Ant handling changes myrmecochore seed coat microbiomes and alters diversity of seed-borne plant pathogenic fungi

The putative benefits to seeds in myrmecochory (ant-mediated seed dispersal) are often cast in a reward context. However, microbes have been mostly overlooked as seed mortality agents in myrmecochory, as have potential treatments provided by ant-handling. We investigated the effects of ant handling on the diversity of seed coat fungal communities of three myrmecochorous plant species. Ant-handling altered measures of both alpha and beta diversity of fungal communities. Ant-handled seeds harbored different overall fungal communities and plant pathogen communities than non-ant-handled seeds. The myrmecochore pathogenic fungal community showed high dissimilarity (high pairwise community turnover) between ant-handled and control seeds, while beta diversity measures for ant-handled seeds and seeds with manually-removed elaiosomes were less dissimilar. Ant handling may offer an additional benefit to myrmecochorous seeds via the reduction of the seed coat pathogenic community, which may be driven by elaiosome removal or as a byproduct of ant cleaning behaviors and chemical secretions.