Limited persistence of endophytic fungi in leaf-cutting ant gardens

Abstract

Fungi that are known foliar endophytes have often been isolated from leaf-cutting ant fungal gardens. Recent in vitro growth trials showed that endophytic fungal growth was suppressed by the Lepiotaceous fungi cultivated by leaf-cutting ants. Here we conducted experiments with laboratory ant colonies to assess how long one strain of a common endophytic fungus persisted in the ants' fungal garden after incorporation by worker ants. We observed that after 72 hours our focal strain could no longer be cultured from the incorporated leaf material or surrounding garden tissues. Moreover, we were unable to culture our focal strain from the ants' garbage dumps. The limited persistence of an endophyte in ant fungal gardens may be due to ant hygiene behaviors and/or antagonism from the ants' fungal cultivar.

Fungal-Fungal Interactions in Leaf-Cutting Ant Agriculture

“…The differential behavior of the ants toward leaf tissue with or without endophytes, however, suggests that the endophytes are antagonistic to the fungal symbiont of the ants. Furthermore, the ant cultivar must outcompete or detoxify the endophytes that are not removed by the workers [10,101]. In vitro experiments of fungal-fungal interactions suggested that endophytes were inhibited by the ant fungal cultivar [99] implying that both the ants and their cultivar respond to endophytes.…”

Endophytic fungi increase the processing rate of leaves by leaf‐cutting ants (Atta)

“…Both worker ants and their fungal cultivar interact with many bacteria and microfungi during the leaf‐harvesting and gardening process. In particular, several previous studies have isolated strains living inside of the ants' fungal garden that are also known to be fungal endophytes (Fisher et al , 1996; Rodrigues et al , 2008; Urriola et al , 2011). Fungal endophytes live within above‐ground plant parts without causing signs of disease (Wilson, 1995).…”