| Summary: | Aim : Understanding which factors shape and maintain biodiversity is essential to understand how ecosystems respond to crises. Biodiversity in ecological communities is a result of the interaction of various factors which can be classified as neutral or niche-based. The importance of these processes has been debated, but many scientists believe that both processes are important. Here we examined the importance of neutral vs. niche-based factors for shaping invertebrate communities. We hypothesized that if neutral processes are the main drivers of community structure we would not see any clear relationship between the structure of community and ecological factors. If niche-based processes are important we should see clear relationships between community structure and variation in ecological variables. Location : Groundwater-filled lava caves near Lake Mývatn, Iceland. Methods : We collected various ecological variables from these caves. Invertebrate communities were collected on the hard bottom using stone scrubbing and from epibenthic traps. Results: Both communities were species-poor, with low densities of invertebrates, showing the resource-limited and oligotrophic nature of these systems. Unusually for Icelandic freshwater ecosystems, the benthic communities were not dominated by Chironomidae (Diptera) larvae, but rather by crustaceans, mainly Cladocera. The epibenthic communities were not shaped by environmental variables, suggesting that they may be structured primarily by neutral processes. The benthic communities were shaped by the availability of energy, and to some extent pH, suggesting that niche-based processes were important drivers of community structure, although neutral processes may still be relevant. Main conclusions : The results suggest that both processes are important for invertebrate communities in freshwater, and research should focus on understanding both of these processes. The ponds we studied are representative of a number of freshwater ecosystems that are extremely vulnerable to human ...
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