Yolk corticosterone data

Includes data on tritiated steroids found in the three egg components over the course of egg development as well as TLC data in two different solvent systems

Comparison of <i>a priori</i> candidate models of individual differences in corticosterone responsiveness.

<p>The variables under the column “Random effect” indicate the specific random effect in the model in which “band” corresponds to the individual. K is the number of parameters in the model, DIC is deviance information criterion, ΔDIC indicates the difference between DIC value of a given model and the model with the lowest DIC. All models were fit with treatment as a fixed effect in the model; therefore, models differ in their random structure.</p><p>Comparison of <i>a priori</i> candidate models of individual differences in corticosterone responsiveness.</p

Relationship between the weekly changes in body mass and corticosterone levels in individual house sparrows.

<p>Individuals are denoted by their band number above each box. Panels are ordered in function of the individuals' conditional responsiveness (i.e., the slope of the fitted line), from left to right starting with the top row.</p

Mean ± SE (a) body mass (b) corticosterone levels during the experiment.

<p>Birds received either a food restricted ('FR') or a control diet, which corresponded to 60% or 110% of their daily food consumption, respectively. During the third week of the experiment, all birds received <i>ad libitum</i> food for one week ('recov'). Birds were randomly allocated into two groups that differed only in the order of the treatments. Black dots and solid lines represent birds starting with the control diet (treatments indicated above the lines), blue triangles and dotted lines represent birds starting with the food restricted diet (treatments indicated below the lines). Note that blood samples were not collected after the recovery period (after week 3), but body mass was recorded.</p

Relationship between the weekly changes in body mass and corticosterone levels in all experimental house sparrows.

<p>Note that individuals are represented with multiple points. The line represents the model fit of the fixed model that accounts for the repeated nature of the data.</p

The concept of reaction norms.

<p>Reaction norms are the phenotypic expression of a single genotype across a range of environments. Reaction norms can be characterized by the intercept (e.g. initial hormone levels) and the slope of the line (e.g. stress responsiveness). Panel (A) depicts a hypothetical scenario, where there is only one reaction norm in the population (e.g. due to the lack of genetic variance or due to a strong selection for an optimal reaction norm). In this scenario, selection cannot act on hormone levels, because there is no variance between genotypes (individuals A and B have the same slope and intercept), i.e., all individuals will have identical hormone levels under the same environmental circumstances. However, without knowing the reaction norm, differences between the individuals (denoted by A and B) may be mistakenly attributed to results of natural selection on the hormone levels (if fitness is higher in the good environment than in the poor one). In panel (B), individuals differ in their reaction norms (both in the intercept and the slope). Different individuals (C and D) are sampled twice, once in a good environmental condition and once in a bad environmental condition. In this case, the between- and within-individual variation in hormone levels can be separated, and the reaction norm can be defined. If fitness related traits are also measured, then we can ask whether selection acts on the different reaction norms. In this special case, the reaction norms cross, making an individual by environment (I×E) interaction that has further consequences on how natural selection can act on the reaction norms in such a situation. See the text and references therein for further details.</p