Innovation and elaboration on the avian tree of life across evolutionary scales

The origins of biological diversity remains a central question in mega-, macro- and micro-evolutionary biology. A long-standing proposal is that the majority of diversity at the species level and at nested taxonomic levels arises from elaboration - where new species’ traits evolve along an ‘evolutionary line of least resistance’.

An alternative is that diversity can arise via innovation - where species evolve orthogonally to that ‘line of least resistance’. Here we apply new multi-trait methods to evaluate the magnitude and distribution of elaboration and innovation among superorders, orders and species of birds. Our analyses reveal that diversification has arisen via different patterns of elaboration and innovation at all scales.

Furthermore, we reveal a nested structure of these patterns at the mega-, macro- and micro-evolutionary levels. These results suggest that both elaboration and innovation are ubiquitous across evolutionary scales and that our new method can be used to unpick heterogeneous patterns in the origins and maintenance of biodiversity.