Reestablishment of a Keystone Species: Initial Outcomes and Ecosystem Responses

Abstract

The keystone species concept was introduced in 1969 in reference to top-down regulation of communities by predators, but has expanded to include myriad species at different trophic levels. Keystone species play disproportionately large, important roles in their ecosystems, but human-wildlife conflicts often drive population declines. A prominent example of anthropogenically driven keystone species decline is the prairie dog (Cynomys spp.) in North America. Prairie dogs were once widespread, but were considered pests and eradicated throughout much of the North American west; however, prairie dogs are keystone species that maintain the organization and diversity of their ecosystem, thus their removal can have a cascade of effects on the environment. Population declines have resulted in the necessity of keystone species reintroductions, however, studies of such reintroductions are rare. Managers have reintroduced prairie dogs as a grassland conservation tool, but often do not monitor populations intensively enough following reintroduction to accurately determine success. Furthermore, most studies of keystone species do not assess ecosystem-level effects of reestablishment. I studied four recently reestablished black-tailed prairie dog (Cynomys ludovicianus) colonies to determine if the reestablishment effort was successful, and if keystone roles were resumed after a prolonged absence. I found that two of three prairie dog populations monitored for demography grew, and three of four prairie dog colonies expanded in area. Furthermore, I found that reestablished black-tailed prairie dogs did not immediately influence small mammal diversity, richness, or abundance, but prairie dogs did resume their keystone role of regulating woody plant growth on colonies.