Perturbations in growth trajectory due to early diet affect age-related deterioration in performance

Fluctuations in early developmental conditions can cause changes in growth trajectories that subsequently affect the adult phenotype. Here, we investigated whether compensatory growth has long-term consequences for patterns of senescence. Using three-spined sticklebacks (Gasterosteus aculeatus), we show that a brief period of dietary manipulation in early life affected skeletal growth rate not only during the manipulation itself, but also during a subsequent compensatory phase when fish caught up in size with controls. However, this growth acceleration influenced swimming endurance and its decline over the course of the breeding season, with a faster decline in fish that had undergone faster growth compensation. Similarly, accelerated growth led to a more pronounced reduction in the breeding period (as indicated by the duration of sexual ornamentation) over the following two breeding seasons, suggesting faster reproductive senescence. Parallel experiments showed a heightened effect of accelerated growth on these age-related declines in performance if the fish were under greater time stress to complete their compensation prior to the breeding season. Compensatory growth led to a reduction in median life span of 12% compared to steadily growing controls. While life span was independent of the eventual adult size attained, it was negatively correlated with the age-related decline in swimming endurance and sexual ornamentation. These results, complementary to those found when growth trajectories were altered by temperature rather than dietary manipulations, show that the costs of accelerated growth can last well beyond the time over which growth rates differ and are affected by the time available until an approaching life-history event such as reproduction

Niche variation and the maintenance of variation in body size in a burying beetle

© 2015 The Authors. Ecological Entomology published by John Wiley & Sons Ltd on behalf of Royal Entomological Society. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.Online Version of Record published before inclusion in an issue.The final published version is available via DOI: 10.1111/een.122751. In burying beetles (Nicrophorinae) body size is known to provide both a fecundity advantage (in females) and successful resource defence (in males and females). Despite this, considerable variation in body sizes is observed in natural populations. 2. A possible explanation for the maintenance of this variation, even with intra- and interspecific resource competition, is that individuals might assort according to body size on different sized breeding-resources. 3. We tested the prediction that ‘bigger is always better’ in the wild, and in the laboratory, by experimentally manipulating combinations of available breeding-resource size (mouse carcasses) and competitor’s body size in Nicrophorus vespilloides (Herbst 1783). 4. In the field, large female beetles deserted small carcasses, without breeding, more often than they did larger carcasses, but small females used carcasses indiscriminately with respect to size. In the laboratory large beetles reared larger broods (with more offspring) on larger carcasses than small beetles, but on small carcasses small beetles had a reproductive advantage over large ones. Offspring size covaried with carcass size independently of parental body size. 5. Our combined results suggest breeding resource value depends on an individual’s body size, and variation in body size is environmentally induced: maintained by differences in available carcass sizes. This produces a mechanism by which individual specialisation leads to an increase in niche variation via body size in these beetles.This work was supported by a PhD studentship from the Natural Environment Research Council (NE/1528326/1) and a grant from NERC to N.J.R. and A.J.M. (NE/1025468/1)

Non‐consumptive effects of predation: does perceived risk strengthen the genetic integration of behaviour and morphology in stickleback?

Predators can shape genetic correlations in prey by altering prey perception of risk. We manipulated perceived risk to test whether such non‐consumptive effects tightened behavioural trait correlations in wild‐caught stickleback from high‐ compared to low‐risk environments due to genetic variation in plasticity. We expected tighter genetic correlations within perceived risk treatments than across them, and tighter genetic correlations in high‐risk than in low‐risk treatments. We identified genetic variation in plasticity, with genetic correlations between boldness, sociality, and antipredator morphology, as expected, being tighter within treatments than across them, for both of two populations. By contrast, genetic correlations did not tighten with exposure to risk. Tighter phenotypic correlations in wild stickleback may thus arise because predators induce correlational selection on environmental components of these traits, or because predators tighten residual correlations by causing environmental heterogeneity that is controlled in the laboratory. Our study places phenotypic integration firmly into an ecological context

Oxidative status and fitness components in the Seychelles warbler

1. Oxidative damage, caused by reactive oxygen species during aerobic respiration, is thought to be an important mediator of life-history trade-offs. To mitigate oxidative damage, antioxidant defence mechanisms are deployed, often at the cost of resource allocation to other body functions. Both reduced resource allocation to body functions and direct oxidative damage may decrease individual fitness, through reducing survival and/or reproductive output. 2. The oxidative costs of reproduction have gained much attention recently, but few studies have investigated the long-term consequences of oxidative damage on survival and (future) reproductive output under natural conditions. 3. Using a wild population of the cooperatively breeding Seychelles warbler (Acrocephalus sechellensis), we tested the prediction that high levels of reactive oxygen species, or high antioxidant investments to avoid oxidative damage, have fitness consequences because they reduce survival and/or reproductive output. 4. We found that individuals with higher circulating non-enzymatic antioxidant capacity had a lower probability of surviving until the next year. However, neither current reproductive output, nor future reproductive output in the surviving individuals, was associated with circulating non-enzymatic antioxidant capacity or oxidative damage. 5. The negative relationship between antioxidant capacity and survival that we observed concurs with the findings of an extensive comparative study on birds, however the mechanisms underlying this association remain to be resolved

Can sexual selection drive female life histories? A comparative study on Galliform birds

Sexual selection is an important driver of many of the most spectacular morphological traits that we find in the animal kingdom (for example see Andersson, 1994). As such, sexual selection is most often emphasized as

The ecogenetic link between demography and evolution : can we bridge the gap between theory and data?

Calls to understand the links between ecology and evolution have been common for decades. Population dynamics, i.e. the demographic changes in populations, arise from life history decisions of individuals and thus are a product of selection, and selection, on the contrary, can be modified by such dynamical properties of the population as density and stability. It follows that generating predictions and testing them correctly requires considering this ecogenetic feedback loop whenever traits have demographic consequences, mediated via density dependence (or frequency dependence). This is not an easy challenge, and arguably theory has advanced at a greater pace than empirical research. However, theory would benefit from more interaction between related fields, as is evident in the many near-synonymous names that the ecogenetic loop has attracted. We also list encouraging examples where empiricists have shown feasible ways of addressing the question, ranging from advanced data analysis to experiments and comparative analyses of phylogenetic data