Figure 5:

Mammalian life history results. A) Posterior summary of the loadings. Loadings of body size onto factors 2–5 is set to 0 a priori. See Figure 3B for detailed description of figure elements. The first factor captures allometric relationships (by design) and explains only 16% of the heritable variance, while the remaining factors capture size-independent relationships. The second factor, accounting for the plurality (46%) of the heritable variance, captures a fast-slow life history axis. Remaining factors capture more specific strategies (e.g. factors three and four appear to support the energy trade-off between litter size and litter frequency). This suggests that body size is not the main driver of life history evolution and that natural selection primarily acts on life history directly. B) Evolution of factors along the mammalian phylogeny. Most factors are strongly phylogenetically conserved throughout the tree, with large clades sharing similar factor values. There is relatively little correlation between the the first and second factors, with clades of small, slow species (e.g. bats) and large, fast species (e.g. lagomorphs).