Actinedid mite community diversity in a succession gradient in continental sand-dune habitats of central Europe

The actenidid mite communities were studied across a small-scale successional gradient in continental sandy habitats in southwest Germany. Nine sites ranging from open sands to woodlands were sampled between 1993 and 1996. Along the gradient, increasing vegetation corresponded significantly with increasing soil eutrophication. Species-poor communities with strong eudominances of single species occurred in the open sands. Parallel to increasing successional status, actenidid densities and species richness increased and dominances shifted strongly, with balanced dominance structures in the most developed sites. Specialized, psammophilous species were mostly limited to the open sands and short-grass sites. Eurytopic species were often limited to and dominant in the more highly eutrophied sites. Many psammophilous taxa are distributed world-wide but extremely disjunctly, occurring only in nutrient-poor, abiotically extreme psammic habitats.