Reintroduction of Castilleja levisecta: Effects of ecological similarity, source population genetics, and habitat quality

A suite of ecological and genetic factors are likely to contribute to reintroduction performance. Potential factors include the ecological similarity between seed source and introduction site, population size and genetic diversity of seed sources, and the habitat quality of the introduction site. We conducted common garden experiments with golden paintbrush (Castilleja levisecta), an endangered species from the Pacific Northwest, U.S.A., in order to test hypotheses about reintroduction performance and to provide management recommendations. Ten common gardens, each composed of C. levisecta individuals grown from seed from six of the remaining populations, were planted into field conditions and monitored during two growing seasons. Plant community characteristics were important predictors of observed variation in C. levisecta performance. Exotic species-cover at common garden sites was associated with a reduction in performance of first-year C. levisecta transplants, while survival to the second growing season increased with increasing similarity in plant functional groups between source and common garden sites. Although measures of genetic diversity, population size, and geographic distance are often used to make conservation decisions during species recovery, here they were poor predictors of C. levisecta performance and establishment. We recommend choosing material for reintroduction from ecologically similar habitats, rather than those most proximate geographically, and selecting recovery sites with low exotic species abundance.