Demographic History of the Bird Family Calcariidae
North American open habitats, including Arctic tundra and temperate grasslands, have undergone cyclical expansions and contractions since the mid Pliocene, driven by glacial interglacial dynamics. These climatic oscillations drove substantial latitudinal and geographic shifts in both habitat types. The bird family Calcariidae is thought to have originated and diversified within these environments during this period of climatic change and habitat shift. Species in this family use open habitats in three ways: as grassland specialists, as migratory species that breed in Arctic tundra and winter in grasslands (mixed-habitat users), or as permanent tundra residents. To contextualize the timing of Calcariidae diversification, we inferred a time-calibrated Bayesian phylogeny from 23,272 biallelic sites. To evaluate how habitat specialization interacted with glacial interglacial cycles to influence avian demography, we reconstructed effective population size (Ne) trajectories using a coalescent Markovian model. Our results show that patterns of Ne variation closely correspond to habitat preferences: grassland specialists exhibited the highest Ne, mixed habitat users had intermediate values, and the Arctic tundra specialist had the lowest Ne. These demographic patterns were consistent with genetic diversity indices, indicating that habitat specialization has been a key driver of evolutionary and demographic trajectories within Calcariidae.
BioProject