Fig. 1: Different scenarios of temporal changes in arthropod community assembly and biomass between a baseline community and a comparison community.

a–c, Changes in the total community biomass can be associated with changes in species richness (a), species identity (b) and abundance of persisting species (c). The species richness component assumes an equal (average) contribution of all species to community biomass. However, species under turnover may have non-average biomass (b), in which case their identity must be considered. Consequently, the species identity component reflects the difference between the biomass change expected from the species richness component and the actual observed biomass change associated with species turnover. In comparison community a, one species with average total biomass relative to the baseline community was lost (the expected species richness change explains the observed biomass change); in comparison community b, one species with below-average total biomass was lost and one species with even lower biomass was gained (species identity change has to be considered to explain the observed biomass change); and in community c, no species was lost or gained, but the abundances of two species declined (abundance changes of persisting species explain the biomass change). All scenarios can occur in combination (see Extended Data Fig. 1 for an illustrated example). Reversing the roles of baseline and comparison in this hypothetical scenario would illustrate opposite trends of community and biomass changes. Credit: arthropod icons, Gabriele Rada/iDiv.