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The effectiveness of corridors in maintaining dispersal in fragmented landscapes is a question of considerable conservation and ecological importance. We tested the efficacy of corridors as residual landscape structures in maintaining population structure in the red-backed vole ( Clethrionomys gapperi ), a closed-canopy specialist, and the deer mouse ( Peromyscus maniculatus ), a habitat generalist. In coniferous forests managed for timber production in northeastern Washington, we sampled pairs of populations in three landscape classes: (1) contiguous landscapes, in which sites were located completely within a matrix of closed-canopy forest; (2) corridor landscapes, in which sites were connected by a corridor of closed-canopy forest; and (3) isolated landscapes, in which sites were separated from one another by clearcut or young regeneration stands. For each species, we used four microsatellite loci to quantify genetic distance between population pairs. Nei's genetic distance ( D s ) increased from smallest to largest in the order of contiguous, corridor, and isolated landscapes for C. gapperi. For P. maniculatus, genetic distances across landscape configurations were not significantly different. The differences between the two species indicate that they respond differently to the presence of forest corridors. In managed forests, corridors between unlogged habitats appear to maintain higher population connectivity for C. gapperi than landscapes without corridors. Evaluación de la Efectividad de Corredores: Una Estrategia GenéticaResumen: La efectividad de los corredores para mantener la dispersión en paisajes fragmentados es una situación de considerable importancia ecológica y de conservación. Evaluamos la efectividad de los corredores como estructuras residuales del paisaje en el mantenimiento de la estructura poblacional del ratón de campo de dorso café ( Clethrionomys gapperi ), un especialista de dosel cerrado, y del ratón ciervo ( Peromyscus maniculatus ) un generalista de hábitats. Hicimos un muestreo en pares de poblaciones en bosques de coníferas manejados para la producción maderera en tres clases de paisaje de Washington nororiental: (1) contiguo, sitios localizados completamente dentro de una matriz de bosque con dosel cerrado; (2) corredor, sitios conectados por un corredor de bosque con dosel cerrado; y (3) aislado, sitios separados uno del otro por talas o por rodales de regeneración joven. Para cada especie, usamos cuatro loci microsatélite para cuantificar la distancia génica entre pares de poblaciones. Para C. gapperi , las distancias genéticas de Nei ( D s ) se incrementaron en los paisajes en el siguiente orden: contiguo, corredor, y aislado. Para P. maniculatus , las distancias genéticas a lo largo de configuraciones del paisaje no fueron significativamente diferentes. Las diferencias entre estas dos especies indican que responden de diferente manera a la presencia de corredores forestales. En bosques manejados, los corredores entre hábitats sin talar aparentemente mantienen una conectividad ...

Translocation of animals to re-establish extirpated populations or to maintain declining ones has often been carried out without genetic information on source or target populations, or adequate consideration of the potential effects of mixing genetic stocks. We consider the conservation status of the fisher (Martes pennanti) and evaluate the potential genetic consequences of past and future translocations on this medium-sized carnivore by examining population variation in mitochondrial control-region sequences. We sampled populations throughout the fisher's range in North America including five populations unaffected by translocations and two western populations that had received long-distance translocations. Twelve haplotypes showed little sequence divergence. Haplotype frequencies differed significantly among subspecies and between populations within subspecies. Analysis of molecular variance (amova) and neighbour-joining analyses of haplotype relationships revealed population subdivision similar to current subspecies designations, but which may reflect an isolation-by-distance pattern. Populations in Oregon and in Montana and Idaho received several translocations and each showed greater similarity to the populations where translocations originated than to adjacent populations. Additional sequences obtained from museum specimens collected prior to any translocations suggest historical gene flow among populations in British Columbia, Washington, Oregon, and California. Anthropogenic impacts in that region have greatly reduced and isolated extant populations in Oregon and California. Future translocations may be necessary to recover populations in Washington and portions of Oregon and California; our results indicate that British Columbia would be the most appropriate source population.

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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.Abstract. This study considers several questions about interspecific competition and habitat use by desert small mammals. From 1971 through 1973, rodent population data were collected by livetrapping on a creosote bush bajada located near Las Cruces, New Mexico, USA. At each trap station, measurements of the vegetation were taken to provide a description of the microhabitat surrounding each station. Multiple regression analysis was used to estimate the effects of competition and habitat selection in determining the local distributions and abundances of the rodent species in each year. The 10 species form four guilds: (1) Onychomys arenicola, (2) Neotoma albigula and N. micropus, (3) Dipodomys merriami and D. ordii,' and (4) Perognathus intermedius, Pg. penicillatus, Peromyscus eremicus, P. maniculatus, and P. leucopus. None of the competition estimates for between-guild interactions was significantly negative, indicating that a species in one guild did not have any inhibitory effects on species in other guilds. Coexistence of the four guilds was attributable in some cases to differences in food and habitat preferences, and in others to differences in foraging methods related to body size. Competition was not observed within the Dipodomys guild because of the different microhabitat specializations of the two species. The three Peromyscus spp. appear to avoid competition with each other by complementary habitat use; competition was observed within the Perognathus-Peromyscus guild, but only among Perognathus intermedius, Pg. penicillatus, and Peromyscus eremicus. The magnitudes of the observed competitive interactions varied significantly from year to year with changes in both rodent densities and resource availabilities. The competitive relationships within the guild were consistent, however, and the three species were ranked in increasing competitive ability: Perognathus penicillatus < Perognathus intermedius < Peromyscus eremicus. Some evidence suggests that competitive ability increases with increasing habitat specialization.

Abstract:Increasing concerns about global environmental change and food security have focused attention on the need for environmentally sustainable agriculture. This is agriculture that makes efficient use of natural resources and does not degrade the environmental systems that underpin it, or deplete natural capital stocks. We convened a group of 29 'practitioners' and 17 environmental scientists with direct involvement or expertise in the environmental sustainability of agriculture. The practitioners included representatives from UK industry, non-government organizations and government agencies. We collaboratively developed a long list of 264 knowledge needs to help enhance the environmental sustainability of agriculture within the UK or for the UK market. We refined and selected the most important knowledge needs through a three-stage process of voting, discussion and scoring. Scientists and practitioners identified similar priorities. We present the 26 highest priority knowledge needs. Many of them demand integration of knowledge from different disciplines to inform policy and practice. The top five are about sustainability of livestock feed, trade-offs between ecosystem services at farm or landscape scale, phosphorus recycling and metrics to measure sustainability. The outcomes will be used to guide ongoing knowledge exchange work, future science policy and funding.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.