Abstract
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 disturbance,
making it even more important to understand how their biodiversity is
shaped and maintained.