Biodiversity of soil microarthropods: The filtering of species

Decline of soil microarthropod biodiversity is described in the sequence: old forest stands, low-input grasslands, high-input grasslands (with and without the use of persistent pesticides). With this expected trend of declining biodiversity, the patterns of species losses are analysed with the use of classifications of life-history tactics, feeding guilds and tolerances to drought. Species intolerant to drought are absent in grasslands, but present in old forest stands. Also the fraction of thelytokously reproducing microarthropods is higher in old forest stands compared with low-input grasslands. The main difference between low-input and high-input grasslands is found in the feeding guild structure of the community. Low-input grasslands are dominated by (herbo-) fungivorous grazers, whereas high-input grasslands are dominated by fungivorous browsers. Application of DDT in high-input grasslands shows a high density of microarthropods with a high fraction of thelytokous reproduction, associated with a decrease in genetic variation in a thelytokously reproducing species. Patterns in species losses, the species filters, are explained and discussed. It is shown that the decline of biodiversity is not a random loss of species but follows an identifiable pattern.