Last updated August 15, 2018 at 4:43 pm
Isolation requires more elaborate behavioural responses.
A female NZ Tomtit (Petroica macrocephala). It’s specific name means “big head”, referring to its large head in comparison to other members of its genus. Credit: Jon Sullivan
Birds living on isolated islands are smarter because they have to be, according to new research.
Scientists from Spain, Sweden and Canada have discovered that species found on oceanic islands – islands that rise from the ocean floor due to seismic or volcanic activity – have larger brains than mainland relatives.
And their results suggest the differences are the result of evolutionary processes rather than simply varied colonisation success.
They believe island living makes the environment more unpredictable, which in turn selects for larger brains. On islands, there are limited possibilities to disperse when conditions deteriorate, which may force individuals to explore and rely on more elaborate behavioural responses.
They point to the use of tools by the New Caledonian crow, the Hawaiian crow and the Galapagos woodpecker as examples of evolved advanced cognitive abilities.
Implications for adaptive radiations
The researchers studied 11,554 specimens from 1931 bird species – 110 living on oceanic islands and 1821 on the mainland – and suggest their findings have implications for adaptive radiations on islands.
“Behavioural shifts combined with geographic isolation may be powerful forces driving evolutionary changes through divergent selection,” they write.
“However, unlike the flexible stem hypothesis, which predicts that adaptive radiations should be enhanced by behaviourally flexible ancestors able to occupy a broader niche, our results suggest that selection for enhanced flexibility (as measured by brain size increases) may also occur on islands instead of being exclusively derived from ancestral species.
“Ecological opportunities, geographic isolation and particular gene architectures can influence rapid evolutionary diversification on islands, but our findings highlight that to unravel why some vertebrates have experienced such extraordinary adaptive diversifications on islands we also need to consider brain evolution.”
The paper published in Nature.
