PUBLIC RELEASE DATE:

1-Dec-2014

Contact: Jim Erickson ericksn@umich.edu 734-647-1842 University of Michigan @umich

ANN ARBOR - Charles Darwin noted more than 150 years ago that animals on the Galapagos Islands, including finches and marine iguanas, were more docile than mainland creatures. He attributed this tameness to the fact that there are fewer predators on remote islands.

While "island tameness" is an old idea, there have been few rigorous studies of the phenomenon. Many aspects remain unclear, including the mechanisms behind it and the speed at which it evolves in island populations.

A new University of Michigan-led study of Aegean wall lizard populations on 37 Greek islands shows that island tameness is determined by both the diversity of the local predator populations and the length of time an island has been separated from the mainland.

The researchers found that as the diversity of predators on an island increases, so does the distance at which these small lizards start to flee when they are approached -- an anti-predator response which scientists call the flight initiation distance. In addition, they found that the longer an island has been isolated from the mainland, on average, the longer its resident Aegean wall lizards will wait before fleeing from a predator.

The results suggest that animals living on small, long-isolated islands face the greatest risk from introduced predators -- such as feral cats and rats -- and should therefore receive priority in conservation efforts, said U-M vertebrate ecologist Johannes Foufopoulos, co-author of a paper scheduled for online publication in the journal Evolution on Dec. 1.

"Being so fearless, these populations are extremely susceptible to any novel predator that's introduced. In fact, island tameness has caused numerous island-species extinctions at the hands of human-introduced predators and pets," said Foufopoulos, an associate professor at the U-M School of Natural Resources and Environment.

"Determining what factors lead to the loss of effective anti-predator responses is critical because it provides a fundamental understanding of evolutionary processes on islands and also helps conservation managers predict which island species are at most risk," he said.

Original post:

Predators and isolation shape the evolution of 'island tameness,' providing conservation insights