Do soil born microorganisms shape preferences of invertebrate predators for seeds from soil bank?

Plants are colonized by microorganisms, which support their growth, productivity, utilization of nutrients, production of secondary metabolites and also suppress pathogens or protect plants from herbivores. In our work we focused on interactions between bacteria associated with seeds in a soil seed bank and consumption of those seeds by carabid beetles. Specifically, we tested how the structure of bacterial community and its changing over two year’s burial in soil influences seed consumption. Seeds of seven plant species differing in size and shape but with known palatability to carabid beetles were used in the experiment conducted at one ruderal site. Bacterial diversity increased significantly after burial of all seed species but remained similar in the second year. It was possible to distinguish three types of seeds with respect to changes of bacterial community composition: 1) Remained unchanged over the two years burial, 2) Changed in the first year after burial and then remained the same. 3) Changed gradually over the two years. In most species the diversity of microbial communities did not or only very loosely correlated with change in viability or seed mass. The only exception was P. lanceolata, for which both the viability and relative mass strongly negatively correlated with microbial diversity. In a simple model the overall mass consumption but not the total consumption was reduced by increased bacterial diversity, but in the more complex model, which included also seed species and interactions this effect was overpowered by the effect of differences between the individual seed species.