Abstract

Studying biodiversity in extreme environments allows us to understand how individuals and whole ecological communities are able to survive at the limits for life. We characterized plant biodiversity in an altitudinal transect along the western slope of the Andes in the Atacama Desert. Here, plants must overcome aridity, high radiation and nutritional shortage among other extreme conditions. Plant biodiversity in the hyperarid Atacama varies over time in response to fluctuating environmental conditions from inter-annual to decadal timescales. Multiple life habit strategies are utilized in this environment such as annuals, which commonly avoid drought years by forming soil seed banks that germinate when conditions are suitable. To establish the composition of these plant communities we performed plant diversity surveys over seven consecutive years along an altitudinal transect. We observed a total of 71 different plant species with significant inter annual variation (31 to 63 species) and species persistence (years of appearance, from one to seven years). Environmental DNA in surface soil samples complemented the surveys and revealed hidden plant diversity. DNA barcode analysis revealed seven new taxa in the area, but tended to show broad distributions of different plant DNA. To complement field and molecular surveys, we further performed an analysis of soil seed banks using the seedling emergence method. The soil seed bank proxy shows that viable seeds have wider ranges than observed for plant species during surveys (in agreement with the DNA barcode method). Our results show higher than anticipated plant richness and composition along the transect. These wider ranges provide adaptive flexibility at the community level to changes in climate in Atacama Desert.