High-alpine ecosystems are commonly assumed to be particularly endangered by climate warming. Recent research, however, suggests that the heterogeneous topography of alpine landscapes provide microclimatic niches for alpine plants (i.e. soil temperatures that support the establishment and reproduction of species). Whether the microclimatic heterogeneity also affects diversity or species interactions on higher trophic levels remains unknown. Here we show that variation in mean seasonal soil temperature within an alpine pasture is within the same range as in plots differing in nearly 500 m in elevation. This pronounced heterogeneity of soil temperature among plots affected the spatial distribution of flowering plant species in our study area with a higher plant richness and cover in warmer plots. This increased plant productivity in warmer plots positively affected richness of flower visitor taxa as well as interaction frequency. Additionally, flower-visitor networks were more generalized in plots with higher plant cover. These results suggest that soil temperature directly affects plant diversity and productivity and indirectly affects network stability. The strong effect of heterogeneous soil temperature on plant communities and their interaction partners may also mitigate climate warming impacts by enabling plants to track their suitable temperature niches within a confined area.Alpine ecosystems are particularly sensitive to climate change as scenarios predict severe warming for high elevations in alpine regions 1 . Therefore, cold adapted alpine plant species are threatened by increased temperatures 2,3 . Recently, considerable work has described and tested possible scenarios for responses of alpine plants to climate change 4,5 . Regional plant diversity in alpine habitats is expected to change as a result of climate warming due to shifts in temperature niches and species' distributions, which may result in increased competition due to shifts of plants' distributions to higher elevations and consequently the assembly of new communities 6-8 . Plant species richness and composition affects organisms and processes across trophic levels 9 . For instance, the diversities of plants and their flower visitors have been shown to be particularly related due to insect-specific preferences for certain plant species 10-12 . Therefore, a change in plant abundance and distribution and shifts in phenologies due to rising temperatures potentially have negative effects on other trophic levels, in particular on flower visiting insects 13,14 and thus impact community structure and put ecosystem functions at risk 15 .Among the main drivers of (alpine) plant diversity are climatic conditions and biotic interactions [16][17][18][19] . However, plant community composition and diversity are not only shaped by average environmental and climatic conditions but also by local micro-abiotic filtering 20 . Specifically, soil temperatures, which in contrast to air temperatures are strongly shaped by the local topography and intake of solar r...

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Our results do not support the idea of chronic, widespread pollen limitation in the subnival but rather fit into the concept of parental optimism by overinvesting in the number of ovules as an adaptation to variable resource availability.

Understanding the causes and consequences of coexistence and thus biodiversity is one of the most fundamental endeavors of ecology, which has been addressed by studying species’ requirements and impacts – conceptualized as their Grinnellian and Eltonian niches. However, different niche types have been mostly studied in isolation and thus potential covariation between them remains unknown. Here we quantified the realized Grinnellian niche (environmental requirements), the fundamental (morphological phenotype) and realized Eltonian niche (role in networks) of plant and pollinator taxa at a local and regional scale to investigate the interconnectedness of these niche types. We found a strong and scale-independent co-variation of niche types suggesting that taxa specialized in environmental factors are also specialized in their position in trait spaces and their role in bipartite networks. The integration of niche types thus will help to detect the true causes for species distributions, interaction networks, as well as the taxonomic and functional diversity of communities.

High-alpine ecosystems are commonly assumed to be particularly endangered by climate warming. Recent research, however, suggests that the heterogeneous topography of alpine landscapes provide microclimatic niches for alpine plants, which may buffer negative effects.Whether the microclimatic heterogeneity also affects higher trophic levels remains unknown.This study shows that the variation in mean seasonal soil temperature within a single alpine pasture is within the same range as in plots differing in nearly 500 m in elevation. This pronounced heterogeneity affected the spatial distribution of plant cover, richness of flowering plant species and plant species composition. These microclimatic effects on plant communities also affected richness of flower visiting insects and the frequency and structure of plant-insect interactions suggesting an effect of microclimate also on higher trophic levels.Our results may stimulate a re-evaluation of the consequences of climate warming on ecosystems that may compensate warming by microclimatic refuges.