Heterotroph species extinction, abundance and biomass dynamics in an experimentally fragmented microecosystem

1. Species extinction in fragmented habitats is a non-random process described by transient, rather than equilibrium dynamics. Therefore, 'static' approaches focusing on experimentally established spatial gradients of diversity may fail to capture essential aspects of ecosystem responses to species loss. 2. Here we document temporal changes in microarthropod species abundance, biomass and richness during a community disassembly trajectory following experimental habitat fragmentation of a moss-based microecosystem. 3. Habitat fragmentation reduced heterotrophic species richness and community biomass in remnant moss fragments. Extinction was biased towards rare species, and thus occurred initially without significant changes in total community abundance and biomass. Eventual reductions in abundance and biomass were found to lag behind observed declines in species richness. 4. The presence of moss-habitat corridors connecting fragments to a large 'mainland' area coupled with an immigration rescue effect maintained microarthropod richness, abundance and biomass within remnant fragments. 5. Our results indicate that both the order of species loss and the dynamics of remnant populations influence the magnitude and timing of ecosystem-level responses to habitat destruction and isolation.