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Current land use and climate change are prompting questions about the ability of plants to adapt to such environmental change. Therefore, we experimentally addressed plant performance and quantitative-genetic diversity of the common Alpine Meadow Grass Poa alpina. We asked how land use and altitude affect the occurrence of P. alpina in the field and whether its common-garden performance suggests adaptation to conditions at plant origin and differences in quantitative genetic diversity among plant origins. Among 216 candidate grassland sites of different land use and altitude from 12 villages in the Swiss Alps, P. alpina occurred preferentially in fertilized and grazed sites and at higher elevations. In a common garden at 1,500 m asl, we grew two plants of [600 genotypes representing 78 grassland sites. After 2 years, nearly 90% of all plants had reproduced. In agreement with adaptive advantages of vegetative reproduction at higher altitudes, only 23% of reproductive plants from lower altitudes reproduced via vegetative bulbils, but 55% of plants from higher altitudes. In agreement with adaptive advantages of reproduction in grazed sites, allocation to reproductive biomass was higher in plants from grazed grasslands than from mown ones. For 53 grasslands, we also investigated broad-sense heritability H 2 , which was significant for all studied traits and twice as high for grazed as for mown grasslands. Moreover, possibly associated with their higher landscape diversity, H 2 was higher for sites of villages of Romanic cultural tradition than for those of Germanic and Walser traditions. We suggest promoting diverse land use regimes to conserve not only landscape and plant species diversity, but also adaptive genetic differentiation and heritable genetic variation.

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The diversity of human land use in the Alps was associated with genetic diversity of P. alpina. Therefore, the ongoing socio-economically motivated land-use changes, which reduce the number of different land-use types, will affect the genetic diversity of P. alpina negatively.

The important fodder grass Poa alpina L. occurs at several ploidy levels with common aneuploidy. We isolated and characterized five polymorphic microsatellite markers for the study of molecular genetic variation of this species. As first examples of the value of the developed markers for population genetic analyses, we show that plants with more chromosomes have more microsatellite bands and that isolation by distance plays a small role in shaping microsatellite diversity of P. alpina in the Swiss Alps.

Agriculturally used grasslands in the Alps are characterised by a trade-off between high fodder production in some and high plant species richness in others. In contrast to plant species richness and production, however, little is known on the relevance of biological interactions between plants, invertebrate herbivores, and fungal pathogens for grasslands in the Alps. At the time when the vegetation was fully developed, but prior to agricultural use, we examined whether leaf damage by herbivory and fungal pathogen infection, and their diversity, are affected by plant functional group, land use, and altitude. Moreover, we studied whether extent and diversity of leaf damage are related to each other, to plant species richness, and to standing crop. We recorded the leaf area damaged by ten types of herbivory and five types of fungal pathogen infection on 12,054 plant leaves of legumes, other forbs, and graminoids collected in 215 grassland parcels in 12 valleys in the Swiss Alps. With 83 % of all leaves infested, herbivory and fungal pathogen infection were omnipresent. However, only 2.7 % leaf area was damaged by herbivory and 1.2 % by fungal pathogens. Damage by herbivory was highest on legumes, and damage by fungal pathogens was highest on graminoids. More leaf damage by herbivory occurred in traditionally mown sites and at lower altitudes, while damage by fungal pathogen infection was independent of land use and altitude. Most types of herbivory were found on legumes and on leaves from fertilised sites, whereas the number of fungal pathogen types was highest on graminoids and in unfertilised sites. Larger standing crop was associated with higher leaf damage and diversity of herbivory types per leaf. Neither damage by herbivory nor by fungal pathogens was correlated with plant species diversity. In more plant species rich parcels, the number of herbivory types was lower at the leaf level, but tended to be higher at the parcel level. Our results highlight the omnipresence of plant-herbivore and plant-pathogen interactions. They suggest that current land use changes from mowing to grazing or to abandonment decrease the diversity of herbivory, and that fertilisation decreases pathogen diversity. As our results did not reveal conservation conflicts between diversities of plants, herbivores, and fungal pathogens, and as the damage from herbivory and pathogens is generally low, we conclude that for protecting the high diversity of plant-herbivore and plant-pathogen interactions a diverse low-intensity land use should be maintained.