Fungal-arthropod-plant interactions from the Jurassic petrified forest Monumento Natural Bosques Petrificados, Patagonia, Argentina

Abstract

Fungal-arthropod-plant interactions are described from the Middle Jurassic Monumento Natural Bosques Petrificados, Santa Cruz, Patagonia, Argentina. Fossils consist of a silicified araucarian log that appears differentially decayed and displays galleries bored in patterns resembling those produced by extant wood-boring beetles. Galleries are filled completely with frass that is reworked into smaller galleries containing spherical to ellipsoidal coprolites. The coprolites are of possible mite origin and contain fungal and plant remains. Fungi are also found growing from the walls of the smaller galleries and from the coprolites. Identifiable fungal propagules include asexual structures typical of extant imperfect fungi. Comparison with modern wood with similar patterns suggests a xilophagous role for the wood borer, whereas the smaller galleries and coprolites likely are products of a smaller xylophagous/fungivorous woodborer. Decay patterns in the silicified woods are like those produced by extant saprotrophic and pathogenic wood-rotting fungi in modern ecosystems. The fungus on the walls of the galleries and on the coprolites most likely was saprotrophic. However, additional indirect and direct interactions (i.e., phorisms) similar to those between conifers, mites, beetles, and fungi in modern ecosystems could be hypothesized. This report provides unique direct fossil evidence of multitrophic fungal-arthropod-plant interactions and suggests the possibility that complex interactions like those in modern conifers might have been in place by at least the Jurassic. These results underscore the importance of fungi as key elements of past ecosystems, acting as drivers of biological cycles and symbionts with a variety of organisms.