Artículo de publicación ISIA high proportion of plant species is predicted to be threatened with extinction in the near future. However, the threat status of only a small number has been evaluated compared with key animal groups, rendering the magnitude and nature of the risks plants face unclear. Here we report the results of a global species assessment for the largest plant taxon evaluated to date under the International Union for Conservation of Nature (IUCN) Red List Categories and Criteria, the iconic Cactaceae (cacti). We show that cacti are among the most threatened taxonomic groups assessed to date, with 31% of the 1,478 evaluated species threatened, demonstrating the high anthropogenic pressures on biodiversity in arid lands. The distribution of threatened species and the predominant threatening processes and drivers are different to those described for other taxa. The most significant threat processes comprise land conversion to agriculture and aquaculture, collection as biological resources, and residential and commercial development. The dominant drivers of extinction risk are the unscrupulous collection of live plants and seeds for horticultural trade and private ornamental collections, smallholder livestock ranching and smallholder annual agriculture. Our findings demonstrate that global species assessments are readily achievable for major groups of plants with relatively moderate resources, and highlight different conservation priorities and actions to those derived from species assessments of key animal groupsConsejo Nacional de Ciencia y Tecnologia 000000000011820

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a b s t r a c tGuanaco populations face different feeding constraints along their altitudinal migrations in Andean mountains. The guanaco's diet and food availability were analyzed using microhistological analysis and point-quadrat transects at four sampling sites from the summer range, and four sites from the winter range of a High Andean migratory population. Significant differences were detected with Kruskal-Wallis ANOVA, feeding selection by the 2 test, and dietary preferences by Bailey's confidence interval. Summer range was characterized by having higher plant diversity with more availability of grass-likes (Ciperaceae and Juncaceae) and forbs, compared to winter range. Sites with vegas (moist areas associated to streams and ponds, with dense hydrophytic vegetation) showed higher plant cover and diversity, also diet diversity was higher. Diet was dominated by grass-likes and grasses at sites with wetlands, only by grasses at the other sites, especially in winter. The highest diet-availability similarity occurred in the vega microhabitat, but species from slopes were also eaten at sites with wetlands. Grasses were preferred and shrubs were avoided in both seasonal ranges. The narrower guanaco's diet in winter, and the higher dietary diversity where plant cover and diversity are higher, both agree with the hypothesis of selective quality. A summer opportunistic feeding behavior shifts to a more selective behavior during winter. Winter browsing barely occurred, and grasses prevailed in the diet of both seasons. Altitudinal migration, forced by the deep snow, could favor guanacos to maintain a grazer strategy year round. Vegas and grasslands, in the summer and winter ranges, have a high feeding relevance for this guanaco population, and connectivity between both ranges is essential for their survival.

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