Abstract

The metacommunity framework has been rarely adopted to investigate the underlying ecological mechanisms shaping microbial communities. With the aid of advanced molecular techniques, we investigated sediment communities of Fungi, Bacteria and Archaea in four Italian show caves aiming to disentangle the effects induced by tourists on species richness and composition from environmental filtering and dispersal driven mechanisms. We modelled community changes against human disturbance ---measured as the distance from the tourist path---demonstrating that the presence of visitors in caves decreases fungal species richness and causes species replacement in Bacteria and Archaea. Environmental filtering affects species richness and composition of Fungi and species richness of Archaea, while a minor role was played by dispersal, influencing only species richness in Fungi. We provide new perspectives on the dynamics of microbial communities under human disturbance suggesting that a proper understanding of the underlying selective mechanisms requires a comprehensive and multi-taxonomic approach.