Biology subjects

Mappes, T.

Publications and source records attributed to Mappes, T..

3 recordsLinked to original sources

bioRxiv2025

Contrasting roles of host species in tick-pathogen interactions and their influence on Lyme borreliosis hazard across boreal island communities

Predicting the hazard of Lyme borreliosis (LB) is complex due to host-specific effects on tick and pathogen dynamics. To unpick the contributions of cervids and rodents on ticks and Borrelia burgdorferi infection in ticks in boreal region, we analysed data from 41 islands in Finland (2017-2021) with considerable natural variation in the abundances of cervids and rodents, and densities of nymphs (DON: 0-82.5 nymphs/100 m2), nymph infection prevalences (NIP: 0-60%) and densities of infected nymphs (DIN: 0-16.5/100 m2). Using structural equation modelling (SEM), we disentangled direct and indirect effects of host abundances on LB hazard (i.e., DIN). Rodent abundance was associated with higher DIN through its positive effect on NIP (pathogen amplification), while showing no effect on DON. Cervids increased DON (vector amplification) but decreased NIP (pathogen dilution). Our study suggests that in boreal forests the vectors may be supported by very low cervid densities and, as a virtual absence of rodents did not eliminate the pathogen, the pathogen is likely to persist through very low rodent densities. Our study highlights how islands function as a natural mesocosm for rigorous field studies of complex ecological interactions and SEM can serve as a powerful tool to reveal mechanisms driving LB hazard.

ecology↗

bioRxiv2024

Covariation between metabolic and radioactive dose rates in Chornobyl rodents

High metabolic rate may provide fitness benefits for individuals. But high metabolic rates incur energetic costs and the need to ingest more food, increasing the risks of ingesting harmful substances from the environment. How organisms respond to elevated levels of ionizing radiation is an important question in the light of increasing pollution from nuclear accidents and waste, as well as ever-increasing reliance on radiation in medical diagnostics and therapies. We investigated how limits to metabolic rate, and aerobic metabolic scope (ceiling of energetic activity above maintenance levels), of wild rodents inhabiting a gradient of radioactive contamination from the Chernobyl accident covary with the biological burden of radionuclides in their bodies. Our results demonstrate that high biological dose rate correlates with high self-maintenance and low aerobic capacity in adults. In contrast, in subadults high dose rate correlates with high aerobic capacity. Consequently, high dose rate correlates with low aerobic scope in adults, but with high aerobic scope in subadults. Despite the uncertainty of the causal mechanisms, whether the dose rate affects the metabolic rate, the reverse or the reciprocal feedback prevail, it can be hypothesized that metabolic down-regulation could contribute to protection against radioactive exposure. Yet, metabolic down-regulation might be constrained by developmental obligations. Understanding the physiological mechanisms affecting responses to radiation exposure is key for risk assessment of environmental contamination, radiotherapies, and space exploration, and may help to rectify discordant opinions concerning the effects of radiation on the ecology of organisms living in Chornobyl.

ecology↗

bioRxiv2021

Artificial selection for predatory behavior results in dietary niche differentiation in an omnivorous mammal

The diet of an individual is a result of the availability of dietary items and the individuals foraging skills and preferences. Behavioral differences may thus influence diet variation, but the evolvability of diet choice through behavioral evolution has not been studied. We used experimental evolution combined with a field enclosure experiment to test whether behavioral selection leads to dietary divergence. We analysed the individual dietary niche via stable isotope ratios of nitrogen ({delta}15N) and carbon ({delta}13C) in the hair of an omnivorous mammal, bank vole, from 4 lines selected for predatory behavior and 4 unselected control lines. Predatory voles had higher hair {delta}15N values than control voles, supporting our hypothesis that predatory voles would consume a higher trophic level diet (more animal vs. plant foods). This difference was significant in the early but not the late summer season. The {delta}13C values also indicated a seasonal change in the consumed plant matter and a difference in food sources among selection lines in the early summer. These results imply that environmental factors interact with evolved behavioral tendencies to determine dietary niche heterogeneity. Behavioral selection thus has potential to contribute to the evolution of diet choice and ultimately the species ecological niche breadth.

ecology↗