Fig. 7.

Pathway 5 Biodiversity: Potential horizontal gene flow of the dsxF^CRISPRh transgene to a NTO eukaryote could lead to its unintended population suppression, thus reducing densities of valued species or ecosystem services. The An. gambiae complex is considered to be made up of nine cryptic species, namely An. amharicus, An. arabiensis, An. bwambae, An. coluzzii, An. fontenillei, An. gambiae s.s., An. melas, An. merus, and An. quadriannulatus [48–52]. Because the guide RNA target sequence of the dsxF^CRISPRh transgene that are conserved in all of the above species examined [17], transfer of this transgene between any of these species via hybridization would likely lead to functional gene drive and population suppression in those species. Thus, all of the above species are considered TOs. The most closely related species to An. gambiae is An. christyi which differs morphologically, and is genetically distinct, from An. gambiae, with both species being separated by circa 9 million years of evolution [72]. The absence of observed gene flow between both species supports the lack of any significant hybridization between these species so that for even less closely-related species of Anopheles hybridization with An. gambiae is considered implausible. Hybridization is therefore not considered a plausible mechanism for transfer of the gene drive transgene from An. gambiae to NTOs including valued species