ORIGINAL PAPER Historical biogeography among species of Varestrongylus lungworms (Nematoda: Protostrongylidae) in ungulates: episodic expansion and host colonization linking Eurasia and North America Guilherme G. Verocai 1,2 & Susan J. Kutz 2 & Eric P. Hoberg 3 Received: 20 March 2018 /Accepted: 26 April 2018 # Springer-Verlag GmbH Germany, part of Springer Nature 2018 Abstract Varestrongylus lungworms (Nematoda: Protostrongylidae) include 10 nominal species that parasitize wild and domesticated artiodactyles. Eight species are endemic to the western Palearctic and Eurasia, whereas two are limited in distribution to the Nearctic. Complex host associations, primarily among Cervidae and Bovidae (Caprinae), and biogeography were explored based on direct comparisons of parasite and host phylogenies to reveal the historical development of this fauna. Diversification among Varestrongylus species has an intricate history extending over the Pliocene and Quaternary involving episodic processes for geographic and host colonization: (1) Varestrongylus has origins in Eurasia with independent expansion events into bordering ecozones; (2) cervids are ancestral hosts; (3) the caprine-associated V. pneumonicus is basal and a result of an independent host colonization event; (4) secondary diversification, linked to sequential and independent host colonization events, occurred within cervids (V. sagittatus + V. tuvae; V. alpenae; and V. capreoli, V. alces + V. eleguneniensis); (5) at least two additional host colonization events into caprines occurred, followed or not by diversification (V. qinghaiensis + V. longispiculatus; V. capricola, respectively); (6) two independent events of geographic expansion into North America from Eurasia with cervids in the late Pliocene and early Pleistocene are postulated (V. alpenae, V. eleguneniensis). Comparisons based on phylogenetic hypotheses derived from comparative morphology and molecular inference for these nematodes are consistent with the postu- lated history for coevolutionary and biogeographic history. Episodes of geographic and host colonization, often in relation to rapid shifts in climate and habitat perturbation, have dominated the history of diversification of Varestrongylus. Keywords Biogeography . Faunalassembly . Host-parasiteassociations . Metastrongyloidea . Parasitebiodiversity . Phylogenetic reconstruction Introduction Varestrongylus Bhalerao, 1932 (Nematoda; Protostrongylidae) is a monophyletic genus within the Protostrongylidae including 10 valid species among pecoran ungulates of the families Bovidae and Cervidae distributed across Eurasia and North America (Anderson 2000; Boev 1968, 1975; Dougherty and Goble 1946; Verocai 2015; Verocai et al. 2014b). Eight species are distributed in Eurasia; four of these are primarily associated with Cervidae and are distributed among Cervinae and Odocoileinae (=Capreolinae sensu (Grubb 2005 ): Varestrongylus alces Demidova & Naumitscheva, 1953 in Eurasian moose (Alces alces L.); Varestrongylus capreoli (Stroh & Schmid, 1938) in roe deer (Capreolus capreolus L.); Varestrongylus sagittatus (Mueller, 1890) primarily in red deer (Cervus elaphus L.) but also reported in fallow deer and Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00436-018-5900-0) contains supplementary material, which is available to authorized users. * Guilherme G. Verocai gverocai@gmail.com 1 Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, 510 D.W. Brooks Drive, Athens, GA 30602, USA 2 Department of Ecosystem and Public Health, Faculty of Veterinary Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada 3 Museum of Southwestern Biology, Department of Biology, University of New Mexico, Albuquerque, NM 87108, USA Parasitology Research https://doi.org/10.1007/s00436-018-5900-0