Groups of animals possess phenotypes such as collective behaviour, which may determine the fitness of group members. However, the stability and robustness to perturbations of collective phenotypes in natural conditions is not established. Furthermore, whether group phenotypes are transmitted from parent to offspring groups with fidelity is required for understanding how selection on group phenotypes contributes to evolution, but parent-offspring resemblance at the group level is rarely estimated. We evaluated the repeatability, robustness to perturbation, and parent-offspring resemblance of collective foraging aggressiveness in colonies of the social spider Anelosimus eximius. Among-colony differences in foraging aggressiveness were consistent over time but changed if the colony was perturbed through the removal of individuals, or via individuals’ removal and subsequent return. Offspring and parent colony behaviour were correlated at the phenotypic level, but only once the offspring colony had settled after being translocated, and the correlation overlapped with zero at the among-colony level. The parent-offspring resemblance was not driven by a shared elevation but could be due to other environmental factors. The behaviour of offspring colonies in a common garden laboratory setting was not correlated with the behaviour of the parent colony nor the same colony’s behaviour once it was returned to the field. The phenotypes of groups represent a potentially important tier of biological organisation, and assessing the stability and heritability of such phenotypes helps us better understand their role in evolution.

For full data collection and analysis methods, please see the associated paper. But in brief:

 

We located 45 colonies of social spiders (Anelosimus eximius) in Ecuador, and repeatedly assayed them for behaviour. We then removed some spiders from 2/3 of them (the "disturbance"), and tested those subsets in a laboratory. We then returned 15 subsets back to their original colony, and the other 15 were placed into vegetation within 5-10m of the original colony ("bud" colonies). We then assayed both the original colonies and the newly founded colonies repeatedly.

 

To analyse it we used multivariate mixed effect models in the R package "MCMglmm" to determine the among colony covariance in foraging aggression between pre- and post-disturbance assays, and if this differed between colonies that had individuals removed, individuals removed and then returned, and colonies that were not disturbed. We also related pre-disturbance assays to tests in the laboratory and to the assays on the bud colonies.

See ReadMe file ("Herit & robust to disturb ReadMe.docx") and R code file ("Herit & robust to disturb R code.R") for how to use the dataset