The global diversity of birds in space and time

Abstract

Current global patterns of biodiversity result from processes that operate over both space and time and thus require an integrated macroecological and macroevolutionary perspective. Molecular time trees have advanced our understanding of the tempo and mode of diversification and have identified remarkable adaptive radiations across the tree of life. However, incomplete joint phylogenetic and geographic sampling has limited broad-scale inference. Thus, the relative prevalence of rapid radiations and the importance of their geographic settings in shaping global biodiversity patterns remain unclear. Here we 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. 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. 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.

The evolution of sex roles in birds is related to adult sex ratio

“…These results are not sensitive to a specific phylogenetic hypothesis, or potentially confounding variables. The aforementioned results are highly consistent between alternative phylogenetic hypotheses and different branch-length assumptions: the four key tests remain highly significant by using 100 randomly selected trees from the most recent avian phylogeny 20 ( Supplementary Fig. S1), or using alternative phylogenies of shorebirds (Supplementary Table S1).…”

“…First we re-run the key PGLS models using a sample of 100 trees from the most recent comprehensive avian phylogeny 20 to which we added C. nivosus as described above ( Supplementary Fig. S1).…”

Five palaeobiological laws needed to understand the evolution of the living biota

“…For example, analysis of lineage through time (LTT) plots derived from molecular phylogenies are often used to conclude that living groups are in the midst of ongoing radiations, especially if they show steady or increasing rates of diversification (Fig. 1a), as has been hypothesized for birds 48 and cetaceans 49 . However, there is a wide range of diversity trajectories, including long-term species loss 50 , that can lead to very similar LTT plots 26,31 , once the extinct species are removed.…”

Combining phylogenomic and supermatrix approaches, and a time-calibrated phylogeny for squamate reptiles (lizards and snakes) based on 52 genes and 4162 species

“…Another extreme approach is to include hundreds or thousands of species but for a smaller number of genes: this is the typical approach in supermatrix studies (e.g. Pyron and Wiens, 2011;Jetz et al, 2012;Pyron et al, 2013). Whether it is better to sample more taxa or more genes to resolve higher-level phylogenies was once a major debate in systematics (e.g.…”