Discovered in Costa Rica's Corcovado National Park, and later recorded from Panama, this species thrives in lowland tropical coastal rainforests on smooth bark of smaller, often young trees.

The authors suggest that molecular phylogenetic studies are needed to clarify natural relationships in this complex group of mostly tropical taxa.

[2] Arthonia isidiata occurs in lowland tropical coastal rainforests, specifically in Parque Nacional Corcovado in Costa Rica.

It grows frequently on trees with smooth bark in the area, but has not been found in the apparently drier forests south of the field station.

The forest where the type locality of Arthonia isidiata thrives consists of a mixture of sandy and alluvial soils, with a sparse understory and light conditions ranging from moderately exposed to rather shaded.