For herbivores, nutrient intake is limited by the relatively low nutritional quality of plants and high concentrations of potentially toxic defensive compounds (plant secondary metabolites, PSMs) produced by many plants. In response to phytochemical challenges, some herbivores selectively forage on plants with higher nutrient and lower PSM concentrations relative to other plants. Pygmy rabbits (Brachylagus idahoensis) are dietary specialists that feed on sagebrush (Artemisia spp.) and forage on specific plants more than others within a foraging patch. We predicted that the plants with evidence of heavy foraging (browsed plants) would be of higher dietary quality than plants that were not browsed (unbrowsed). We used model selection to determine which phytochemical variables best explained the difference between browsed and unbrowsed plants. Higher crude protein increased the odds that plants would be browsed by pygmy rabbits and the opposite was the case for certain PSMs. Additionally, because pygmy rabbits can occupy foraging patches (burrows) for consecutive years, their browsing may influence the nutritional and PSM constituents of plants at the burrows. In a post hoc analysis, we did not find a significant relationship between phytochemical concentrations, browse status and burrow occupancy length. We concluded that pygmy rabbits use nutritional and chemical cues while making foraging decisions.

Plant populations are often spatially structured owing to limited dispersal of pollen and seed. Mating between neighboring individuals in such populations often leads to reduced reproductive performance relative to matings between distant individuals. This response, which may be a result of inbreeding depression or prezygotic mating barriers, was investigated for slickspot peppergrass, Lepidium papilliferum L. (Brassicaceae), a rare insect-pollinated mustard endemic to sagebrush-steppe habitat in southwestern Idaho. Through hand pollination experiments we found that individual plants receiving pollen from distant sources (75-100 m and 6.5-20 km away) had significantly higher percent fruit sets than those relying on pollen from neighboring plants (<1 m away). Self pollinated plants produced little or no fruit. These results suggest that L. papilliferum relies primarily, if not exclusively, on outcrossed pollination, and that its populations are spatially structured. Conservation efforts should therefore strive to protect sufficiently large areas of suitable habitat to ensure maintenance of genetic diversity and preserve or enhance connectivity between populations.Key words: Brassicaceae, inbreeding, outbreeding, population spatial structure, rare species.Résumé : A structure spatiale des populations végétales est souvent liée a une dispersion limitée du pollen et des graines. Dans de telles populations, le croisement entre individus contigus conduit souvent à des performances de reproduction réduites, comparativement à celles qui proviennent des croisements entre individus éloignés. Cette réaction pourrait résulter d'une faiblesse de consanguinité ou de barrières pré-zygotiques; les auteurs ont étudié cette question chez la lépidie papillée (Lepidium papilliferum L., Brassicaceae), une espèce rare de moutarde, endémique aux habitats de steppe à armoise du sud-ouest de l'Idaho. Suite à des pollinisations manuelles, les auteurs ont trouvé que les plantes individuelles recevant du pollen de sources distantes (éloignées de 75-100 m et 6,5-20 km), montrent un pourcentage de mise à fruit significativement plus élevé, comparativement à celles qui dépendent du pollen des plantes voisines (<1 m). Les plantes auto-fécondées produisent peu ou pas de fruits. Ces résultats suggèrent que le L. papilliferum s'appuie surtout, sinon exclusivement, sur la pollinisation extérieure, et que sa population est spatialement structurée. Les efforts de conservation devraient chercher à protéger des aires suffisamment vastes d'habitat approprié pour garantir le maintien de la diversité génétique, et assurer ou promouvoir la connectivité entre les populations.

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Sagebrush (Artemisia spp.) habitat in the Intermountain West is one of the most endangered ecosystems in North America due, in part, to fire, climate change, and anthropogenic disturbances. However, restoration efforts rarely consider the dietary quality of sagebrush that is conserved or restored despite growing evidence that it is an influential parameter explaining habitat use by many important wild and domestic herbivores. The objective of this study was to evaluate the capacity of near-infrared reflectance spectroscopy (NIRS) to measure and monitor the dietary quality of sagebrush. Leaf samples were collected from two sagebrush species over two seasons and three sites in Idaho, USA. We developed calibration equations for crude protein (CP), dry matter digestibility (DMD), 1,8-cineole (cineole), and total polyphenolics. The coefficient of determination (r 2) and ratio of performance to deviation (RPD) were 0.93 and 3.5 for CP, 0.83 and 1.8 for DMD, 0.64 and 1.5 for cineole, and 0.64 and 1.6 for total polyphenolics. These results indicate that NIRS may offer a rapid, noninvasive, diagnostic tool for assessing dietary quality of sagebrush, but future research should explore the potential for development of improved prediction equations and in situ analysis of sagebrush dietary quality with field spectroscopy.

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