The researchers looked at different types of animals and plants in mountain grasslands in the European Alps to see how species diversity changes with elevation. They studied nine groups including plants, insects, spiders, and worms. By comparing the number of species and how they change from one altitude to another, they found that different groups of species prefer different elevations. Some groups had more species at mid-altitudes, while others had more at higher or lower elevations. The way species changed with altitude was different for each group, with some showing a hump-shaped pattern and others a linear decrease or increase. The study suggests that protecting species and their habitats in mountain areas should consider the entire environment, rather than just focusing on specific locations.