Range-wide Determinants of Plague Distribution in North America

Abstract

Abstract. Plague, caused by the bacterium Yersinia pestis , is established across western North America, and yet little is known of what determines the broad-scale dimensions of its overall range. We tested whether its North American distribution represents a composite of individual host-plague associations (the "Host Niche Hypothesis"), or whether mammal hosts become infected only at sites overlapping ecological conditions appropriate for plague transmission and maintenance (the "Plague Niche Hypothesis"). We took advantage of a novel data set summarizing plague records in wild mammals newly digitized from paper-based records at the Centers for Disease Control and Prevention to develop range-wide tests of ecological niche similarity between mammal host niches and plague-infected host niches. Results indicate that plague infections occur under circumstances distinct from the broader ecological distribution of hosts, and that plagueinfected niches are similar among hosts; hence, evidence coincides with the predictions of the Plague Niche Hypothesis, and contrasts with those of the Host Niche Hypothesis. The "plague niche" is likely driven by ecological requirements of vector flea species.

Epidemiology of Human Plague in the United States, 1900–2012

“…on the outskirts of the city by 1908 ( 3 ). In contrast, Y. pestis apparently never successfully established in wild rodent populations outside of Gulf coast port cities, likely a result of inhospitable ecology and early and extensive urban rat control efforts ( 3 , 5 , 8 ). …”

“…This distribution has remained static for >60 years, presumably the result of climatic and ecologic factors that limit further spread ( 3 , 5 – 9 ). Although poorly defined, these factors may be related to the ecology of vector species rather than that of rodent hosts ( 8 ). …”

Range‐wide ecological niche comparisons of parasite, hosts and dispersers in a vector‐borne plant parasite system

“…Grey polygons in the upper panel show a mosaic of host or vector niches; in the lower panel, the grey polygon shows the parasite's niche and dashed outlines show the niches of hosts and/or vectors. (Figure modified from Maher et al ., . )…”

Accessible areas in ecological niche comparisons of invasive species: Recognized but still overlooked

“…Using ENMs to generate potential distribution estimates for each population or species, calculating some level of niche similarity, and comparing to a null distribution of expectations are typical steps that recent studies have followed [13][14][15][16] . However, the premise for comparing two ENMs is that both are distributed across the same or similar regions; that is, in cases in which available environmental conditions differ absolutely between the species being compared, tests will either be inconclusive or will reach incorrect conclusions 3 .…”