On the consequences of ignoring purging on genetic recommendations for minimum viable population rules

Abstract

In conservation practice, preliminary assessments of extinction risk as well as emergency decisions are often based on scarce information. Thus, a simple 50/500 rule of thumb has been applied for a long time as a guidance to determine when genetic threats become relevant to conservation, and to settle the genetic threshold to the minimum size for population viability (the so-called MVP). This rule, used, for example, in the elaboration of the International Union for the Conservation of Nature Red List criteria for threatened species, states that the effective population size (Ne) should be at least 50 to prevent the dramatic consequences from inbreeding depression in the short term, whereas a larger value (Ne 500) would be needed to preserve adaptive potential in the long term (Franklin, 1980; Jamieson and Allendorf, 2012). As it is well known, these Ne values imply considerably larger censuses.