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.