seed predation, Harpalus affinis, Pseudoophonus rufipes, seed density, selectivity

Post-dispersal seed predation is a phenomenon that reduces the abundance of weed seeds in the soil seedbank. In temperate zones, granivorous and polyphagous ground beetles (Coleoptera: Carabidae) are considered to be important weed seed eaters. Several previous studies show that carabid beetles are selective and that their seed preferences are based mainly on size and taxonomic constraints. The aim of the current study was to show if carabid selectivity also depends on physical seed traits. Our analysis was based on seed preferences of two ground beetles ? Harpalus affinis and Pseudoophonus rufipes. The dataset included 63 ranked plant species and for each we searched for several traits (seed mass, volume, total density and shape) in trait databases. Using a cumulative link model we showed that both carabids tend to prefer seeds of optimal seed mass (0.17 mg/ H. affinis; 1.15 mg/ P. rufipes) and also react to density and shape. P. rufipes prefers denser seeds, in H. affinis we observed opposite pattern. Disc- or needle-like seeds are likely more often eaten then seeds with spherical shape. Preferences of carabid seed predators are thus determined by these traits.

Post-dispersal seed predation is a phenomenon that reduces the abundance of weed seeds in the soil seedbank. In temperate zones, granivorous and polyphagous ground beetles (Coleoptera: Carabidae) are considered to be important weed seed eaters. Several previous studies show that carabid beetles are selective and that their seed preferences are based mainly on size and taxonomic constraints. The aim of the current study was to show if carabid selectivity also depends on physical seed traits. Our analysis was based on seed preferences of two ground beetles ? Harpalus affinis and Pseudoophonus rufipes. The dataset included 63 ranked plant species and for each we searched for several traits (seed mass, volume, total density and shape) in trait databases. Using a cumulative link model we showed that both carabids tend to prefer seeds of optimal seed mass (0.17 mg/ H. affinis; 1.15 mg/ P. rufipes) and also react to density and shape. P. rufipes prefers denser seeds, in H. affinis we observed opposite pattern. Disc- or needle-like seeds are likely more often eaten then seeds with spherical shape. Preferences of carabid seed predators are thus determined by these traits.