Is there a genetic correlation between movement and immobility in field populations of a beetle?

Genetic correlations among behavioural traits are often controlled by pleiotropic genes. Many studies suggest the existence of genetic correlations among behavioural traits based on artificial selection experiments in the laboratory. However, few studies have examined whether behavioural correlations in the laboratory are maintained in the field, where natural selection works. Artificial selection experiments showed a behavioural correlation among death feigning, walking movement, and locomotor activity in the red flour beetle (Tribolium castaneum). This study investigated whether this behavioural correlation is observed in wild T. castaneum populations. We also collected beetles from various regions in Japan and investigated the geographic variation in these traits. There was geographic variation in the three behavioural traits. However, these behavioural traits were not correlated. The results suggest that the genetic correlations among behavioural traits are not maintained in the field. Therefore, the results derived from laboratory experiments may be overestimated. The same correlation between traits was not believed to arise in the field, as the indoor results may have been caused by unrealistic selection pressures. Further laboratory and field investigations are both needed.

Morphology does not covary with predicted behavioural correlations of the domestication syndrome in dogs

Domesticated animals display suites of altered morphological, behavioural and physiological traits compared to their wild ancestors, a phenomenon known as the domestication syndrome (DS). Because these alterations are observed to co-occur across a wide range of present day domesticates, the traits within the DS are assumed to covary within species and a single developmental mechanism has been hypothesized to cause the observed co-occurrence. However, due to the lack of formal testing it is currently not well-resolved if the traits within DS actually covary. Here we test the hypothesis that the presence of the classic morphological domestication traits white pigmentation, floppy ears and curly tails predict the strength of behavioural correlations in support of the DS in 78 dog breeds. Contrary to the expectations of covariation among DS traits, we found that morphological traits did not covary among themselves, nor did they predict the strength of behavioural correlations among dog breeds. Further, the number of morphological traits in a breed did not predict the strength of behavioural correlations. Our results thus contrast with the hypothesis that the DS arises due to a shared underlying mechanism, but more importantly, questions if the morphological traits embedded in the DS are actual domestication traits or post-domestication improvement traits. For dogs, it seems highly likely that strong selection for breed specific morphological traits only happened recently in relation to breed formation. Present day dogs therefore have limited bearing of the initial selection pressures applied during domestication and we should reevaluate our expectations of the DS accordingly.

Population, sex and body size: determinants of behavioural variations and behavioural correlations among wild zebrafishDanio rerio

This study (1) investigated variation among populations and the effects of sex and body size on boldness, activity and shoal-association tendency among wild zebrafish, and (2) tested for existence of correlations between behaviours, controlling for sex and body size. Individuals across four natural populations were tested for general activity in a novel situation, number of predator inspections undertaken and tendency to associate with a conspecific shoal in the presence of predators. Results showed a significant effect of population on boldness with a population from high-predation habitat being bolder than populations from low-predation habitats. Males showed significantly higher tendencies than females to associate with a conspecific shoal in the presence of predators. Further, a negative relationship was found between activity and boldness only within two low-predation populations. Individual body size had a strong effect on the activity–boldness relationship within the low-predation population from flowing water habitat. Smaller fish were bolder and less active while larger fish were more cautious and active. Overall, the results indicated that while population-level behavioural responses might be shaped by predation pressure, state-dependent factors could determine behavioural correlations among individuals within populations.

Positive relationship between risk-taking behaviour and aggression in subordinate but not dominant males of a Cuban poeciliid fish

Studies of integrated phenotypes sometimes reveal correlations between mating effort, favoured by sexual selection, and risk-taking, favoured by survival selection. We used Girardinus metallicus to examine the relationship between rank order of mating effort and risk-taking. We measured risk-taking in a novel environment containing a predator. We then paired males, using aggression to assign dominant or subordinate status, and examined mating behaviour. Dominant males showed higher mating effort, but did not exhibit any relationship between risk-taking and mating effort. Subordinate males exhibited a cross-context correlation, as males were either more willing to take risks and aggressive or more hesitant to take risks and nonaggressive. Less risk-averse, aggressive subordinate males may gain fitness advantages in a more realistic dominance hierarchy, despite being outranked by the rival with which they were paired in our study. Results highlight intraspecific variation in behavioural correlations and the importance of social environment in shaping integrated phenotypes.