Impact of long-term mass-rearing on the genetic structure of tsetse fly Glossina palpalis gambiensis colonies.

Abstract

Tsetse flies are the sole cyclic vectors of African trypanosomes, which cause human and animal African trypanosomiases in Africa. Tsetse fly control remains a promising option for disease management. The sterile insect technique (SIT) stands as an environmentally friendly tool to control tsetse populations. SIT requires the mass-rearing of competent sterile males to mate with wild females. However, long-term colonization might affect the genetic structure of the reared flies. This study investigated the genetic structure of four Glossina palpalis gambiensis colonies of different ages: two originating from Senegal (SEN and ICIRSEN) and two from Burkina Faso (CIR and IBD). Samples from these colonies were genotyped at ten microsatellite loci, followed by downstream population genetic analyses. The results show that the two colonies from Burkina Faso collected from close sites (∼20 km apart) over 45-year interval retained the same genetic background (F_{ST_CIR∼IBD} ≈ 0, P-value = 0.47). These flies were however, genetically different from those from the Senegal colonies (F_{ST_CIR∼SEN} ≈ 0.047; F_{ST_IBD∼SEN} ≈ 0.058, P-value = 10^-4). Moreover, no significant difference was detected in the gene diversity of the CIR and IBD colonies, with H_S values of 0.650 and 0.665, respectively. The inbreeding coefficient showed that all four colonies where under Hardy-Weinberg equilibrium, with F_IS values of 0.026, 0.012, -0.064, and 0.001, for CIR, IBD, ICIRSEN, and SEN, respectively. Furthermore, no sign of a recent bottleneck was identified in tsetse samples from any of the four colonies. The results suggest that long-term mass-rearing of tsetse flies has no significant impact on their genetic background and diversity.