How and why lineages evolve along niche space as they diversify and adapt to different environments is fundamental to evolution. Progress has been hampered by the difficulties of linking a robust empirical characterization of species niches with flexible evolutionary models that describe their evolution. Consequently, the relative influence of abiotic and biotic factors remains poorly understood. Here we characterize species’ two-dimensional temperature and precipitation niche space occupied (i.e., species niche envelope) as complex geometries and assess their evolution across all Aves using a model that captures heterogeneous evolutionary rates on time-calibrated phylogenies. We find that extant birds coevolved from warm, mesic climatic niches into colder and drier environments and responded to the K-Pg boundary with a dramatic increase in disparity. Contrary to expectations of subsiding rates of niche evolution, our results show that overall rates have increased steadily, with some lineages experiencing exceptionally high evolutionary rates, associated with colonization of novel niche spaces, and others showing niche stasis. Both competition- and environmental change-driven niche evolution transpire and result in highly heterogeneous rates near the present. Our findings highlight the growing ecological and conservation insights arising from model-based integration of comprehensive environmental and phylogenetic information.

Climatic information was derived using publicly available global climatic data sets and processed using R to create polygons representing the climatic niche of all species of birds. This was used then as input to a BEAST analysis of 2D Relaxed Random Walk.

The Online Electronic Material includes the following files: 

1. source_datasets.txt: text data describing all the publicly available datasets used to reconstruct species climatic niche envelopes used.
2. extract_climatic_niches.r: R code used to extract bird climatic information and create their climatic niche envelopes.
3. Beast_run.xml: xml file use to run the analysis of climatic niche evolution.
4. MCCtree.tre: Maximum Clade Credibility tree holding the posterior information for the climatic niche evolution analysis, including per branch median and posterior Highest Posterior Density intervals for temperature, precipitation and rates of evolution.