EFFECT OF NEW FOUNDERS ON RETENTION OF GENE DIVERSITY IN CAPTIVE POPULATIONS - A FORMALIZATION OF THE NUCLEUS POPULATION CONCEPT

A nucleus population is a small captive population genetically support ed by periodic importation of wild caught animals. Periodic importatio n will allow nucleus populations to maintain the same amount of gene d iversity as larger captive populations that do not import wild caught animals. The function of nucleus populations as envisioned by the IUCN /SSC Captive Breeding Specialist Group (CBSG) is to make additional ca ptive space available for endangered taxa not currently maintained in captivity. In this article, mathematical models are developed to asses s the effectiveness of the nucleus population concept in reducing the population sizes necessary to maintain appreciable amounts of gene div ersity in captive populations. It is shown that the Nucleus I populati on concept, as defined and promoted by the CBSG, requires an importati on rate 10-20 times greater than they have indicated. Whereas nucleus populations are not appropriate for maintenance of significant amounts of gene diversity in long-term breeding programs, small populations c an be valuable for research, education, and reintroduction projects wi th short-term goals. Decisions have to be made on which of the many en dangered taxa will be maintained and for what purposes, if captive bre eding is to be an effective component of species conservation. (C) 199 3 Wiley-Liss, Inc.