Data from: Putting the waste out: a proposed mechanism for transmission of the mycoparasite Escovopsis between leafcutter ant colonies

The attine ant system is a remarkable example of symbiosis. An antagonistic partner within this system is the fungal parasite <i>Escovopsis, </i>a genus specific to the fungal gardens of the Attini. <i>Escovopsis </i>parasitizes the <i>Leucoagaricus </i>symbiont that leaf-cutting ants (<i>Acromyrmex</i>, <i>Atta</i>) have been farming over the past 8-12 million years. However, it has been a puzzle how <i>Escovopsis </i>reaches its host. During a seasonal survey of nests of <i>Acromyrmex subterraneus subterraneus </i>in Atlantic rainforest in Brazil, <i>Escovopsis </i>was detected in all the sampled fungal garden waste tips or middens (n = 111). Middens were built strategically; always below the nest entrances. Here, we report the first evidence of a putative mechanism for horizontal transmission of <i>Escovopsis </i>between attine colonies. It is posited that leaf-cutting ants pick up the spores from soil and litter during foraging and vector the mycoparasite between attine colonies. Field and laboratory experiments, using <i>Atta laevigata</i> and <i>Acromyrmex subterraneus subterraneus</i>, confirm that <i>Escovopsis </i>spores are phoretic, and have an in-built dormancy, broken by the presence of their <i>Leucoagaricus </i>host. However, in the coevolutionary arms race, <i>Atta </i>ants may lose out – despite most species in the genus investing in a more advanced waste disposal system – due to the insanitary habits of their <i>Acromyrmex</i> neighbours.