Tough life in the tropics

摘要

The tropics host a much smaller number of invasive species than temperate regions, possibly because predation in the tropics is more intense. Amy Freestone of Temple University in Philadelphia, Pennsylvania, and her colleagues conducted field experiments off the coast of Connecticut and Panama. They allowed populations of non-native tunicates (pictured) - sessile marine creatures also known as sea squirts - to grow on plastic plates, blocked predators such as crabs and fish from reaching some of the plates, and looked at the effects of predation on species richness.