Influences of introduced plague on North American mammals: Implications from ecology of plague in Asia

Intercontinental movements of invasive species continue to modify the world 's ecosystems. The plague bacterium (Yersinia pestis) has colonized and alt ered animal communities worldwide but has received much more attention as a human pathogen. We reviewed studies on the ecology of Y. pestis in ancient foci of central Asia and in western North America, where the bacterium app arently has become established much more recently. Although rodent populati ons on both continents are affected dramatically by epizootics of plague, t he epidemiologically important species of Asia demonstrate resistance in po rtions of their populations, whereas those of North America are highly susc eptible. Individual variation in resistance, which is widespread in Asian r odents and allows a microevolutionary response, has been documented in few North American species of rodents. Plague increases costs of sociality and coloniality in susceptible hosts, increases benefits of disease resistance in general, and increases benefits of adaptability to variable environments for species at higher trophic levels. Prairie dogs (Cynomys) epitomize tax a with high risk to plague because prairie dogs have uniformly low resistan ce to plague and are highly social. Relationships to plague are poorly unde rstood for many North American rodents, but more than one-half of the speci es of conservation concern occur within the geographic range of plague.