Innovation and elaboration on the avian tree of life

Abstract

Widely documented, megaevolutionary jumps in phenotypic diversity continue to perplex researchers because it remains unclear whether these marked changes can emerge from microevolutionary processes. Here, we tackle this question using new approaches for modeling multivariate traits to evaluate the magnitude and distribution of elaboration and innovation in the evolution of bird beaks. We find that elaboration, evolution along the major axis of phenotypic change, is common at both macro- and megaevolutionary scales, whereas innovation, evolution away from the major axis of phenotypic change, is more prominent at megaevolutionary scales. The major axis of phenotypic change among species beak shapes at megaevolutionary scales is an emergent property of innovation across clades. Our analyses suggest that the reorientation of phenotypes via innovation is a ubiquitous route for divergence that can arise through gradual change alone, opening up further avenues for evolution to explore.

Evolutionary bursts drive morphological novelty in the world’s largest skinks

“…We then ran PCA on (1) all traits jointly across all species and across (2) individual modules and (3) clades separately, then fit linear models to the first 2 PC axes (always accounting for ≥ 90% of variance). This allowed us to identify the major axes of elaboration (PC1) and innovation (PC2) following the language of Endler 12 and Guillerme et al 13 11_Innovate_Elaborate.R. We then identify change between parent and child node pairs as primarily elaborative or innovative by estimating the angle/slope of change of the line connecting them in Euclidean space (Fig.S16) and indicated by color.…”

“…However evolution is not limited to the major axis, and trajectories along minor axes may also pave a path towards new phenotypes. These competing processes are sometimes called “elaboration” ( along major axis) and “innovation” ( away from major axis) 12,13 . However their relative contributions towards organismal macroevolution and the evolution of novel forms has been largely overlooked 13–15 .…”

“…These competing processes are sometimes called “elaboration” ( along major axis) and “innovation” ( away from major axis) 12,13 . However their relative contributions towards organismal macroevolution and the evolution of novel forms has been largely overlooked 13–15 .…”