In a new paper that will appear in Nature tomorrow, Walter Jetz and Colleagues “present, analyse and map the first complete dated phylogeny of all 9,993 extant species of birds, a widely studied group showing many unique adaptations.” The emphasis here is on the word “dated” – the study provides estimated diversification rates across the avian tree (Fig.1) as well as their geographic variation (Fig.2).
There are a number of very interesting results. For one, the overall diversification rate has increased over time. Jetz et al. note
We find that birds have undergone a strong increase in diversification rate from about 50 million years ago to the near present. This acceleration is due to a number of significant rate increases, both within songbirds and within other young and mostly temperate radiations including the waterfowl, gulls and woodpeckers. Importantly, species characterized with very high past diversification rates are interspersed throughout the avian tree and across geographic space.
Also, there are some interesting geographical patterns:
Geographically, the major differences in diversification rates are hemispheric rather than latitudinal, with bird assemblages in Asia, North America and southern South America containing a disproportionate number of species from recent rapid radiations. The contribution of rapidly radiating lineages to both temporal diversification dynamics and spatial distributions of species diversity illustrates the benefits of an inclusive geographical and taxonomical perspective. Overall, whereas constituent clades may exhibit slowdowns, the adaptive zone into which modern birds have diversified since the Cretaceous may still offer opportunities for diversification.
Really exciting, looking forward to study the paper in more detail.
Figure 2: Geographic variation in species-level lineage diversification rate and the richness of high-diversification rate species. Left: mean assemblage diversification rate. Right: relative (d) and absolute (e) richness of top 25% diversification rate species. (f) shows the richness of all 9,993 bird species for comparison.