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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 notable differences in community composition, there was little change in the predicted functional traits of urban bacteria. By contrast, urban soils exhibited a marked loss of ectomycorrhizal fungi. Soil pH was positively correlated with the level of disturbance, and thus was the strongest predictor of variation in alpha and beta diversity of forest soil communities, indicating a role of soil alkalinity in structuring urban soil microbial communities. Hence, our study shows how the properties of urban forest soils promote an increase in microbial diversity and a change in forest soil microbiota composition. [ABSTRACT FROM AUTHOR]

The early life environment can have profound, long‐lasting effects on an individual's fitness. For example, early life quality might (a) positively associate with fitness (a silver spoon effect), (b) stimulate a predictive adaptive response (by adjusting the phenotype to the quality of the environment to maximize fitness) or (c) be obscured by subsequent plasticity. Potentially, the effects of the early life environment can persist beyond one generation, though the intergenerational plasticity on fitness traits of a subsequent generation is unclear.To study both intra‐ and intergenerational effects of the early life environment, we exposed a first generation of bank voles to two early life stimuli (variation in food and social environment) in a controlled environment. To assess possible intra‐generational effects, the reproductive success of female individuals was investigated by placing them in large outdoor enclosures in two different, ecologically relevant environments (population densities).Resulting offspring were raised in the same population densities where they were conceived and their growth was recorded. When adult, half of the offspring were transferred to opposite population densities to evaluate their winter survival, a crucial fitness trait for bank voles.Our setup allowed us to assess: (a) do early life population density cues elicit an intra‐generational adaptive response, that is a higher reproductive success when the density matches the early life cues and (b) can early life stimuli of one generation elicit an intergenerational adaptive response in their offspring, that is a higher growth and winter survival when the density matches the early life cues of their mother.Our results show that the early life environment directly affects the phenotype and reproductive success of the focal generation, but adaptive responses are only evident in the offspring. Growth of the offspring is maintained only when the environment matches their mother's early life environment. Furthermore, winter survival of offspring also tended to be higher in high population densities if their mothers experienced an competitive early life. These results show that the early life environment can contribute to maintain high fitness in challenging environments, but not necessarily in the generation experiencing the early life cues. [ABSTRACT FROM AUTHOR]

Variation in dominance status determines male mating and reproductive success, but natural selection for male dominance can be detrimental or antagonistic for female performance, and ultimately their fitness. Attaining and maintaining a high dominance status in a population of competing individuals is physiologically costly for males. But how male dominance status is mediated by maintenance energetics is currently not well understood, nor are the corresponding effects of male energetics on his sisters recognized.We conducted laboratory and field experiments on rodent populations to test whether selective breeding for male dominance status (dominant vs. subordinate breeding lines) antagonistically affected basal metabolic rate (BMR) and fitness of females under wild conditions.Our results showed elevated BMR in females, but not in males, from the dominant breeding line. However, phenotypically dominant males from the subordinate breeding line had the highest BMR.Males from the dominant line with low BMR sired the most litters and offspring in the field. Similarly, females from the dominant selection line tended to have more offspring if they had lower BMR, while the opposite trend was found in females from the subordinate selection line. Females with high and low BMR reproduced most often, as indicated by a significant quadratic selection gradient.The increased female BMR resulting from selection for male dominance suggests genetic incompatibility between sexes in metabolism inheritance. Elevated BMR in behaviourally dominant males, but not in males from the dominant breeding line, suggests physiological costs in males not genetically suited for dominance.Fitness costs of elevated maintenance costs (measured as BMR) shown here support the energetic compensation hypothesis where high BMR is selected against as it would trade off energy required for other important life‐history attributes. A plain language summary is available for this article. Plain Language Summary [ABSTRACT FROM AUTHOR]

Pathogens often cause detrimental effects to their hosts and, consequently, may influence host population dynamics that may, in turn, feed back to pathogen transmission dynamics. Understanding fitness effects of pathogens upon animal host populations can help to predict the risks that zoonotic pathogens pose to humans., Here we determine whether chronic infection by Puumala hantavirus ( PUUV) affects important fitness-related traits, namely the probability of breeding, reproductive effort and mother and offspring condition, in the bank vole ( Myodes glareolus). Using 9 years empirical data in a PUUV endemic area in Central Finland, we found differences between reproductive characteristics of PUUV-infected and uninfected female bank voles., Young infected females had a significantly higher, and old individuals lower, likelihood of reproducing than uninfected animals during the middle of the breeding season. The implication is that PUUV infection may have long-term deleterious effects that are observed at old age, while in young individuals, the infection may enhance breeding probability by directing resources towards current breeding., Moreover, PUUV infection was related with the mother's body condition. Infected mothers were in poorer condition than uninfected mothers in the early breeding season, but were in better condition than uninfected mothers during the middle of the breeding season. Offspring body condition was positively associated with mother's body condition, which, in turn, was related to the PUUV infection status of the mother., Our findings indicate that chronic infection may affect the reproduction of female hosts, but the effect is dependent on the host age. The effect of chronic hantavirus infection was small and density-independent and hence unlikely to contribute to the cyclic population dynamics of the host. However, the effects on a female's reproductive output might affect the abundance of young susceptible individuals in the population and hence influence the transmission and persistence of the pathogen. Although experimental and long-term capture-mark-recapture studies are required to further clarify the fitness effects of hantavirus infection and their consequences for pathogen dynamics, this study shows that the infection may have complex effects that are dependent on the age of the individual and the time of the breeding season. [ABSTRACT FROM AUTHOR]

Small rodents are key species in many ecosystems. In boreal and subarctic environments, their importance is heightened by pronounced multiannual population cycles. Alarmingly, the previously regular rodent cycles appear to be collapsing simultaneously in many areas. Climate change, particularly decreasing snow quality or quantity in winter, is hypothesized as a causal factor, but the evidence is contradictory. Reliable analysis of population dynamics and the influence of climate thereon necessitate spatially and temporally extensive data. We combined data on vole abundances and climate, collected at 33 locations throughout Finland from 1970 to 2011, to test the hypothesis that warming winters are causing a disappearance of multiannual vole cycles. We predicted that vole population dynamics exhibit geographic and temporal variation associated with variation in climate; reduced cyclicity should be observed when and where winter weather has become milder. We found that the temporal patterns in cyclicity varied between climatically different regions: a transient reduction in cycle amplitude in the coldest region, low-amplitude cycles or irregular dynamics in the climatically intermediate regions, and strengthening cyclicity in the warmest region. Our results did not support the hypothesis that mild winters are uniformly leading to irregular dynamics in boreal vole populations. Long and cold winters were neither a prerequisite for high-amplitude multiannual cycles, nor were mild winters with reduced snow cover associated with reduced winter growth rates. Population dynamics correlated more strongly with growing season than with winter conditions. Cyclicity was weakened by increasing growing season temperatures in the cold, but strengthened in the warm regions. High-amplitude multiannual vole cycles emerge in two climatic regimes: a winter-driven cycle in cold, and a summer-driven cycle in warm climates. Finally, we show that geographic climatic gradients alone may not reliably predict biological responses to climate change. [ABSTRACT FROM AUTHOR]

1. The effects of environment experienced during early development on phenotype as an adult has started to gain vast amounts of interest in various taxa. Some evidence on long-term effects of juvenile environment is available, but replicated experimental studies in wild animals are still lacking. 2. Here we report the first replicated experiment in wild mammals which examines the long-term effects of juvenile and adult environments on individual fitness (reproduction, survival and health). The early development of bank vole ( Myodes glareolus) individuals took place in either food-supplemented or un-supplemented outdoor enclosures. After the summer, adult individuals were reciprocally changed to either a similar or opposite resource environment to overwinter. 3. Adult environment had an overriding effect on reproductive success of females so that females overwintering in food-supplemented enclosures had a higher probability of breeding and advanced the initiation of breeding. However, the characteristics of their litters were determined by juvenile environment: females initially grown in food-supplemented conditions subsequently produced larger litters with bigger pups and a male-biased sex ratio. 4. In males, individuals growing in un-supplemented conditions had the highest survival irrespective of adult environment during winter, whereas in females, neither the juvenile nor adult environments affected their survival significantly. The physiological condition of voles in spring, as determined by haematological parameters, was also differentially affected by juvenile (plasma proteins and male testosterone) and adult (haematocrit) environments. 5. Our results suggest that (i) life-history trajectories of voles are not strictly specialized to a certain environment and (ii) the plastic life-history responses to present conditions can actually be caused by delayed effects of the juvenile environment. More generally, the results are important for understanding the mechanisms of delayed life-history effects as well as recognizing their population dynamic consequences. [ABSTRACT FROM AUTHOR]

Summary 1. The persistence of multiple mating remains one of the fundamental questions in evolutionary biology. In theory, multiple mating is predicted to improve female fitness cumulatively through direct and/or genetic benefits. However, intra-locus sexual conflicts may potentially constrain or even eliminate these benefits owing to the gender load imposed by sexually antagonistic selection. 2. Here, we tested whether sexually antagonistic selection can maintain the variance in multiple mating behaviour of bank voles ( Myodes glareolus) by manipulating the hormone testosterone through artificial selection in the laboratory. Among mammals, testosterone is a sexually dimorphic fitness-related trait under selection and is known to affect mating behaviour. We conducted mating trials in which females derived from family-based selection of testosterone were sequentially paired with four males of different testosterone profiles. 3. We show that artificial selection for high testosterone increased the mating rate of males, but clearly decreased the number of partners that females mated with (and vice versa). Because multiple mating was beneficial for the reproductive success of both sexes, as evidenced by the positive Bateman gradients, the divergent evolutionary interests of testosterone between the sexes can maintain this polygynandrous mating system. 4. Our results highlight how mating rate is concordantly selected in both sexes; however, it is largely influenced by testosterone, which is under sexually antagonistic selection. 5. This study is the first one to emphasise the direct and indirect effects of the endocrine system not only on reproductive physiology and behaviour but also for the evolution of genetic mating strategies in mammals. [ABSTRACT FROM AUTHOR]

1. Optimal parental sex allocation depends on the balance between the costs of investing into sons vs. daughters and the benefits calculated as fitness returns. The outcome of this equation varies with the life history of the species, as well as the state of the individual and the quality of the environment. 2. We studied maternal allocation and subsequent fecundity costs of bank voles, Myodes glareolus, by manipulating both the postnatal sex ratio (all-male/all-female litters) and the quality of rearing environment (through manipulation of litter size by −2/+2 pups) of their offspring in a laboratory setting. 3. We found that mothers clearly biased their allocation to female rather than male offspring regardless of their own body condition. Male pups had a significantly lower growth rate than female pups, so that at weaning, males from enlarged litters were the smallest. Mothers produced more milk for female litters and also defended them more intensively than male offspring. 4. The results agree with the predictions based on the bank vole life history: there will be selection for greater investment in daughters rather than sons, as a larger size seems to be more influencial for female reproductive success in this species. Our finding could be a general rule in highly polygynous, but weakly dimorphic small mammals where females are territorial. 5. The results disagree with the narrow sense Trivers & Willard hypothesis, which states that in polygynous mammals that show higher variation in male than in female reproductive success, high-quality mothers are expected to invest more in sons than in daughters. [ABSTRACT FROM AUTHOR]

The influence of pathogens on host fitness is one of the key questions in infection ecology. Hantaviruses have coevolved with their hosts and are generally thought to have little or no effect on host survival or reproduction. We examined the effect of Puumala virus (PUUV) infection on the winter survival of bank voles (Myodes glareolus), the host of this virus. The data were collected by monitoring 22 islands over three consecutive winters (a total of 55 island populations) in an endemic area of central Finland. We show that PUUV infected bank voles had a significantly lower overwinter survival probability than antibody negative bank voles. Antibody negative female bank voles from low-density populations living on large islands had the highest survival. The results were similar at the population level as the spring population size and density were negatively correlated with PUUV prevalence in the autumn. Our results provide the first evidence for a significant effect of PUUV on host survival suggesting that hantaviruses, and endemic pathogens in general, deserve even more attention in studies of host population dynamics. [ABSTRACT FROM AUTHOR]

Lack of food resources has been suggested as a factor which limits the growth of cyclic vole populations. During peak phases of the cycle, vole population growth typically ceases during late autumn or early winter, and is followed by a decrease in density over the winter. To investigate whether this decrease is due to increased mortality induced by a depletion of food resources, we studied overwinter food consumption and physiological condition of field voles ( Microtus agrestis) in western Finland in both an increase and a decrease phase of a three-year population cycle. The growth rate of vole populations was negatively related both to prevailing vole densities and to densities six months earlier. The condition index of voles, as well as their blood levels of haematocrit, proteins, free fatty acids and immunoglobulin G, were positively related to population growth rate when populations were declining. When populations were increasing, these parameters tended to be negatively related to population growth rate. The overall physiological condition of voles was lower in the winter of the decrease phase as compared to the increase phase. The return rate of voles, a proxy of survival, was also lower in the decrease than in the increase phase of the cycle and positively related to haematocrit levels. Almost 90% of all green vegetation shoots were consumed by voles during the winter of the decrease phase while only two thirds were eaten in the increase phase. Our results suggest that the winter decrease phase of cyclic vole populations is associated with both a deterioration in the physiological condition of voles and a significant depletion of winter food resources. This implies that malnutrition induces poor physiological condition in voles, which in turn may increase mortality either directly through starvation or indirectly through increased susceptibility to predators and pathogens. [ABSTRACT FROM AUTHOR]

Summary 1. Allocation of reproductive effort between the number and size of offspring determines the immediate rearing environment for the growing young. As the number of offspring increases, the amount of parental investment per individual offspring decreases, and the quality of the rearing environment is expected to decrease. This may result in a lower quality of offspring reared in such conditions. 2. We studied the effects of the rearing environment on the quality of juvenile bank voles, Clethrionomys glareolus , with different initial body sizes at birth in a 2 × 2 factorial experiment. The rearing environment was manipulated by enlarging both the litter size by two extra pups, and mean offspring body size at birth by replacing the original litter with heavier pups from smaller litters. Offspring quality was estimated from body size measurements, parasitic infection with Eimeria spp. and the level of immune response to a novel antigen. 3 The analyses revealed that large body size at birth was an advantage in ‘normal’ rearing environments, but a disadvantage in poor ones. The initially normal sized offspring grown in enlarged litters had a relatively good capacity for growth and high immune function confirming that a poor rearing environment alone does not reduce their quality. 4 Our findings that the benefits of large body size depend on the rearing environment suggest that offspring body size is adjusted in relation to litter size, and thus the evolution of these two traits is combined. [ABSTRACT FROM AUTHOR]

For three years, we manipulated litter size by adding or subtracting pups in eight wild populations of the bank vole, Clethrionomys glareolus, to examine reproductive costs and allocation of reproductive effort between offspring number and size. In general, litter enlargements did not increase the number of weanlings per mother and significantly decreased the size of weanlings. Reproductive effort and the breeding success of individuals varied within breeding seasons, but time of breeding and litter manipulation did not interact to affect reproductive trade-offs. Our 3-yr field experiment revealed that litter enlargements also reduced survival and fecundity of mothers. Small mammals have been considered typical income breeders, in which potential reproductive costs may be masked due to their ability to compensate for increased energetic demands of reproduction. Our results provide evidence that, in the wild, females may be incapable of escaping the costs of reproduction. [ABSTRACT FROM AUTHOR]

1. Reproductive success of individual females may be determined by density-dependent effects, especially in species where territory provides the resources for a reproducing female and territory size is inversely density-dependent. 2. We manipulated simultaneously the reproductive effort (litter size manipulation: ± 0 and + 2 pups) and breeding density (low and high) of nursing female bank voles Clethrionomys glareolus in outdoor enclosures. We studied whether the reproductive success (number and quality of offspring) of individual females is density-dependent, and whether females can compensate for increased reproductive effort when not limited by saturated breeding density. 3. The females nursing their young in the low density weaned significantly more offspring than females in the high density, independent of litter manipulation. 4. Litter enlargements did not increase the number of weanlings per female, but offspring from enlarged litters had lower weight than control litters. 5. In the reduced density females increased the size of their home range, but litter manipulation had no significant effect on spacing behaviour of females. Increased home range size did not result in heavier weanlings. 6. Mother’s failure to successfully wean any offspring was more common in the high density treatment, whereas litter manipulation or mother’s weight did not affect weaning success. 7. We conclude that reproductive success of bank vole females is negatively density-dependent in terms of number, but not in the quality of weanlings. 8. The nursing effort of females (i.e. the ability to provide enough food for pups) seems not to be limited by density-dependent factors. [ABSTRACT FROM AUTHOR]

Many prey animals have life-history strategies that seem to have evolved to avoid predation from specialist predators. During the past few years, the hypothesis of breeding suppression (BSH) of voles as an adaptation to avoid small mustelid predation has prompted several empirical and theoretical studies. However, the validity of empirical work as well as justification of the conclusions in these studies have been criticized. Here we report results of an experiment in which we studied the breeding suppression of bank voles, Clethrionomys glareolus, in four replicated enclosures. We found no effects of simulated least weasel, Mustela nivalis nivalis, predation risk on the reproductive output of female voles. In contrast to earlier laboratory studies, the weights of females did not differ between treatment groups after the experiment. We reanalyzed results of our earlier laboratory studies in light of these results and criticism of the BSH. At present there is no direct evidence for breeding suppression of voles in fieldpopulations. Furthermore, the underlying assumptions of the BSH havenot been tested experimentally. Thus the most parsimonious explanation for breeding suppression is that it may be a methodological or laboratory artifact. [ABSTRACT FROM AUTHOR]