XVI International Botanical Congess

Inbreeding depression (ID) critically influences mating system evolution and the persistence of small populations. Inbreeding may tend to purge populations of deleterious recessive mutations to reduce ID. The extent of purging depends on many population and genetic factors, making it impossible to make universal predictions. We review 52 studies that compare ID among groups inferred to differ in inbreeding history. Fourteen of 34 studies comparing ID among populations and species found significant evidence for purging. Within populations, 6 of 18 studies found evidence for purging among lineages. Regression analyses suggest that purging is most likely to ameliorate ID for early traits. However, meta-analysis revealed no evidence for purging. Perennials are unlikely to show purging. The results suggest that purging is an inconsistent force within populations.