"Researchers assessed four species -- three lizards and a bird -- in the Santa Monica Mountains near Thousand Oaks. Co-author Robert Fisher at the U.S. Geological Survey in San Diego said a similar study recently was started in San Diego County to see what has happened to genetic diversity in a region where habitat "connectivity" and conservation planning goes back several years.
His work in the Santa Monica Mountains suggests "habitat islands" are forming where animals are unlikely to be related to the same species in neighboring areas. In addition, animals within smaller and more-isolated habitat patches are closely related to one another."
Roads and other human-made barriers tend to isolate animals and encourage in-breeding, which reduces biodiversity and potentially increases the risk of extinction.