The use of surrogate species in risk assessment: predicting reliability using life history data

The use of surrogate species is an important tool in predicting the effects of management decisions or the establishment of protective measures for endangered/threatened species. While relying on a handful of model species to predict the fate of scores of distantly-related target species has been recently criticized, a quantitative measure linking limiting similarities in life history traits and population predictions has been sorely missing. We present here a mathematical model that facilitates determining when surrogate species population outcomes will reliably predict outcomes of target (listed) species. We develop an inequality that indicates how dissimilar life history traits (survival & fecundity) of the surrogate and listed species may be before the surrogate species outcomes indicate a positive population growth, whereas the listed species is driven to extinction (e.g., a “false negative”). We illustrate the use of this quantitative test by incorporating arthropod life history data into the derived expression, and discuss further applications in risk assessment as well as pest management and conservation efforts. Our approach should prove useful to a wide range of age- or stage-structured population models.