Minimización del riesgo de extinción mediante el rescate genético

According to the genetic rescue hypothesis, immigrants can improve population persistence through their genetic contribution alone. We investigate the potential for such rescue using small, inbred laboratory populations of the bean beetle (Callosobruchus maculatus). We ask how many migrants per generation (MPG) are needed to minimize the genetic component of extinction risk. During Phase 1, population size was made to fluctuate between 6 and 60 (for 10 generations). During this phase, we manipulated the number of MPG, replacing 0, 1, 3, or 5 females every generation with immigrant females. During Phase 2, we simply set an upper limit on population size (.10). Compared with the 0–MPG treatment, the other treatments were equivalently effective at improving reproductive success and reducing extinction risk. A single MPG was sufficient for genetic rescue, apparently because effective migration rate was inflated dramatically during generations when population size was small. An analysis of quasi–extinction suggests that replicate populations in the 1–MPG treatment benefited from initial purging of inbreeding depression. Populations in this treatment performed so well apparently because they received the dual benefit of purging followed by genetic infusion. Our results suggest the need for further evaluation of alternative schemes for genetic rescue.Según la hipótesis del rescate genético, los inmigrantes pueden mejorar la persistencia de una población mediante su contribución genética. Hemos investigado el potencial de un rescate de este tipo, utilizando pequeñas poblaciones endogámicas de laboratorio del gorgojo del haba Callosobruchus maculatus. Nos preguntamos cuántos migrantes por generación (MPG) son necesarios para minimizar el componente genético del riesgo de extinción. Durante la Fase 1, se hizo fluctuar el tamaño de la población entre 6 y 60 (durante 10 generaciones). En dicha fase manipulamos el número de MPGs, reemplazando 0, 1, 3, o 5 hembras nativas por hembras inmigrantes en cada generación. Durante la Fase 2, nos limitamos a poner un límite superior al tamaño de la población (.10). Comparados con el tratamiento de 0–MPG, los otros tratamientos resultaron ser igualmente efectivos en la mejora del éxito reproductivo y la reducción del riesgo de extinción. Un único MPG era suficiente para el rescate genético, aparentemente debido a que la tasa de migración efectiva quedaba espectacularmente sobredimensionada durante generaciones, cuando el tamaño de la población era pequeño. Un análisis de cuasi–extinción sugiere que las poblaciones replicadas durante el tratamiento 1–MPG se beneficiaron de un saneamiento inicial por la disminución de la endogamia. Aparentemente, las poblaciones de este tratamiento se comportaron tan bien debido a que recibieron el doble beneficio del saneamiento seguido de la inyección genética. Nuestros resultados sugieren la necesidad de posteriores evaluaciones del rescate genético mediante esquemas alternativos

Registration of VLF-sferics at the von-Neumayer Station

A VLF-sferics-analyzer was operating at the German antarctic station von-Neumayer from January to July 1983. This analyzer registrated far distant lightning events in the frequency range between 5 and 9kHz. Assuming the location of these sources to be known, the propagation characteristics of the atmospheric wave guide between the earth and the ionosphere can be derived along the propagation path. The method of measurement is described. The data of June 1983 are evaluated and the distances of the sources are determined from a comparison with rain fall records during the same month and, in addition, from sferics registrations obtained at a second station in Pretoria, South Africa. The main result is that the ionospheric D layer along the propagation paths from the east coast of South America to the von-Neumayer station and from South Africa to the von-Neumayer station do not show a significant daily variation. The virtual ionospheric reflection height is about 82km for VLF waves between 5 and 9kHz during June. This corresponds to night time conditions at northern mid-latitudes in winter

Minimizing extinction risk through genetic rescue

Abstract Minimizing extinction risk through genetic rescue.-According to the genetic rescue hypothesis, immigrants can improve population persistence through their genetic contribution alone. We investigate the potential for such rescue using small, inbred laboratory populations of the bean beetle (Callosobruchus maculatus). We ask how many migrants per generation (MPG) are needed to minimize the genetic component of extinction risk. During Phase 1, population size was made to fluctuate between 6 and 60 (for 10 generations). During this phase, we manipulated the number of MPG, replacing 0, 1, 3, or 5 females every generation with immigrant females. During Phase 2, we simply set an upper limit on population size (.10). Compared with the 0-MPG treatment, the other treatments were equivalently effective at improving reproductive success and reducing extinction risk. A single MPG was sufficient for genetic rescue, apparently because effective migration rate was inflated dramatically during generations when population size was small. An analysis of quasi-extinction suggests that replicate populations in the 1-MPG treatment benefited from initial purging of inbreeding depression. Populations in this treatment performed so well apparently because they received the dual benefit of purging followed by genetic infusion. Our results suggest the need for further evaluation of alternative schemes for genetic rescue. Key words: Extinction risk, Founder events, Genetic rescue, Inbreeding. Resumen Minimización del riesgo de extinción mediante el rescate genético.-Según la hipótesis del rescate genético, los inmigrantes pueden mejorar la persistencia de una población mediante su contribución genética. Hemos investigado el potencial de un rescate de este tipo, utilizando pequeñas poblaciones endogámicas de laboratorio del gorgojo del haba Callosobruchus maculatus. Nos preguntamos cuántos migrantes por generación (MPG) son necesarios para minimizar el componente genético del riesgo de extinción. Durante la Fase 1, se hizo fluctuar el tamaño de la población entre 6 y 60 (durante 10 generaciones). En dicha fase manipulamos el número de MPGs, reemplazando 0, 1, 3, o 5 hembras nativas por hembras inmigrantes en cada generación. Durante la Fase 2, nos limitamos a poner un límite superior al tamaño de la población (.10). Comparados con el tratamiento de 0-MPG, los otros tratamientos resultaron ser igualmente efectivos en la mejora del éxito reproductivo y la reducción del riesgo de extinción. Un único MPG era suficiente para el rescate genético, aparentemente debido a que la tasa de migración efectiva quedaba espectacularmente sobredimensionada durante generaciones, cuando el tamaño de la población era pequeño. Un análisis de cuasi-extinción sugiere que las poblaciones replicadas durante el tratamiento 1-MPG se beneficiaron de un saneamiento inicial por la disminución de la endogamia. Aparentemente, las poblaciones de este tratamiento se comportaron tan bien debido a que recibieron el doble beneficio del saneamiento seguido de la inyección genética. Nuestros resultados sugieren la necesidad de posteriores evaluaciones del rescate genético mediante esquemas alternativos. Palabras clave: Riesgo de extinción, Acontecimientos de hundimiento, Rescate genético, Endogamia

Minimizing extinction risk through genetic rescue

According to the genetic rescue hypothesis, immigrants can improve population persistence through their genetic contribution alone. We investigate the potential for such rescue using small, inbred laboratory populations of the bean beetle (Callosobruchus maculatus). We ask how many migrants per generation (MPG) are needed to minimize the genetic component of extinction risk. During Phase 1, population size was made to fluctuate between 6 and 60 (for 10 generations). During this phase, we manipulated the number of MPG, replacing 0, 1, 3, or 5 females every generation with immigrant females. During Phase 2, we simply set an upper limit on population size (.10). Compared with the 0-MPG treatment, the other treatments were equivalently effective at improving reproductive success and reducing extinction risk. A single MPG was sufficient for genetic rescue, apparently because effective migration rate was inflated dramatically during generations when population size was small. An analysis of quasi-extinction suggests that replicate populations in the 1-MPG treatment benefited from initial purging of inbreeding depression. Populations in this treatment performed so well apparently because they received the dual benefit of purging followed by genetic infusion. Our results suggest the need for further evaluation of alternative schemes for genetic rescue