Sooty molds from the Jurassic of Patagonia, Argentina

NUNES, C.; GARCIA MASSINI, J.; ESCAPA, I.; GUIDO, D.M.; CAMPBELL, K.

AMERICAN JOURNAL OF BOTANY

BOTANICAL SOC AMER INC

Lugar: St. Louis; Año: 2021 vol. 108 p. 1464 - 1482

0002-9122

The sooty molds are an ecological group of ascomycetes with epiphyllous saprotrophic habit. They can reduce the photosynthetic surface of the plants because they form a dense dark coat on the surfaces of leaves, branches and trunks. This group of fungi comprises several taxa that can be phylogenetically distant (i.e. members of the classes Dothideomycetes and Eurotiomycetes). Their fossil record extends more or less continuously back to the early Cretaceous and all the reports were described almost exclusively from amber deposits of the Northern Hemisphere and with just a single report from an amber deposit of the Southern Hemisphere. Here we describe new specimens of saprotrophic epiphyllous ascomycetes, studied from thin sections of chert blocks collected from hot spring deposits of the Bahía Laura Group (Jurassic) in the Deseado Massif from Southern Patagonia, Argentina. The fungi are covering the surface and axils of leafy twigs with podocarpaceous affinities, forming dense subicula comprised by opaque moniliform hyphae. Additionally, several asexual and sexual reproductive structures are observed. Based on the vegetative and reproductive characters three morphological types were identified with different affinities within the order Capnodiales of the class Dothideomycetes. This finding extends the geographic fossil range of the Capnodiales to the South American continent and extends their biocron to the Jurassic. The epiphytic habit of the fungi described here and the absence of reaction structures in the host suggests a saprotrophic nutritional mode, thus the ecological habit of these fungi today dates back to the Jurassic. In particular, the association of these fungi with the Podocarpaceae is now proved to be ancient and dates back to the Jurassic. In addition, this new record provides an additional reference point on the diversity of interactions that characterized Jurassic forested environments related to geothermal systems in Patagonia.