Plague bacterium as a transformer species in prairie dogs and the grasslands of western North America.

Invasive transformer species change the character, condition, form, or nature of ecosystems and deserve considerable attention from conservation scientists. We applied the transformer species concept to the plague bacterium Yersinia pestis in western North America, where the pathogen was introduced around 1900. Y. pestis transforms grassland ecosystems by severely depleting the abundance of prairie dogs (Cynomys spp.) and thereby causing declines in native species abundance and diversity, including threatened and endangered species; altering food web connections; altering the import and export of nutrients; causing a loss of ecosystem resilience to encroaching invasive plants; and modifying prairie dog burrows. Y. pestis poses an important challenge to conservation biologists because it causes trophic-level perturbations that affect the stability of ecosystems. Unfortunately, understanding of the effects of Y. pestis on ecosystems is rudimentary, highlighting an acute need for continued research.

La Bacteria de la Peste como una Especie Transformadora en los Perritos de las Praderas y los Pastizales del Oeste de Norteamérica Resumen Las especies invasoras transformadoras cambian el carácter, la condición, la forma o la naturaleza de los ecosistemas y merecen atención considerable por parte de los científicos de la conservación. Aplicamos el concepto de especie transformadora a la bacteria de la peste Yersinia pestis en el oeste de Norteamérica, en donde el patógeno fue introducido alrededor de 1900. Y. pestis transforma los ecosistemas de pastizal al disminuir severamente la abundancia de los perritos de las praderas (Cynomys spp.) y por lo tanto causa declinaciones en la abundancia y diversidad de las especies nativas, incluidas las especies amenazadas y en peligro; altera las conexiones de las redes alimenticias; altera la importación y exportación de nutrientes; causa la pérdida de resiliencia del ecosistema ante las plantas invasoras; y modifica las madrigueras de los perritos. Y. pestis es un reto importante para los biólogos de la conservación ya que causa perturbaciones de nivel trófico que afectan la estabilidad de los ecosistemas. Desafortunadamente, el entendimiento de los efectos de Y. pestis sobre los ecosistemas es rudimentario, lo que resalta una necesidad aguda de investigación continua.

Biomass-based targets and the management of multispecies coral reef fisheries.

The failure of fisheries management among multispecies coral reef fisheries is well documented and has dire implications for the 100 million people engaged in these small-scale operations. Weak or missing management institutions, a lack of research capacity, and the complex nature of these ecosystems have heralded a call for ecosystem-based management approaches. However, ecosystem-based management of coral reef fisheries has proved challenging due to the multispecies nature of catches and the diversity of fish functional roles. We used data on fish communities collected from 233 individual sites in 9 western Indian Ocean countries to evaluate changes in the site's functional composition and associated life-history characteristics along a large range of fish biomass. As biomass increased along this range, fish were larger and grew and matured more slowly while the abundance of scraping and predatory species increased. The greatest changes in functional composition occurred below relatively low standing stock biomass (<600 kg/ha); abundances of piscivores, apex predators, and scraping herbivores were low at very light levels of fishing. This suggests potential trade-offs in ecosystem function and estimated yields for different management systems. Current fishing gear and area restrictions are not achieving conservation targets (proposed here as standing stock biomass of 1150 kg/ha) and result in losses of life history and ecological functions. Fish in reefs where destructive gears were restricted typically had very similar biomass and functions to young and low compliance closures. This indicates the potentially important role of fisheries restrictions in providing some gains in biomass and associated ecological functions when fully protected area enforcement potential is limited and likely to fail. Our results indicate that biomass alone can provide broad ecosystem-based fisheries management targets that can be easily applied even where research capacity and information is limited. Of particular value, is our finding that current management tools may be used to reach key ecosystem-based management targets, enabling ecosystem-based management in many socioeconomic contexts.