Animal Conservation

Short Communication

How large must populations be to retain evolutionary potential?

I. R.  Franklin a1 and R.  Frankham a2
a1 CSIRO Division of Animal Production, Locked Bag 1, Blacktown, NSW 2148, Australia
a2 Key Centre for Biodiversity and Bioresources, School of Biological Sciences, Macquarie University, NSW 2109, Australia


Maintaining genetic variation for future evolutionary change is an important issue for conservation biology. However, there is controversy over the effective population size (Ne) required for endangered species to retain their evolutionary potential, with proposed sizes ranging from 500 to 5000. The highest estimate is based on the assumption that 90% of mutations are deleterious. We review the arguments for an effective size of 5000 and conclude that it assumes effective mutation rates that are too low, and heritabilities that are, in general, very high. We conclude that an Ne of 500–1000 is appropriate at this time.

(Received June 20 1997)
(Accepted December 3 1997)