Reproductive compatibility of a newly imported Australian population of the biocontrol agent Anaphes nitens with an existing South African population

Abstract

Introductions of natural enemies in classical biocontrol programs potentially cause genetic bottlenecks which can be detrimental for biocontrol. This can be mitigated by introducing multiple populations of a natural enemy, but thorough pre-release testing is needed to ensure compatibility. In this study compatibility between an established population of Anaphes nitens in South Africa and a newly imported A. nitens population from Australia was tested. Anaphes nitens is an egg parasitoid of Gonipterus sp. n. 2, an important pest in Eucalyptus plantations. South African and Australian A. nitens lineages were compared to two admixed lineages, which were reared from the F0 to the F2 generation. No differences were found in the proportion of replicates producing offspring overall, or female offspring specifically, indicating there was no sexual isolation between the populations. The typical symptoms of cytoplasmic incompatibility in haplodiploids, namely male biased sex ratios, were not observed. The lack of significant differences in fecundity and development time between the lineages suggested that there was no hybrid vigour or outbreeding depression. We conclude that a field release of the imported A. nitens population poses a low risk of disrupting the existing biocontrol program due to reproductive barriers or outbreeding depression. Whether there is a benefit of adding the newly imported Australian A. nitens population to the existing biocontrol system in South Africa needs to be studied further, for example by performing a field release combined with post-release assessments for determining establishment and spread.