Rodent–Pika Parasite Spillover in Western North America

Abstract

Competition during the Cenozoic expansion of the Rodentia may have contributed to ecological niche reduction of pikas, which are now increasingly under threat as their habitat degrades under global climate change, while some rodents expand their ranges and overlap with pikas. Range overlap carries the possibility of disease spillover. Contemporary North American pikas are cold-adapted and relegated primarily to alpine environments where they subsist on relatively low-quality herbaceous diet. Yet their evolutionary ancestors were distributed geographically even into the subtropics. Here we examine historical and contemporary records of fleas on pikas (Ochotona princeps) from sites at different elevations in the Sierra Nevada and Rocky Mountains and the Pacific Northwest. We calculated indices of diversity from each site and spillover fraction, i.e., the proportion of fleas on pikas that have a preference for rodents. Across this range there are four pika specialist flea species, with no more than two of these per site, and 18 characteristically rodent flea species. Diversity is greatest in the Pacific Northwest and lowest in Montana. Rodent flea spillover onto pikas declines with elevation in the Rocky Mountains. These data provide evidence that rodents and pikas interact enough to allow considerable parasite spillover, and which could be exacerbated as pikas are increasingly stressed by climate change at lower elevations some rodent species expand up-elevation in the face of increasing global warming. With global climate change, both biotic and abiotic niche shrinkage demand our attention.

An Assemblage of Fleas (Siphonaptera) From Canada, México, and the United States of America, in the Hastriter Collecton (Brigham Young University)

“…Aetheca wagneri Haddow et al 1983:43 (Central to western U.S.A.), Lewis et al 1988:160–161 (CA, NV, OR, WA), Galloway and Christie 1990:455 (MB), Baird and Saunders 1992:12–13 (ID), Linley, et al 1994:815–817, Larson et al 1996:35 (CA), Ponce-Ulloa and Llorente-Bousquets 1996:561 (México), Larson 1997:3 (ND), Lindsay and Galloway 1997:1313 (MB), Fagelund et al 2001:94 (NM), Smith and Belthoff 2001:160 (ID), Davis et al 2002:110–111 (CA), Ford et al 2004:51–53 (NM), Haas and Kucera 2004:349 (UT), Haas et al (2004:514 (NM), Krasnov et al 2004a:234, 2004b:514, Bossard 2006:262, 264 (none), Morrone and Acosta 2006:2 (México), Foley et al 2017:1253 (none), Bergman et al 2019:18 (BC).…”

“…Amaradix bitterrootensis Baird and Saunders 1992:13 (ID), Ford et al 2004:37 (NM), Foley et al 2017:1252–1253 (CO).…”

Ecology and Management of Plague in Diverse Communities of Rodents and Fleas

“…Marmots are heavily involved in plague cycles in central Asia, perhaps in polyhostal systems with ground squirrels, voles, and Ochotona pikas (Kalabukhov 1965). Unfortunately, the importance of plague in marmots in the western United States of America has been little studied, but the possibility exists that T. acamantis in high elevation sites may assist in cycling Y. pestis among marmots, PDs, other rodents, and additional hosts, including American pikas (O. princeps), the latter of which are known to carry T. acamantis (Foley et al 2017) and have declined considerably in abundance, perhaps due to plague (Wilkening et al 2011).…”

Northeastern California plateaus bioregion science synthesis

“…However, as pika distributions are moving, often uphill, in response to a warming climate, so are other rodent species, and with those species come new disease threats that pikas have not been exposed to previously. Foley et al (2017) have shown that in high-elevation sites in Colorado and Montana, the diversity of flea species found on pikas includes species that specialize on pikas as well as species that specialize on other rodent species, presumably from contact with those other rodent species.…”