Evidence does not support the targeting of cryptic invaders at the subspecies level using classical biological control: the example of Phragmites.

Kiviat, E. et al. (2019). Evidence does not support the targeting of cryptic invaders at the subspecies level using classical biological control: the example of Phragmites. Biol Invasions 21, 2529–2541. PDF

Summary

Kiviat et al respond to a recent paper in which Casagrande et al. suggest that two moth species (Archanara geminipuncta and A. neurica) could be used as biocontrol agents for non-native, invasive lineages of giant reed, Phragmites australis. Vetting potential biocontrol agents for specificity and negative effects on host species is already difficult. Although there are success stories, there are examples of biocontrol agents expanding their host range and damaging native species. The authors describe how the proposed biocontrol agents could expand their host range to include native Phragmites via pre-adaptation (ecological fitting) or rapid evolution. Although negative effects of non-native Phragmites are well-documented, in some sites they provide many ecological services such as sequestration of nutrients in eutrophic environments and protection from coastal erosion with sea level rise.

Take home points

  • Biocontrol is inherently risky and typically requires extensive research that demonstrates both negative effects and specificity to the target organism and a low potential for harm to the introduced habitats.

  • The proposed biocontrol agents are likely to incorporate native Phragmites into their host range, potentially damaging imperiled native populations.

Management implications

  • Biocontrol agents are not site-specific: biocontrol could impact populations of non-native (and native) Phragmites at all sites.

  • Removal of non-native Phragmites may negatively impact ecosystem services or cause collapse of wetland ecosystems in some sites.

Keywords

Impact Study; Range Expansion; Ecosystem services; Herbivory; Host Switching; Invasive species; Non-target impacts of biocontrol; Phragmites australis