Esa Koskela | University of Jyväskylä (original) (raw)

Papers by Esa Koskela

The impact of a pathogen on the fitness and behaviour of its natural host depends upon the host–p... more The impact of a pathogen on the fitness and behaviour of its natural host depends upon the host–parasite relationship in a given set of environmental conditions. Here, we experimentally investigated the effects of Borrelia afzelii, one of the etiological agents of Lyme disease in humans, on the fitness of its natural rodent host, the bank vole (Myodes glareolus), in semi-natural conditions with two contrasting host population densities. Our results show that B. afzelii can modify the reproductive success and spacing behaviour of its rodent host, whereas host survival was not affected. Infection impaired the breeding probability of large bank voles. Reproduction was hastened in infected females without alteration of the offspring size at birth. At low density, infected males produced fewer offspring, fertilized fewer females and had lower mobility than uninfected individuals. Meanwhile, the infection did not affect the proportion of offspring produced or the proportion of mating partner in female bank voles. Our study is the first to show that B. afzelii infection alters the reproductive success of the natural host. The effects observed can reflect the sickness behaviour due to the infection or they can be a consequence of a manipulation of the host behaviour by the bacteria.

The loci arginine vasopressin receptor 1a (avpr1a) and oxytocin receptor (<... more The loci arginine vasopressin receptor 1a (avpr1a) and oxytocin receptor (oxtr) have evolutionarily conserved roles in vertebrate social and sexual behaviour. Allelic variation at a microsatellite locus in the 5′ regulatory region of these genes is associated with fitness in the bank vole Myodes glareolus. Given the low frequency of long and short alleles at these microsatellite loci in wild bank voles, we used breeding trials to determine whether selection acts against long and short alleles. Female bank voles with intermediate length avpr1a alleles had the highest probability of breeding, while male voles whose avpr1a alleles were very different in length had reduced probability of breeding. Moreover, there was a significant interaction between male and female oxtr genotypes, where potential breeding pairs with dissimilar length alleles had reduced probability of breeding. These data show how genetic variation at microsatellite loci associated with avpr1a and oxtr is associated with fitness, and highlight complex patterns of selection at these loci. More widely, these data show how stabilizing selection might act on allele length frequency distributions at gene-associated microsatellite loci.

Average monthly saturation deficit and temperature during the monitoring years. Figure S2. Observ... more Average monthly saturation deficit and temperature during the monitoring years. Figure S2. Observed mean abundance of ticks in vegetation per session, from May 2012 to October 2015. Figure S3. Mean number of vole captured per trap-night at each session and in each site, from May 2012 to October 2015. Table S1. Selection table for models explaining the abundance of ticks questing in the vegetation. Figure S4. Predicted number of larvae, nymphs and pooled nymphs and females per 100Â m2 of vegetation explained by bank vole abundance. Table S2. Selection table for models explaining the abundance of ticks questing in the vegetation. Table S3. Total number of ticks (per species and stage) collected on voles. Figure S5. Vole infestation per session with I. ricinus larvae and nymphs from May 2012 to October 2015. Table S4. Selection table for models explaining the abundance of infesting larvae. Table S5. Selection table for models explaining the abundance of infesting nymphs. Table S6. Additional model for the abundance of nymphs questing in the vegetation. Table S7. Selection table for the additional model explaining the abundance of questing nymphs. (DOCX 3706 kb)

The American Naturalist, Aug 1, 2018

This is a self-archived version of an original article. This version may differ from the original... more This is a self-archived version of an original article. This version may differ from the original in pagination and typographic details.

Proceedings of The Royal Society B: Biological Sciences, Dec 13, 2017

The loci arginine vasopressin receptor 1a (avpr1a) and oxytocin receptor (oxtr) have evolutionari... more The loci arginine vasopressin receptor 1a (avpr1a) and oxytocin receptor (oxtr) have evolutionarily conserved roles in vertebrate social and sexual behaviour. Allelic variation at a microsatellite locus in the 5 0 regulatory region of these genes is associated with fitness in the bank vole Myodes glareolus. Given the low frequency of long and short alleles at these microsatellite loci in wild bank voles, we used breeding trials to determine whether selection acts against long and short alleles. Female bank voles with intermediate length avpr1a alleles had the highest probability of breeding, while male voles whose avpr1a alleles were very different in length had reduced probability of breeding. Moreover, there was a significant interaction between male and female oxtr genotypes, where potential breeding pairs with dissimilar length alleles had reduced probability of breeding. These data show how genetic variation at microsatellite loci associated with avpr1a and oxtr is associated with fitness, and highlight complex patterns of selection at these loci. More widely, these data show how stabilizing selection might act on allele length frequency distributions at gene-associated microsatellite loci.

Parasites & Vectors, Mar 31, 2017

Background: Tick-borne pathogens pose an increasing threat to human and veterinary health across ... more Background: Tick-borne pathogens pose an increasing threat to human and veterinary health across the northern hemisphere. While the seasonal activity of ticks is largely determined by climatic conditions, host-population dynamics are also likely to affect tick abundance. Consequently, abundance fluctuations of rodents in northern Europe are expected to be translated into tick dynamics, and can hence potentially affect the circulation of tick-borne pathogens. We quantified and explained the temporal dynamics of the tick Ixodes ricinus in the northernmost part of its European geographical range, by estimating (i) abundance in vegetation and (ii) infestation load in the most common rodent species in the study area, the bank vole Myodes glareolus. Results: Ixodes ricinus nymphs and adult females, the life stages responsible for the most of tick bites in humans, peaked in May-June and August-September. Larvae and nymphs were simultaneously active in June and abundance of questing larvae and nymphs in the vegetation showed a positive association with bank vole abundance. Moreover, infesting larvae and nymphs were aggregated on bank voles, and the infestation of bank voles with I. ricinus larvae and nymphs was positively associated with bank vole abundance. Conclusion: Our results indicate early summer and early autumn as periods of increased risk for humans to encounter I. ricinus ticks in boreal urban forests and suggest a 2 years life-cycle for I. ricinus with two cohorts of ticks during the same year. Moreover, we identified a simultaneous activity of larvae and nymphs which allows co-feeding on the rodent host, which in turn supports the transmission of several important zoonotic tick-borne pathogens. Finally, we showed that a high density of the rodent host may enhance the risk that ticks and, potentially, tick-borne pathogens pose to human health.

Oecologia, Dec 28, 2020

Most small rodent populations in the world have fascinating population dynamics. In the northern ... more Most small rodent populations in the world have fascinating population dynamics. In the northern hemisphere, voles and lemmings tend to show population cycles with regular fluctuations in numbers. In the southern hemisphere, small rodents tend to have large amplitude outbreaks with less regular intervals. In the light of vast research and debate over almost a century, we here discuss the driving forces of these different rodent population dynamics. We highlight ten questions directly related to the various characteristics of relevant populations and ecosystems that still need to be answered. This overview is not intended as a complete list of questions but rather focuses on the most important issues that are essential for understanding the generality of small rodent population dynamics.

Proceedings of The Royal Society B: Biological Sciences, Jun 22, 1998

Food limitation has been suggested as one of the most important factors a¡ecting life-history evo... more Food limitation has been suggested as one of the most important factors a¡ecting life-history evolution in terrestrial vertebrates. However, this inference is based mainly on evidence from birds, and reproductive trade-o¡s may di¡er among groups with di¡erent forms of parental care. To study whether the costs of enlarged litters (decreased mass of o¡spring) would appear when food is not limiting, we performed outdoor enclosure experiments in which we manipulated simultaneously the litter size (control versus +two pups) and food availability (control versus food-supplemented) of female bank voles, Clethrionomys glareolus. The weaning success of females increased signi¢cantly in response to supplementary food. When females were provided with extra food, no di¡erences were observed in the body masses of weanlings of control and enlarged litters. Further, food-supplemented females grew to larger sizes during nursing than unsupplemented females. Our experiment suggests that energetic requirements during nursing constrain the number of o¡spring that can be successfully raised in a particular breeding attempt. The results also indicate that unlimiting food resources may increase future reproductive potential of females, because they can use more energy for somatic growth.

Journal of Animal Ecology, Jun 20, 2019

Routledge eBooks, Jun 15, 2023

Ecosystem degradation decreases planetary well-being Properly functioning ecosystems support dive... more Ecosystem degradation decreases planetary well-being Properly functioning ecosystems support diverse processes that sustain life, ranging from climate regulation and oxygen production to maintaining biodiversity. Ahealthyecosystemmaybedefinedasasustainableandresilientsystemthatmaintains its function despite external stress (Costanza and Mageau, 1999). A healthy ecosystem provides key services to its biota, and disturbances to the system may impact the health and/or abundance of key members of its assemblage, such that they can no longer perform their ecological roles. In this chapter, we discuss the cascading effects that ecosystem degradation has on the health of wildlife, humans, and entire ecosystems and the consequent threat to planetary well-being. Overexploitation of natural resources by humans has resulted in widespread ecosystem degradation: More than half of all ecosystems on Earth have deteriorated because of human actions (Myers, 2017; Song et al., 2018). This degradation has negatively impacted a range of ecological functions with notable adverse consequences for the well-being of wildlife (undomesticated animals and plants inhabiting natural environments) and humans. Environmental change has, for example, directly increased infectious disease prevalence in humans and other organisms by facilitating the spread of invasive species, disease vectors (organisms that carry and transmit pathogens to other organisms), and pathogens (Parmesan and Yohe, 2003). The interplay between ecosystem, human, and nonhuman health is recognized by several well-established health-related concepts, such as Conservation Medicine (

Molecular Ecology

Anthropogenic changes to land use drive concomitant changes in biodiversity, including that of th... more Anthropogenic changes to land use drive concomitant changes in biodiversity, including that of the soil microbiota. However, it is not clear how increasing intensity of human disturbance is reflected in the soil microbial communities. To address this issue, we used amplicon sequencing to quantify the microbiota (bacteria and fungi) in the soil of forests (n = 312) experiencing four different land uses, national parks (set aside for nature conservation), managed (for forestry purposes), suburban (on the border of an urban area) and urban (fully within a town or city), which broadly represent a gradient of anthropogenic disturbance. Alpha diversity of bacteria and fungi increased with increasing levels of anthropogenic disturbance, and was thus highest in urban forest soils and lowest in the national parks. The forest soil microbial communities were structured according to the level of anthropogenic disturbance, with a clear urban signature evident in both bacteria and fungi. Despite ...

Proceedings of the Royal Society B: Biological Sciences

The diet of an individual is a result of the availability of dietary items and the individual&#39... more The diet of an individual is a result of the availability of dietary items and the individual's foraging skills and preferences. Behavioural differences may thus influence diet variation, but the evolvability of diet choice through behavioural evolution has not been studied. We used experimental evolution combined with a field enclosure experiment to test whether behavioural selection leads to dietary divergence. We analysed the individual dietary niche via stable isotope ratios of nitrogen ( δ 15 N) and carbon ( δ 13 C) in the hair of an omnivorous mammal, the bank vole, from four lines selected for predatory behaviour and four unselected control lines. Predatory voles had higher hair δ 15 N values than control voles, supporting our hypothesis that predatory voles would consume a higher trophic level diet (more animal versus plant foods). This difference was significant in the early but not the late summer season. The δ 13 C values also indicated a seasonal change in the consum...

The data contains vole trapping indices for each spring and autumn from multiple sites across Fin... more The data contains vole trapping indices for each spring and autumn from multiple sites across Finland, abundance indices for small mustelids and generalist mammalian predators (data from Finnish wildlilfe triangle scheme, averaged for each vole trapping site), and avian predator abundance indices (data from the Finnish Bord Ringing Office, averaged for each vole trapping site)

Data on field captured female bank voles (n=890) to examine the breeding probability (BRED: 0=no,... more Data on field captured female bank voles (n=890) to examine the breeding probability (BRED: 0=no, 1=yes) including individual information PUUV infection status of the female (PUUV_INF: 0=uninfected, 1=infected) and head with (centred value over given period of breeding season), and population level information; the period of breeding season (season: 1=early, 2=mid, 3=late), the phase of vole cycle (cycle: 1= low phase, 2=increase phase, 3= peak phase) and random effect (random)