A nice review of genetic pest management (GPM) strategies for invasive species, by Tim Harvey-Samuel, Thomas Ant & Luke Alphey (of Oxitec fame), is presented in the recent issue of Biological Invasions.
I spent a lot of time reviewing the GPM literature back in 2012 and 2013, but I haven’t kept up to date on many of the technological advances, and it seems there has been a TON of progress in just that short amount of time. As the authors indicate, most of the new GPM strategies/technologies have been promoted/used in the context of insect-vectored diseases like dengue. But there are clearly many other problems that invasive species cause, and GPM could provide solutions. They suggest several areas where GPM could be useful, including in some vertebrate systems, like invasive island rats and the brown tree snake. The authors give a nice primer on several GPM techniques, covering both self-limiting and self-sustaining strategies, and they outline the different potential goals of either population replacement or population suppression.
I was surprised to see in this review a brief discussion of Philornis downsi, an introduced dipteran parasite of birds in Galápagos. Several other non-GPM strategies are being considered for management of P. downsi, including insecticide treated nesting materials and classical biological control. It seems unlikely that any of the newer GPM technologies would get a first trial in Galápagos; although perhaps something like RIDL would be deemed tested enough. However, it is my understanding that mass rearing of P. downsi continues to be problematic, hindering attempts to develop an SIT program, so P. downsi may be a particularly difficult system for a GPM program to develop. Nevertheless, I appreciate that Harvey-Samuel et al. (2017) are highlighting species of conservation concern.
Figure caption for image shown above: “Aromatase SRD [sex ratio distortion]: All F1 progeny will be phenotypically male, however 50% will carry female sex chromosomes (XX) “pseudomales”. In the F2 generation, 75% of progeny produced by heterozygous XY males will develop as phenotypic males (XX heterozygotes converted to pseduomales) while XX psedomales will prduce progeny at a 50:50 phenotypic sex ratio” (Harvey-Samuel et al. 2017).