The Endangered Species Act lists ~900 species of plants within the U.S. Factors contributing to decline are not fully understood or characterized in part due to the lack of knowledge of life history and demography. In general, plant life-history variation can be summarized in two axes; how fast the plant grows and its reproductive strategy. Given the strong relationship between plant functional traits and life histories, identifying the position of a given species/population along the axes of variation using functional trait data may allow missing life-history information to be approximated. Such information can facilitate the development of population models, to systematically evaluate hypothetical scenarios of viability, stress and/or management to determine the best strategy to follow in order to protect a given species or population. For instance, The National Research Council advises the use of population models in risk assessments of pesticides for species listed under the Endangered Species Act. Likewise, the Services are advised to incorporate population model projections in the development of recovery plans to increase success and objectivity. In both cases, the models require demographic data, which are often lacking for listed species.
In this study we ask two main questions. 1- What are the life history and demographic patterns of listed plants in the USA? 2- What are the most prevalent data gaps for listed plants? We use COMPADRE and TRY data bases to obtain demographic data and functional traits for listed species and compare these statistically.
Our preliminary results from the COMPADRE data base indicate that there are 31 listed species with demographic data. Among these, herbaceous perennials are the most common growth form, followed by annuals, shrubs and trees. Demographic parameters like long-term population growth rate, generation time, and net reproductive rate show some significant differences between listed and non-listed species. In addition, elasticity patterns between listed and non-listed species exhibit significant differences. Listed species tend to show higher elasticity values for growth and fecundity than non-listed plants, whereas non-listed species exhibited higher elasticity values for survival than listed species. In general, for both listed and non-listed species elasticity values for survival are higher than fecundity and growth, a pattern reported elsewhere. These results demonstrate the general plasticity of growth and fecundity indicating plants can sustain environmental stressors that alter these parameters. However, plants are more susceptible to stressors that alter their survival rates, suggesting that recovery plans should focus on addressing these stressors.