The function of zebra stripes by Tim Caro et al. just published in Nature Communications is a neat paper that I came across this afternoon and felt like sharing. It does a good job demonstrating the power and simplicity of comparative analyses.
Essentially, why zebras have stripes has been an elusive riddle for over a century. Caro et al. set out to solve this once and for all. They tested whether striping has arisen due to camouflage, as an anti-predator disruption, for heat management, or to benefit social interactions. But it is their fifth hypotheses – avoidance of biting tsetse flies – that seems to gain the most support. This came from predicting striping on different parts of the zebra’s body simply by fitting phylogenetic generalized least-squares models with different covariates. It goes a long way to show how a well-founded set of hypotheses around the function of traits and morphological characters can be inferred from modelling observational data. Although there is no substitute for a good experiment, like placing model horses in fly-infested fields, experiments that test multiple co-occurring mechanisms are challenging!