Geographic range size and evolutionary age in birds

Area of Science:

• Evolutionary Biology
• Biogeography
• Ornithology

Background:

• Species range-size distributions are shaped by speciation, extinction, and post-speciation range transformations.
• Directly studying evolutionary range-size dynamics has been methodologically challenging, leading to theoretical models.
• Understanding range-size changes is crucial for ecological and evolutionary dynamics.

Purpose of the Study:

• To investigate the relationship between species age and global geographic range size in birds.
• To determine if avian range sizes change dynamically over evolutionary time.
• To test proposed models of range-size dynamics.

Main Methods:

• Utilized molecular data to estimate species ages in six avian monophyletic groups.
• Examined the correlation between estimated species age and current global geographic range size.
• Analyzed patterns of range expansion and contraction relative to speciation events.

Main Results:

• Provided strong evidence that avian geographic range sizes are not static throughout evolutionary history.
• Demonstrated that range-size transformations in birds are generally non-random.
• Observed a pattern of initial rapid range expansion post-speciation, followed by a more gradual decline with increasing species age.

Conclusions:

• Avian species ranges undergo significant, non-random transformations over evolutionary timescales.
• The observed pattern supports models where ranges expand after speciation and subsequently contract.
• These findings offer empirical insights into the long-term dynamics of species distributions.