Physiological consequences of acculturation: a 20-year study of fitness in an Inuit community

Surveys in 1969/1970, 1979/1980, and 1989/ 1990 assessed physical fitness among adult Inuit living in Igloolik, Northwest Territories, Canada, during a period of rapid acculturation to a sedentary lifestyle. MANOVA for age, cohort, and age-cohort effects indicated significant trends to greater skinfold readings [male (M) and female (F)] and body mass (F only), a lower handgrip and knee extension force (M and F), and lower step test predictions of aerobic power (M and F) in the more recent cohorts, with no change of forced vital capacity, 1-s forced expiratory volume, or hemoglobin level. By 1989/1990, continuing hunters tended to have thicker skinfolds than other villagers, and showed no advantage of aerobic power. The average fitness of the sample when tested in 1989/1990 was comparable with that of sedentary populations in Southern Canada, but a minority of villagers who now practiced regular sport had conserved the high levels of fitness that were observed in 1969/1970. We conclude that the fitness of this community appears to have deteriorated markedly as it has become more sedentary, and we thus recommend that health authorities develop methods of promoting an active lifestyle that are culturally appropriate to the populations of circumpolar settlements.     

Physiological indicators of fitness in benthic invertebrates: a useful measure for ecological health assessment and experimental ecology

Physiological indicators of fitness present a measure of an organism’s response to a changing environment. An analysis of how these organisms allocate and store their energy resources provides an understanding of how they cope with such environmental changes. Each individual has to balance the investment necessary to acquire a certain resource with the energy gained by it. This trade-off can be monitored by measuring several physiological indicators of fitness such as energy storage components, metabolic state or RNA/DNA ratio. Because environmental adaptations and ecological strategies of survival are best examined within the natural environment, our research has to rely on the physiological indicators that are easily accessible in the field. The physiological indicators presented here are significant for an individual’s fitness and in turn lead to reliable values in field-collected samples. Based on our own expertise and on a literature survey, the physiological relevance of the presented indicators is explained. Furthermore, some consideration to the analytical methods used to obtain the physiological indicators is given, and possible errors introduced at the sampling site and during the laboratory procedures are discussed. This work demonstrates that the integration of ecological and physiological expertise facilitates the identification of future ecological problems much earlier than separate approaches of both disciplines alone.     

Joint inference of the distribution of fitness effects of deleterious mutations and population demography based on nucleotide polymorphism frequencies

The distribution of fitness effects of new mutations (DFE) is important for addressing several questions in genetics, including the nature of quantitative variation and the evolutionary fate of small populations. Properties of the DFE can be inferred by comparing the distributions of the frequencies of segregating nucleotide polymorphisms at selected and neutral sites in a population sample, but demographic changes alter the spectrum of allele frequencies at both neutral and selected sites, so can bias estimates of the DFE if not accounted for. We have developed a maximum-likelihood approach, based on the expected allele-frequency distribution generated by transition matrix methods, to estimate parameters of the DFE while simultaneously estimating parameters of a demographic model that allows a population size change at some time in the past. We tested the method using simulations and found that it accurately recovers simulated parameter values, even if the simulated demography differs substantially from that assumed in our analysis. We use our method to estimate parameters of the DFE for amino acid-changing mutations in humans and Drosophila melanogaster. For a model of unconditionally deleterious mutations, with effects sampled from a gamma distribution, the mean estimate for the distribution shape parameter is approximately 0.2 for human populations, which implies that the DFE is strongly leptokurtic. For Drosophila populations, we estimate that the shape parameter is approximately 0.35. Differences in the shape of the distribution and the mean selection coefficient between humans and Drosophila result in significantly more strongly deleterious mutations in Drosophila than in humans, and, conversely, nearly neutral mutations are significantly less frequent.     

Physiological and visual refuges in a metalimnion: an experimental study of effects of clay turbidity and an oxygen minimum on fish predation

1. The effectivity of elevated clay turbidity and low-oxygen concentration in the metalimnion as refuges for chaoborid larvae against fish predation was studied in experimental water columns.
2. When 70–80 nephelometric turbidity unit clay turbidity was combined with 3–4 mg L⁻¹ oxygen concentration, prey capture rate by fish (golden orfe Leuciscus idus ) was reduced by 74% compared with the control treatment with no refuges. Oxygen and turbidity refuges alone did not significantly reduce the feeding rate.
3. All fish in the control treatment dwelled in the metalimnion, but 36% of the fish in the low-oxygen treatment and 23% of the fish in the turbidity treatment stayed in the epilimnion. In the combined treatment, 54% of the fish were in the epilimnion.
4. The results demonstrated that a combination of moderately elevated turbidity and lowered oxygen concentration in the metalimnion is an effective protection against fish predation, while turbidity or oxygen refuge alone are much less effective.
5. In the treatment with the combined refuge, oxygen concentration limited the time fish could spend in the metalimnion and turbidity affected the detection of prey through changes in reactive distance.
6. Because of the combined effects of turbidity and oxygen refuges, planktivorous fish and phantom midge larvae may co-occur in clay-turbid lakes in high densities. Such situation is problematic for biomanipulation, which aims to enhance the grazing rate of zooplankton through reduction of planktivorous fish.     

The effects of phenological mismatches on demography

Climate change is altering the phenology of species across the world, but what are the consequences of these phenological changes for the demography and population dynamics of species? Time-sensitive relationships, such as migration, breeding and predation, may be disrupted or altered, which may in turn alter the rates of reproduction and survival, leading some populations to decline and others to increase in abundance. However, finding evidence for disrupted relationships, or lack thereof, and their demographic effects, is difficult because the necessary detailed observational data are rare. Moreover, we do not know how sensitive species will generally be to phenological mismatches when they occur. Existing long-term studies provide preliminary data for analysing the phenology and demography of species in several locations. In many instances, though, observational protocols may need to be optimized to characterize timing-based multi-trophic interactions. As a basis for future research, we outline some of the key questions and approaches to improving our understanding of the relationships among phenology, demography and climate in a multi-trophic context. There are many challenges associated with this line of research, not the least of which is the need for detailed, long-term data on many organisms in a single system. However, we identify key questions that can be addressed with data that already exist and propose approaches that could guide future research.     

Physiological,but not fitness,effects of two interacting haemoparasitic infections in a wild rodent

In contrast to the conditions in most laboratory studies, wild animals are routinely challenged by multiple infections simultaneously, and these infections can interact in complex ways. This means that the impact of a parasite on its host’s physiology and fitness cannot be fully assessed in isolation, and requires consideration of the interactions with other co-infections. Here we examine the impact of two common blood parasites in the field vole (Microtus agrestis): Babesia microti and Bartonella spp., both of which have zoonotic potential. We collected longitudinal and cross-sectional data from four populations of individually tagged wild field voles. This included data on biometrics, life history, ectoparasite counts, presence/absence of microparasites, immune markers and, for a subset of voles, more detailed physiological and immunological measurements. This allowed us to monitor infections over time and to estimate components of survival and fecundity. We confirm, as reported previously, that B. microti has a preventative effect on infection with Bartonella spp., but that the reverse is not true. We observed gross splenomegaly following B. microti infection, and an increase in IL-10 production together with some weight loss following Bartonella spp. infection. However, these animals appeared otherwise healthy and we detected no impact of infection on survival or fecundity due to the two haemoparasite taxa. This is particularly remarkable in the case of B. microti which induces apparently drastic long-term changes to spleen sizes, but without major adverse effects. Our work sheds light on the ecologies of these important zoonotic agents, and more generally on the influence that interactions among multiple parasites have on their hosts in the wild.     

Contrasting cascade effects of carnivores on plant fitness: a meta-analysis

1. Although carnivores indirectly improve plant fitness by decreasing herbivory, they may also decrease plant reproduction by disrupting plant-pollinator mutualism. The overall magnitude of the resulting net effect of carnivores on plant fitness and the factors responsible for the variations in strength and direction of this effect have not been explored quantitatively to date. 2. We performed a meta-analysis of 67 studies containing 163 estimates of the effects of carnivores on plant fitness and examined the relative importance of several potential sources of variation in carnivore effects. 3. Carnivores significantly increased plant fitness via suppression of herbivores and decreased fitness by consuming pollinators. The overall net effect of carnivores on plant fitness was positive (32% increase), indicating that effects via herbivores were stronger than effects via pollinators. 4. Parasitoids had stronger positive effect on plant fitness than predators. Active hunters increased plant fitness, whereas stationary predators had no significant effect, presumably because they were more prone to disrupt plant-pollinator mutualism. Carnivores with broader habitat domain had negative effects on plant fitness, whereas those with narrow habitat domain had positive effects. 5. Predator effects were positive for plants which offered rewards (e.g. extrafloral nectaries) and negative for plants which lacked any attractors. 6. This study adds new knowledge on the factors that determine the strength of terrestrial trophic cascades and highlights the importance of considering simultaneous contrasting interactions in the same study system.     

Physiological testing of basketball players: toward a standard evaluation of anaerobic fitness

The aim of this study was to examine whether the changes in the rules of the game instituted in 2000 have modified the physiological factors of success in basketball. The performances of 8 elite male players and 8 average-level players were compared in order to identify which components of fitness among agility, speed, anaerobic power, anaerobic capacity, and upper body strength were key determinants of performance in modern basketball. Each subject performed 7 tests, including vertical jump (VJ), 20-m sprint, agility T test, suicide sprint, 30-second Wingate anaerobic test (WAnT), isokinetic testing of the knee extensors, and 1 repetition maximum (1RM) bench press test. The statistical difference in the anaerobic performances was assessed by Student's t test. The main results showed that, compared to average-level players, elite-level players achieved significantly better performances in the agility T test (+6.2%), VJ test (+8.8%), peak torques developed by knee extensors (+20.2%), and 1RM bench press (+18.6%, p < 0.05). In contrast, no significant difference between groups was observed on 20-m sprint, suicide run, and parameters of the WAnT (p > 0.05). These results emphasized the importance of anaerobic power in modern basketball, whereas anaerobic capacity does not seem to be a key aspect to consider. In this context, coaches are advised to avoid using exercises lasting >/=30 seconds in their physical fitness programs, but instead to focus on short and intense tests such as VJ, agility T test, and sprints over very short distances (5 or 10 m).     

A silver spoon for a golden future: long-term effects of natal origin on fitness prospects of oystercatchers (Haematopus ostralegus)

1. Long-term effects of conditions during early development on fitness are important for life history evolution and population ecology. Using multistrata mark-recapture models on 20 years of data, we quantified the relation between rearing conditions and lifetime fitness in a long-lived shorebird, the oystercatcher (Haematopus ostralegus). We addressed specifically the relative contribution of short- and long-term effects of rearing conditions to overall fitness consequences. 2. Rearing conditions were defined by differences in natal habitat quality, in which there is a clear dichotomy in our study population. In the first year of life, fledglings from high-quality natal origin had a 1.3 times higher juvenile survival. Later in life (age 3-11), individuals of high-quality natal origin had a 1.6 times higher adult prebreeder survival. The most striking effect of natal habitat quality was that birds that were reared on high-quality territories had a higher probability of settling in high-quality habitat (44% vs. 6%). Lifetime reproductive success of individuals born in high-quality habitat was 2.2 times higher than that of individuals born in low-quality habitat. This difference increased further when fitness was calculated over several generations, due to a correlation between the quality of rearing conditions of parents and their offspring. 3. Long-term effects of early conditions contributed more to overall fitness differences as short-term consequences, contrary to common conceptions on this issue. 4. This study illustrates that investigating only short-term effects of early conditions can lead to the large underestimation of fitness consequences. We discuss how long-term consequences of early conditions may affect settlement decisions and source-sink population interactions.     

Population demography and heterozygosity–fitness correlations in natural guppy populations: An examination using sexually selected fitness traits

Heterozygosity–fitness correlations (HFCs) have been examined in a wide diversity of contexts, and the results are often used to infer the role of inbreeding in natural populations. Although population demography, reflected in population‐level genetic parameters such as allelic diversity or identity disequilibrium, is expected to play a role in the emergence and detectability of HFCs, direct comparisons of variation in HFCs across many populations of the same species, with different genetic histories, are rare. Here, we examined the relationship between individual microsatellite heterozygosity and a range of sexually selected traits in 660 male guppies from 22 natural populations in Trinidad. Similar to previous studies, observed HFCs were weak overall. However, variation in HFCs among populations was high for some traits (although these variances were not statistically different from zero). Population‐level genetic parameters, specifically genetic diversity levels (number of alleles, observed/expected heterozygosity) and measures of identity disequilibrium (g2 and heterozygosity–heterozygosity correlations), were not associated with variation in population‐level HFCs. This latter result indicates that these metrics do not necessarily provide a reliable predictor of HFC effect sizes across populations. Importantly, diversity and identity disequilibrium statistics were not correlated, providing empirical evidence that these metrics capture different essential characteristics of populations. A complex genetic architecture likely underpins multiple fitness traits, including those associated with male fitness, which may have reduced our ability to detect HFCs in guppy populations. Further advances in this field would benefit from additional research to determine the demographic contexts in which HFCs are most likely to occur.     

Sexual selection: the importance of long-term fitness measures

New results from a 20-year study of free-living song sparrows confirm that attractive males contribute more offspring than less attractive males. They also reveal that the offspring of preferred males produce more descendents themselves. Females prefer males with a large song repertoire, which further work shows is a condition-dependent indicator of male quality.     

Inferring the distribution of fitness effects in patient-sampled and experimental virus populations: two case studies

We here propose an analysis pipeline for inferring the distribution of fitness effects (DFE) from either patient-sampled or experimentally-evolved viral populations, that explicitly accounts for non-Wright-Fisher and non-equilibrium population dynamics inherent to pathogens. We examine the performance of this approach via extensive power and performance analyses, and highlight two illustrative applications - one from an experimentally-passaged RNA virus, and the other from a clinically-sampled DNA virus. Finally, we discuss how such DFE inference may shed light on major research questions in virus evolution, ranging from a quantification of the population genetic processes governing genome size, to the role of Hill-Robertson interference in dictating adaptive outcomes, to the potential design of novel therapeutic approaches to eradicate within-patient viral populations via induced mutational meltdown.Subject terms: Population genetics, Evolutionary genetics     

Physiological responses to fitness activities: a comparison between land-based and water aerobics exercise

This study compared the heart rate (HR) and blood lactate (BL) responses in young healthy women performing the same routine of aerobics exercise in 3 different conditions: on land, in shallow water (0.8 m), and in deep water (1.4 m). The average age and body mass index (BMI) of the group were 27.4 years and 22.6 kg.m(-2), respectively. The highest HR and BL values were reached during land aerobics (median HR values were 138.0 and 161.5 b.min(-1), and lactate values were 3.10 and 5.65 mmol.L(-1) at slow and at faster pace, respectively). These parameters were progressively reduced going from shallow water (121.5 and 154.0 b.min(-1), 1.75 and 3.15 mmol.L(-1)) to deep water (97.5 and 113.5 b.min(-1), 1.70 and 1.75 mmol.L(-1)). The HR measured as percentage of maximum HR varied from 48.43% to 77.53% depending on the water depth and the pace. These data indicate that exercise in water significantly reduces HR and BL production compared with the same exercise performed on land.     

Grazing and UV radiation effects on an Antarctic intertidal microalgal assemblage: a long-term field study

A 15 week field experiment (austral summer Nov–Mar) was carried out in an intertidal hard bottom platform in Antarctica (King George Island). To test whether grazing and ultraviolet radiation (UVR) influenced the succession of a benthic microalgal assemblage, a two-factorial design was used (1) ambient radiation, >280 nm; (2) ambient minus UV-B, >320 nm; (3) ambient minus UVR, >400 nm versus grazer–no grazer). On four sampling occasions microalgae were identified, counted and carbon contents were calculated. The assemblage was dominated by the diatom genera Navicula and Cocconeis. Biomass was generally low in all treatments but was significantly reduced by grazing throughout the experiment. No significant UV effects were found. Grazer absence particularly favoured diatoms of the genus Cocconeis. We conclude that the Antarctic microalgal assemblage was unaffected by present day UVR whereas grazers acted as important drivers on the intertidal microalgal community structure.     

The effects of wheat-pea mixed intercropping on biocontrol potential of generalist predators in a long-term experimental trial

Arthropod generalist predators can be effective natural control agents of pests and weeds in agroecosystems. Their activity and contribution to biocontrol may increase in response to more complex agricultural habitats. In this study, we investigated the effects of winter wheat-pea mixed intercropping on the biocontrol potential of generalist predators compared with the respective mono-crops. We evaluated not only the effects during the intercropping season but also the pre-crop values of the mixture for the subsequent barley crop. Furthermore, we evaluated the influence of different long-term soil organic carbon and fertility management regimes on activity and biocontrol potential of predators. Field work was conducted over two seasons in a field experiment located in Gembloux, Belgium. A set of proxies for ecosystem functions were measured using the Rapid Ecosystem Function Assessment approach. We measured attack and predation rates of sentinel prey and weed seeds artificially placed in the field. Furthermore, we assessed activity density of the main groups of generalist predators during the exposure of the baits. Our results showed that crop type affected activity and biocontrol potential of predators. Predation rates were much lower in wheat than pea and wheat-pea. The mixture wheat-pea had a positive effect on predator activity density compared to wheat mono-crop, while pea supported an intermediate activity of epigeal predators. In the second season of the field work, we found the highest biocontrol potential by predators in barley plots cultivated after pea. Finally, our results failed to find any differences in biocontrol potential of predators between long-term soil organic carbon and fertilisation management strategies. These results suggest that crop type has a major relevance in influencing the activity of generalist predators, and the mixed intercropping wheat-pea may represent a valid strategy to enhance biological pest control in comparison to wheat cultivated as mono-crop. Furthermore, we show that the cultivation of pea as mono-crop may have an important pre-crop value within the rotation increasing the provision of ecosystem services such as biocontrol.     

Linkages among life-history components through time: Carryover effects on the demography of a short-lived polycarpic plant

? Premise of the study: Current reproduction in polycarpic plants may be affected by a wide variety of factors, including carryover or "historical" effects derived from environments experienced early in life and from previous investments in organ preformation or other life functions, such as growth or reproduction. Historical effects as determinants of plant reproductive success in a specific season have received considerably less attention than events during the current reproductive episode, especially for short-lived plants. ? Methods: We used structural equation modeling to assess direct and indirect relations between past reproduction and both subsequent reproduction and growth in Helianthemum squamatum, a short-lived polycarpic plant. Additionally, we explored the effects of current reproduction on future survival (binomial variable) by using logistic regression. ? Key results: Historical effects derived from previous growth positively affected current reproduction, suggesting the existence of a reproductive hierarchy in the population, in which some individuals are consistently better growers and seeders. The lack of effects of current reproduction on future reproduction, together with the existence of a negative effect on future survival, suggests that to invest maximally in reproduction at the expense of a short life span may be the optimal strategy for H. squamatum, a species inhabiting very unpredictable ecosystems. ? Conclusions: Historical effects derived from past investments in growth or reproduction may have important consequences for current plant performance and may play an essential role in shaping life histories.