Inbreeding depression in the predatory mite Stratiolaelaps scimitus: demographic and transcriptomic insights

The consequences of inbreeding in haplodiploid species remain a subject of debate, with some studies suggesting minimal effects due to purging of deleterious alleles, while others report clear evidence of inbreeding depression. This uncertainty has important implications for the mass rearing of biological control agents such as Stratiolaelaps scimitus (Womersley) (Acari: Laelapidae). Here, we examine the effects of 30 generations of sibling inbreeding on the life-history traits and transcriptomic profiles of Stratiolaelaps scimitus.

Inbreeding significantly altered multiple fitness-related traits. Inbred females exhibited extended lifespans, possibly reflecting trade-offs in resource allocation, while inbred males had reduced longevity. Reproductive performance was compromised, with delayed onset of reproduction and reduced fecundity. Transcriptomic analysis revealed widespread gene expression changes, including dysregulation of pathways involved in morphogenesis, oxidative stress response, and intracellular metabolism.

These results provide empirical support for the occurrence of inbreeding depression in Stratiolaelaps scimitus, despite its haplodiploid genetic system. The observed physiological and molecular impairments highlight the need for routine genetic management. We recommend periodic outcrossing in commercial rearing programmes to maintain colony health and ensure the long-term efficacy of this species as a biocontrol agent. © 2025 Society of Chemical Industry.