J. Ornithol 12/2007; 148:633-642. DOI: 10.1007/s10336-007-0191-8
Good estimates of the genetic parameters of natural populations, such as heritability, are essential for both understanding
how genetic variation is maintained and estimating a population’s evolutionary potential. Long-term studies on birds are especially
amenable for calculating such estimates because of the ease with which pedigrees can be inferred. Recent ‘animal model’ methodology,
originally developed by animal breeders to identify animals of high genetic merit, has been applied to natural bird populations
of known pedigree. Animal models are more powerful than traditional analyses such as parent–offspring regression because they
use all of the available pedigree information simultaneously. In doing so, they can accommodate common phenomena like selection
and inbreeding and are especially suitable for the complex and incomplete pedigrees typical of natural populations. Animal
models not only provide a better way of estimating genetic and environmental variance components, they also allow individual
phenotypes to be separated into their genetic and environmental components. Here we aim to provide the interested ornithologist
with an accessible entry into the vast and sometimes daunting quantitative genetics literature and, in particular, into the
literature on the animal model. We outline not only the possibilities offered by the animal model for the accurate estimation
of genetic parameters in the wild but also associated potential pitfalls and limitations. On the whole, we aim to provide
an accessible and up-to-date overview of the rapidly developing and exciting field of evolutionary genetics applied to long-term
studies of wild bird populations.
"The reason for using this approach is that, due to technical constraints, a single line of insects was studied on each diet type so that any differences among individuals in the two different parental diets could exclusively be due to genetic drift. By adding an “animal” random effect in the models this can be accounted for , . Animal models were fitted with Bayesian Markov chain Monte Carlo (MCMC) techniques implemented in the MCMCglmm package . "
[Show abstract][Hide abstract] ABSTRACT: Food shortage is a common situation in nature but little is known about the strategies animals use to overcome it. This lack of knowledge is especially true for outbreaking insects, which commonly experience nutritional stress for several successive generations when they reach high population densities. The aim of this study is to evaluate the life history consequences of chronic nutritional stress in the outbreaking moth Choristoneura fumiferana. Larvae were reared on two different artificial diets that emulate nutritional conditions larvae face during their natural population density cycle (low and medium quality artificial diets). After four generations, a subset of larvae was fed on the same diet as their parents, and another on the opposite diet. We explored larval life-history strategies to cope with nutritional stress, its associated costs and the influence of nutritional conditions experienced in the parental generation. We found no evidence of nutritional stress in the parental generation increasing offspring ability to feed on low quality diet, but the contrary: compared to offspring from parents that were fed a medium quality diet, larvae from parents fed a low quality diet had increased mortality, reduced growth rate and reduced female reproductive output. Our results support a simple stress hypothesis because the negative effects of malnutrition accumulated over successive generations. Density-dependent deterioration in plant quality is thought to be an important factor governing the population dynamics of outbreaking insects and we hypothesize that chronic nutritional stress can be a driver of outbreak declines of C. fumiferana, and of forest insects in general.
PLoS ONE 02/2014; 9(2):e88039. DOI:10.1371/journal.pone.0088039 · 3.23 Impact Factor
"As birds can be easily individually marked by metal and coloured plastic leg-rings, and many avian species have extended brood care, in which often both parents take part, the necessary data for quantitative genetic analyses are comparably easily collected in birds. Several long-term studies have collected such data in some cases already for decades and they now offer a wealth of high-quality individual data suitable for sophisticated quantitative genetic analyses (Collins 2001; Postma and Charmantier 2007). "
[Show abstract][Hide abstract] ABSTRACT: There are multiple observations around the globe showing that in many avian species, both the timing of migration and breeding have advanced, due to warmer springs. Here, we review the literature to disentangle the actions of evolutionary changes in response to selection induced by climate change versus changes due to individual plasticity, that is, the capacity of an individual to adjust its phenology to environmental variables. Within the abundant literature on climate change effects on bird phenology, only a small fraction of studies are based on individual data, yet individual data are required to quantify the relative importance of plastic versus evolutionary responses. While plasticity seems common and often adaptive, no study so far has provided direct evidence for an evolutionary response of bird phenology to current climate change. This assessment leads us to notice the alarming lack of tests for microevolutionary changes in bird phenology in response to climate change, in contrast with the abundant claims on this issue. In short, at present we cannot draw reliable conclusions on the processes underlying the observed patterns of advanced phenology in birds. Rapid improvements in techniques for gathering and analysing individual data offer exciting possibilities that should encourage research activity to fill this knowledge gap.
"If immigration and drift can be excluded, a change in breeding values consistent with the expected change based on selection patterns can be interpreted as microevolution. Several caveats surround the use of the animal model (Postma 2006; Postma and Charmantier 2007; Hadfield et al. 2010), notably when accounting for errors in the estimation of breeding values (Hadfield et al. 2010; Wilson et al. 2010). However provided these are properly accounted for (e.g. using MCMCglmm, Hadfield 2010), the animal model remains a useful tool. "
[Show abstract][Hide abstract] ABSTRACT: Climate change is expected to induce many ecological and evolutionary changes. Among these is the hypothesis that climate warming will cause a reduction in body size. This hypothesis stems from Bergmann's rule, a trend whereby species exhibit a smaller body size in warmer climates, and larger body size under colder conditions in endotherms. The mechanisms behind this rule are still debated, and it is not clear whether Bergmann's rule can be extended to predict the effects of climate change through time. We reviewed the primary literature for evidence (i) of a decrease in body size in response to climate warming, (ii) that changing body size is an adaptive response and (iii) that these responses are evolutionary or plastic. We found weak evidence for changes in body size through time as predicted by Bergmann's rule. Only three studies investigated the adaptive nature of these size decreases. Of these, none reported evidence of selection for smaller size or of a genetic basis for the size change, suggesting that size decreases could be due to nonadaptive plasticity in response to changing environmental conditions. More studies are needed before firm conclusions can be drawn about the underlying causes of these changes in body size in response to a warming climate.
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