Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/8/2010
Publication Date: 6/1/2010
Citation: Durette-Desset, M.C., Galbreath, K.E., Hoberg, E.P. 2010. Discovery of new Ohbayashinema spp. (nematoda: heligomosomoidea) in Ochotona princeps and O. cansus (lagomorpha: ochotonidae) from western North America and central Asia, with considerations of historical biogeography. Journal of Parasitology. 96:569-579. Interpretive Summary: Definitions for patterns of parasite diversity (numbers of species, and their host and geographic distributions) are important cornerstones in understanding and predicting responses of complex host-pathogen systems to environmental change. Using the combined resources of the US National Parasite Collection and new extensive field-based surveys in western North America and China, we describe 3 new species of nematodes in the genus Ohbayashinema which are parasites of small lagomorphs. Species of Ohbayashinema appear to be host-specific (are limited in their occurrence to a particular group of vertebrate hosts) among the Ochotonidae or pikas, but had not been previously reported from localities in North America. Although much remains to be demonstrated about the diversity for helminths in pikas, it is apparent that factors associated with the assembly and structure of parasite faunas have been complex, involving episodic processes for geographic and host colonization along with coevolutionary mechanisms. Studies of Ohbayashinema contribute to a growing body of work which identifies climate change as an important factor that has influenced the evolution and distribution of pathogens. Historical factors, particularly climate-driven fluctuations in geographic range for hosts have structured these faunas. Pikas, their parasites and other vertebrates including some free-ranging ungulates are linked to increasingly isolated sky-island habitats in the Intermountain west of North America. Habitat modification and landscape fragmentation under the current regime for global warming has considerable implications for the continuity of already localized assemblages of hosts and parasites in these areas. Integrated studies of populations and species of hosts and parasites contribute baselines for identifying responses of complex biological systems under directional climate warming.
Technical Abstract: Three new species of Ohbayashinema (Nematoda, Heligmosomoidea) are described from localities in western North America and central Asia. Two of these species, Ohbayashinema nearctica n. sp and O. aspeira n. sp. are parasitic in American pika, Ochotona princeps. Ohbayashinema nearctica is differentiated from the five known species of the genus parasitic in Ochotonidae from the Old World by very long spicules and an oblique axis of orientation for the ridges composing the synlophe. Ohbayashinema aspeira, only described from females, is similar to O. nearctica based on the number of cuticular ridges at the mid-body. It is mainly differentiated by an uncoiled anterior extremity and by near equal dimensions of the vestibule and the uterus. The third species, O. patriciae n. sp., is parasitic in Gansu pika, Ochotona cansus from China. It is similar to O. erbaevae parasitic in Ochotona dauurica from Buriatia and O. ochotoni in Ochotona macrotis from Nepal, based on the length of the spicules and the ratio of spicule length to body length. It differs from the former species by possessing a smaller number of cuticular ridges and in the comparative length of the vestibule and infundibulum. Related to O. ochotoni by an identical number of cuticular ridges at the mid-body, it differs from this species in having smaller ridges in the dorsal rather than ventral field and in the dimensions of the dorsal rays where rays 9 < rays 10. Species of Ohbayashinema appear to be host-specific among the Ochotonidae, but had not been previously reported in pikas from the Nearctic. Although much remains to be demonstrated about the diversity for helminths in pikas, it is apparent that factors associated with the assembly and structure of parasite faunas have been complex, involving episodic processes for geographic and host colonization along with coevolutionary mechanisms. Understanding the historical factors, particularly climate-driven fluctuations in geographic range that have structured these faunas, suggests that the current regime for global warming and habitat modification has considerable implications for the continuity of already localized assemblages of hosts and parasites.