June 19, 2018 by Hayley Dunning, Imperial College London
Extensive new datasets about the world's birds are helping to solve the riddle of how life on Earth diversified.
By combining global datasets on bird characteristics, citizen-science species sightings and genetics, researchers have begun to answer some key questions in biodiversity. The results are published today in Nature Ecology & Evolution, in two parallel studies that include Imperial College London researchers.
The first paper compiles body measurements and estimates of evolutionary history for hundreds of closely related bird species (called 'sister species') to study how new species evolve.
In most cases, new bird species begin to emerge when one population is isolated geographically from others, such as by a mountain range. Later, the diverging species may extend their geographical ranges, bringing them back into contact.
These encounters can play out in one of three ways: the species can interbreed and form a single species again; they can stay separated but with hard borders between their two ranges; or they can continue to expand their ranges until they coexist over a wide area.
What determines whether emerging species stay separate or coexist? The team, led by Dr. Jay McEntee at the University of Florida, used a vast citizen-science database of bird sightings worldwide to identify where sister species were seen in the same place at the same time, allowing the timing and extent of coexistence among sister species to be estimated.
Different traits allow coexistence
The researchers found that if sister species had very different traits that affect their way of life, such as beaks adapted to different foods, they were more likely to coexist sooner and over larger areas.
In contrast, those with very similar traits appeared not to overlap successfully. The researchers think this is because there is 'interference' between the species, such as interbreeding, or competition for resources like food.