Changes to the community ecology of hosts for zoonotic pathogens, particularly rodents, are likely to influence the emergence and prevalence of zoonotic diseases worldwide. However, the complex interactions between abiotic factors, pathogens, vectors, hosts, and both food resources and predators of hosts are difficult to disentangle. Here we (1) use 19 yr of data from six large field plots in southeastern New York to compare the effects of hypothesized drivers of interannual variation in Lyme disease risk, including the abundance of acorns, rodents, and deer, as well as a series of climate variables; and (2) employ landscape epidemiology to explore how variation in predator community structure and forest cover influences spatial variation in the infection prevalence of ticks for the Lyme disease bacterium, Borrelia burgdorferi, and two other important tick-borne pathogens, Anaplasma phagocytophilum and Babesia microti. Acorn-driven increases in the abundance of mice were correlated with a lagged increase in the abundance of questing nymph-stage Ixodes scapularis ticks infected with Lyme disease bacteria. Abundance of white-tailed deer 2 yr prior also correlated with increased density of infected nymphal ticks, although the effect was weak. Density of rodents in the current year was a strong negative predictor of nymph density, apparently because high current abundance of these hosts can remove nymphs from the host-seeking population. Warm, dry spring or winter weather was associated with reduced density of infected nymphs. At the landscape scale, the presence of functionally diverse predator communities or of bobcats, the only obligate carnivore, was associated with reduced infection prevalence of I. scapularis nymphs with all three zoonotic pathogens. In the case of Lyme disease, infection prevalence increased where coyotes were present but smaller predators were displaced or otherwise absent. For all pathogens, infection prevalence was lowest when forest cover within a 1 km radius was high. Taken together, our results suggest that a food web perspective including bottom-up and top-down forcing is needed to understand drivers of tick-borne disease risk, a result that may also apply to other rodent-borne zoonoses. Prevention of exposure based on ecological indicators of heightened risk should help protect public health.

Tick-borne disease risk in a forest food web.

Space use and diets of sympatric bobcats Lynx rufus and pumas Puma concolor were compared using sign surveys and scat analysis during 1997–2002 in south-eastern Arizona, USA. Bobcats appeared to use grassland, scrub, riparian and woodland habitats equally, but pumas had higher activity in riparian and woodland habitats. There was little evidence that bobcats avoided pumas in space use. Bobcats ate primarily rodents (33% of items in scats), lagomorphs (32%) and ungulates (16%), whereas pumas ate primarily ungulates (69%) and carnivores (21%). Pumas had a narrower dietary niche breadth than bobcats, and puma diet overlapped bobcat diet by 56%, suggesting that pumas may be more vulnerable to changes in prey density than bobcats. Pumas also killed and consumed bobcats, indicating that interference competition may be manifesting through intraguild predation.

Competition and coexistence in sympatric bobcats and pumas

Aim
Phylogenetic niche conservatism (PNC), a pattern of closely related species retaining ancestral niche-related traits over evolutionary time, is well documented for abiotic (Grinellian) dimensions of the ecological niche. However, it remains unclear whether biotic niche (Eltonian) axes are also phylogenetically conserved, even though knowledge of biotic niches is essential to an understanding of the spatiotemporal dynamics of ecological communities. We conduct the first analysis of biotic PNC by evaluating dietary specialization in a vertebrate class. 

Location 
Global

Methods 
We analysed two global compilations of diets of living mammals and a more detailed database for large carnivores together with a species-level phylogeny to evaluate trophic PNC. We searched for evidence of PNC by estimating the phylogenetic signal in distinct descriptors of dietary niche. 

Results 
Trophic niches were generally similar among related species but not strongly conserved under a niche-drift macroevolutionary model (Brownian Motion). The degree of similarity in trophic niche varied among different taxonomic groups and was, importantly, even within the same group, contingent on the metric of dietary preferences used and the quality of information on the database. 

Main conclusions 
Overall, our results showed limited support for PNC in the trophic niche of mammals. However, different data sources and metrics of dietary preferences sometimes offered different conclusions, highlighting the importance of gathering high-quality quantitative data and considering multiple metrics to describe dietary niche breadth and to assess PNC. The fully quantitative database for large carnivores provided some interesting evidence of PNC that could not be detected with semi-quantitative or presence/absence descriptors. Subsequent assessments of phylogenetic imprints on dietary specialization would benefit from considering different metrics and using well-resolved phylogenies jointly with detailed quantitative diet information. While Eltonian trophic niches did not show the same high levels of evolutionary conservatism often displayed by Grinnellian niches, both niche components should be considered to understand range limits of species and clades at biogeographic scales.

/pdf/contrasting-evidence-of-phylogenetic-trophic-niche-vzxakppjxj.pdf

Contrasting evidence of phylogenetic trophic niche conservatism in mammals worldwide

Epidemiology of toxoplasmosis in white tailed deer (Odocoileus virginianus): occurrence, congenital transmission, correlates of infection, isolation, and genetic characterization of Toxoplasma gondii.

From 2000 to 2002 bobcat blood samples were collected, in association with the Pennsylvania Game Commission, during the recently reactivated bobcat hunting and trapping season. Sex, age, and county/township data were recorded for each animal. Blood was tested for antibodies to Toxoplasma gondii using the modified agglutination test. In the 2-yr study, 131 bobcat samples were collected in 14 Pennsylvania counties and 109 (83%) of these had antibodies to T. gondii (titer≥25). A two-way Chi-Square test (95% confidence interval) yielded no significance differences in antibody prevalence between males (83%) and females (88%) or adults (83%) and juveniles (77%). All 14 counties had at least one bobcat with antibodies to T. gondii.

https://bioone.org/journals/journal-of-wildlife-diseases/volume-42/issue-1/0090-3558-42.1.188/Seroprevalence-of-Antibodies-to-Toxoplasma-gondii-in-the-Pennsylvania-Bobcat/10.7589/0090-3558-42.1.188.pdf

Seroprevalence of antibodies to Toxoplasma gondii in the Pennsylvania bobcat (Lynx rufus rufus).

Diet of the bobcat (Lynx rufus) in the mid-Atlantic region of the United States is poorly known. Age, sex and time of year are thought to influence bobcat prey selection, but accounts vary. We examined the contents of 85 bobcat stomachs taken from Pennsylvania during autumn and winter 2000–2002. White-tailed deer (Odocoileus virginianus) and rabbits (Sylvilagus sp.) occurred most frequently as prey. A larger percentage of female bobcats consumed lagomorphs (28%) than did males (12%; P = 0.04). More male bobcats consumed meso-mammals (14%), including raccoons and porcupines, than did females (2%; P = 0.04). Diet did not differ between bobcats <2 y and bobcats ≥2 y. Variety of prey eaten was larger in autumn than in winter. Sexual differences in diet may be related to sexual dimorphism in this species and may help to effect interspecific niche partitioning. Winter weather reduces the availability of certain prey items in this region and may decrease the bobcat's ability to travel and hunt effectively.

https://bioone.org/journals/the-american-midland-naturalist/volume-153/issue-2/0003-0031(2005)153[0450:IOASAT]2.0.CO;2/Influence-of-Age-Sex-and-Time-of-Year-on-Diet/10.1674/0003-0031(2005)153[0450:IOASAT]2.0.CO;2.pdf

Meredith L. McLEAN

Papers

Influence of Age, Sex and Time of Year on Diet of the Bobcat (Lynx rufus) in Pennsylvania