Testing the use of surrogate demographic information for endangered species management
All species listed under the U.S. Endangered Species Act are required to have recovery plans that describe the management actions and specify recovery criteria that determine when the species can be considered “recovered.” These species-specific recovery criteria can be developed using population viability analyses, however the majority of listed species lack sufficient demographic information to parameterize those models. A frequently recommended solution is to use surrogate information from biologically similar species with sufficient demographic data to assess extinction probability. We examined the feasibility of such a surrogate approach by examining whether certain biological traits can be used to predict demographic rates. We used data from the COMPADRE plant matrix database and Bayesian hierarchical modeling to quantify the relationship between biological characteristics and intrinsic rate of growth (λ) while controlling for phylogenetic relatedness.
We found that annual herbaceous species tended to have higher growth rates than longer-lived herbaceous and woody species, but organism size did not have a significant effect on intrinsic growth rate. The variance components showed that the greatest source of variation in growth rates was among populations within species, and that it was two times greater than the variation in growth rates among species. Our results suggested that growth rates are influenced more strongly by population-level characteristics, such as abiotic conditions or human disturbances at a particular site, rather than by species-level characteristics. Because demographic rates are site-specific and likely not generalizable across different locations for the same species or across different species, our findings do not support the use of surrogate information for conservation decision-making.