarlenga, Dante |
|
Submitted to: Advances in Parasitology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 5/27/2016 Publication Date: 5/27/2016 Citation: Hoberg, E.P., Zarlenga, D.S. 2016. Evolution and biogeography of Haemonchus contortus, linking faunal dynamics in space and time. Advances in Parasitology. 93:1-30. Interpretive Summary: History is the foundation that informs about the nuances of faunal assembly that are essential in understanding the dynamic nature of the host-parasite interface. All of our knowledge begins and ends with evolution, ecology and biogeography as these interacting facets determine the history of biodiverse systems. We developed a historical framework surrounding these components, related to Haemonchus nematodes, among the most pathogenic among the parasites of domestic stock and wild ungulates globally. which can inform about the complex history of geographic distribution, host association, and the intricacies of the host-parasite interface that are played out in physiological and behavioral processes that influence the potential for disease and our capacity for effective control in a rapidly changing world. Origins and evolutionary radiation among species of the genus Haemonchus and Haemonchus contortus occurred in a complex crucible defined by shifts in environmental structure emerging from cycles of climate change and ecological perturbation during the late Tertiary and through the Quaternary over the past 15 million years. A history of sequential host colonization associated with waves of dispersal bringing assemblages of ungulates from Eurasia into Africa, processes of ecosystems in collision, and faunal turnover defined the arena for radiation of Haemonchus. Among species of Haemonchus, African origins and radiation in xeric to mesic habitats of the African savannah suggest that historical constraints linked to ecological adaptations (tolerances and developmental thresholds defined by temperature and humidity for larval stages) will be substantial determinants in the potential outcomes for widespread geographic and host colonization which are predicted in unfold over the coming century. This history is relevant in contemporary systems that are now strongly structured by events of invasion and colonization. On a global scale elucidating an intersection for processes of invasion and colonization in evolutionary and ecological time addresses contemporary challenges transcending interactions for responses to accelerating climate change, potential geographic colonization, and the origins, routes of dissemination and persistence for drug resistance genes at the intraspecific level in H. contortus and within species assemblages of Haemonchus. These insights about history are essential for parasitologists, disease ecologists, and veterinarians across all sectors of animal science in considering necessary steps to mitigate the advancing perturbation and impacts linked to climate change. Technical Abstract: History is the foundation that informs about the nuances of faunal assembly that are essential in understanding the dynamic nature of the host-parasite interface. All of our knowledge begins and ends with evolution, ecology and biogeography as these interacting facets determine the history of biodiverse systems. These components, related to Haemonchus, can inform about the complex history of geographic distribution, host association, and the intricacies of the host-parasite interface that are played out in physiological and behavioral processes that influence the potential for disease and our capacity for effective control in a rapidly changing world. Origins and evolutionary radiation among species of the genus Haemonchus and Haemonchus contortus occurred in a complex crucible defined by shifts in environmental structure emerging from cycles of climate change and ecological perturbation during the late Tertiary and through the Quaternary. A history of sequential host colonization associated with waves of dispersal bringing assemblages of ungulates from Eurasia into Africa, processes of ecosystems in collision, and faunal turnover defined the arena for radiation of Haemonchus. The host range for H. contortus is recognizably broad, including species among artiodactyls of 40 genera across 5 families (and within 12 tribes of Bovidae); H. contortus has an observed host range substantially greater than any congeners. An expansive host range for H. contortus is observed in endemic regions of Africa, encompassing ungulate species among 23 host genera including domestic sheep, goats and cattle. Broad host range is further dramatically reflected in the degree to which translocation, introduction and invasion with host switching, among 20 additional host genera, in North America, South America, southern Eurasia, Australia and New Zealand has characterized an expanding distribution over time, coincidental with agriculture, husbandry and global colonization by human populations especially driven by European exploration after the 1500's. It is apparent, however, that H. contortus initially emerged in association with antelopes in Africa emphasizing the importance of selection and adaptations for persistence in subtropical environments; conversely, radiation under tropical regimes would pose historical constraints for development and expansion into Temperate/Boreal and SubArctic regions. Among species of Haemonchus, African origins and radiation in xeric to mesic habitats of the African savannah suggest that historical constraints linked to ecological adaptations (tolerances and developmental thresholds defined by temperature and humidity for larval stages) will be substantial determinants in the potential outcomes for widespread geographic and host colonization which are predicted in unfold over the coming century. Limitations created by variation in moisture, humidity and pulses of precipitation (seasonally and at finer temporal and spatial scales) could be decisive in establishing permissive conditions conducive for introduction/ invasion, establishment and population amplification on the peripheries of current core distributions. As a consequence, insights about deeper evolutionary events, ecology and biogeography are critical as understanding history informs us about the possible range of responses in complex systems under new regimes of environmental forcing, especially in this case, ecological perturbation linked to climate change. This history is relevant in contemporary systems that are now strongly structured by events of invasion and colonization. On a global scale elucidating an intersection for processes of invasion and colonization in evolutionary and ecological time addresses contemporary challenges transcending interactions for responses to accelerating climate change, potential geographic colonization, and the origins, route |
