A corollary of Darwin's revolutionary idea was that organisms would also evolve to lose structures, functions, and behaviors they no longer needed when environmental circumstances changed, researchers said. (Agencies)
Darwin noted that island animals often acted tame, and presumed that they had evolved to be so after coming to inhabit islands that lacked most predators.
But more than 150 years later that almost casual observation remained to come under scientific scrutiny.
A team of researchers have now showed that island lizards are indeed "tame" as compared with their mainland relatives. The researchers were able to approach island lizards more closely than they could approach mainland lizards.
"Our study confirms Darwin's observations and numerous anecdotal reports of island tameness," said Theodore Garland, a professor of biology at University of California, Riverside and one of the paper's co-authors.
"His insights have once again proven to be correct, and remain an important source of inspiration for present-day biologists," said Garland.
The researchers conducted analyses of relationships of flight initiation distance (the predator–prey distance when the prey starts to flee) to distance to mainland, island area,
and occupation of an island for 66 lizard species, taking into account differences in prey size and predator approach speed.
They analysed island and mainland lizard species from five continents and islands in the Atlantic and Pacific Oceans and the Caribbean and Mediterranean Seas.
Their results showed that island tameness exists and that flight initiation distance decreases as distance from mainland increases.
In other words, island lizards were more accessible the farther the islands were from the mainland, researchers said.
A corollary of Darwin's revolutionary idea was that organisms would also evolve to lose structures, functions, and behaviors they no longer needed when environmental circumstances changed, researchers said.