Mark Davis et al. set an unrealistically high bar for those making management decisions about exotic species (Nature 474, 153–154; 2011). Control is often easier, cheaper and more effective soon after detection (R. A. Haack et al. Annu. Rev. Entomol. 55, 521–546; 2010). We agree that research on ecosystem impact is necessary, but such studies can take years.

Meanwhile, we suggest that control priorities for potential invasive species could be based on easily available data about natural history and evolutionary ecology. We propose four guidelines for identifying such invasives.

An exotic organism may be more likely to invade and cause disruption the greater its rate of reproduction; the greater its dispersal ability; the closer (phylogenetically) its preferred food in its native range is to an abundant taxon in the new range; and the farther away (phylogenetically) its predators and pathogens are in its native range from those in its new range.

For example, the red turpentine beetle (Dendroctonus valens) is not particularly disruptive in its native range in North America because it attacks only trees that are already weakened. In China it attacks and kills healthy trees (Z. Yan et al. Biodivers. Conserv. 14, 1735–1760; 2005). The reasons for this beetle's success as an invasive include its high dispersal and reproductive rates, its affinity for Chinese pines closely related to those it feeds on 'at home', and the lack of predators or pathogens phylogenetically similar to ones found in North America.