Proc. R. Soc. B doi:10.1098/rspb.2009.1153 (2009)

The risk of a population becoming extinct is influenced more by environmental factors than by migration between subpopulations, according to Blaine Griffen, now at the University of South Carolina in Columbia, and John Drake of the University of Georgia in Athens.

To monitor extinction effects, they studied populations of the zooplankton Daphnia magna in small water tanks, each divided by a partition with holes of varying number and size to control the migration rate between the two chambers. The aquaria were stacked up in a lab, with higher tanks receiving more light. Migration had little effect on the length of time to extinction, but higher tanks receiving more light harboured larger populations that took longer to become extinct, the researchers found.