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 ...

Mech, S. G. and Zollner, P. A. 2002. Using body size to predict perceptual range. -Oikos 98: 47 -52.We examined the relationship between body size and perceptual range (the distance at which an animal can perceive landscape elements) for a group of forest-dwelling rodents. We used previously published data on orientation ability at various distances for three sciurid species (gray squirrel, fox squirrel and chipmunk) and one murid species (white-footed mouse) to build a predictive model. We found a significant positive relationship between perceptual range and body mass. Although this model was built using a 15.5 m high horizon, we used this relation to predict the perceptual range of root voles (3.9-4.3 m) orienting towards a 0.5 m high horizon which was consistent with other empirical work suggesting a value of something less than 5 m. This model illustrates a relationship between perceptual range and body size and can be used to develop starting points for future investigations of perceptual range for similar organisms.

Distinguishing whether pathogens are novel or endemic is critical for controlling emerging infectious diseases, an increasing threat to wildlife and human health. To test the endemic vs. novel pathogen hypothesis, we present a unique analysis of intraspecific host-pathogen phylogenetic concordance of tiger salamanders and an emerging Ranavirus throughout Western North America. There is significant non-concordance of host and virus gene trees, suggesting pathogen novelty. However, non-concordance has likely resulted from virus introductions by human movement of infected salamanders. When human-associated viral introductions are excluded, host and virus gene trees are identical, strongly supporting coevolution and endemism. A laboratory experiment showed an introduced virus strain is significantly more virulent than endemic strains, likely due to artificial selection for high virulence. Thus, our analysis of intraspecific phylogenetic concordance revealed that human introduction of viruses is the mechanism underlying tree non-concordance and possibly disease emergence via artificial selection.

We conducted three experiments with females in different stages of reproductive condition to test alternative hypotheses for the function of scent marking in female prairie voles, Microtus ochrogaster. The three reproductive categories were isolated females prior to sexual stimulation (anoestrous), sexually stimulated (oestrous) and lactating. Females in different reproductive condition were given the opportunity to scent mark clean unmarked substrate or areas that had previously been marked by adult females or adult males. The numbers of scent marks deposited by females did not differ statistically for females in different reproductive condition. However, there was a trend for anoestrous females to mark the most, oestrous females less, and lactating females the least. The lack of scent marking by lactating females might be to reduce conspicuousness to conspecifics or predators. Oestrous females tended to mark the most in the area marked previously by males, although the difference was not statistically significant. Our results provide some support for a mate‐attraction hypothesis and a territorial‐defense hypothesis, but were most consistent with a self‐advertisement hypothesis. Over marking was uncommon and did not differ by experiment or sex of previous donor. Our results suggest that the number and placement of scent marks by females are highly variable and function primarily to convey individual identity.