Co-occurring species are rarely considered as a factor infl uencing habitat selection. However, niche theory predicts that sharing resources, predators, and other interspecifi c interactions can limit the environmental conditions under which a species may exist. How does the spatial distribution of one species aff ect that of another within shared landscapes? We tested whether sympatric marten Martes americana and fi shers M. pennanti in a mountain landscape in Alberta, Canada exhibit local-scale spatial segregation, beyond diff erential habitat selection. We modelled marten and fi sher distribution in relation to remotely-sensed habitat data and species co-occurrence, using generalized linear models and informationtheoretic model selection. Marten and fi shers selected diff erent habitat types and showed diff erent responses to habitat fragmentation. Even after accounting for these diff erences, the absence of one species signifi cantly explained the occurrence of the other. We conclude that the spatial distribution of marten and fi shers infl uences habitat selection by each other at landscape scales, and hypothesize that this pattern may result from competition in a spatially heterogeneous environment. Species-habitat models that consider only resources may fail to capture key predictors of species ' occurrence. Reliable prediction and inference requires that ecologists expand from landscapes to also include species-scapes: a spatial plane of species interactions that combines with resources to drive species ' distributions.

Detecting ecological change in mammalian communities requires large volumes of data collected across large landscapes. Noninvasive genetic tagging (NGT) can provide such data and is a common method of estimating species occupancy, distribution, and abundance. Methods to correct errors in genetic analysis exist, but estimating and accounting for detection error in NGT studies—specifically, detection error during hair trapping—has received less attention. If detectability varies with an ecological characteristic that is instead attributed to occupancy, detection error may lead to spurious conclusions. We demonstrate how multi‐method occupancy models informed by camera‐trapping data can quantify error, partition sources of variability, and estimate occupancy from NGT studies. We surveyed marten (Martes americana), fisher (Pekania pennanti), and wolverine (Gulo gulo) occurrence via hair trapping and camera trapping for 3 repeated monthly surveys at 66 sites in the Rocky Mountains of Alberta, Canada. Camera traps photographed the hair traps and surrounding sampling site. We used multi‐method occupancy models to estimate site occupancy, probability of detection, and conditional occupancy at a hair trap. We tested the predictions that detection error in NGT studies could be induced by temporal variability and behavioral variability arising from the presence of heterospecifics. Models indicated that NGT via hair trapping consistently underestimated occupancy of marten, fisher, and wolverine compared to cameras. The magnitude of bias varied, but at worst underestimated occupancy by half. The presence of a heterospecific affected a species' detection at hair traps. Wolverine presence increased marten detection, whereas marten decreased fisher detection at NGT traps. For all species, detection error was reduced through successive monthly surveys, although heterogeneity induced by other mustelids remained. Detection error from multiple sources can bias NGT occupancy estimates, with implications for population estimation, ecological inference, species' legal status assessments, and conservation decisions. We recommend that NGT studies quantify and correct for detection error using independent survey methods and multi‐method occupancy models, to improve the ability to answer ecological questions and make conservation decisions in the face of ecological change. © 2014 The Wildlife Society.

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The influence of residual tree patch size after harvest on understorey plant communities was investigated in aspen and pine – black spruce forests in boreal Alberta, Canada. Three different patch size treatments were created in both study areas; patches amounted to 3% residual merchantable timber in each cutblock. In the aspen study area, species richness was higher in cutover matrix than in preharvest forests and large residual patches. Species richness was larger in small residual patches and the cutovers than in the preharvest forests. In contrast, in pine – black spruce stands, species richness did not differ between the preharvest forests, the large and small residual patches, and the cutover matrix; however, lower richness was observed in medium-sized residual patches than in the cutover matrix. In both study areas, significant differences between understorey plant communities in the preharvest forests and those in large, medium-sized, and small residual patches were observed. In addition, large and medium-sized residual patches had understorey plant communities that differed from those in the cutover matrix. If forest managers expect to maintain preharvest understorey plant communities within cutblock boundaries, residual patches need to be larger than those tested.

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