Interactions and associations in a Jurassic geothermal landscape from Patagonia, Argentina

GARCIA MASSINI J.L.; SAGASTI A.J.; ESCAPA I.E.; D. M. GUIDO

Salvador

Congreso; XIV International Palynological Congress X International Organisation of Palaeobotany Conference; 2016

International Organization of Paleobotany, International Federation of Palynological Societies, Asociacion Latinoamericana de Paleobotanica y Palinologia

Herein, we describe diverse examples of interactions and associations between plants, fungi, bacteria, animals and protists in a Jurassic geothermal landscape in southern Patagonia (Santa Cruz, Argentina). Fossils are preserved as silicifications in cherts deposited in La Matilde and Chon-Aike formations of the Bahia Laura Group in north-central Santa Cruz, Patagonia, Argentina. Interactions include parasitism represented by fungus-infected plant organs, and pollen and spores showing a variety of host reaction responses. The presence of galls and other decay scars in a wood specimen infected with actinomycetes and fungi also reveals parasitic interactions. Mutualism has also been recorded, being characterized by young plant roots infected by arbuscule-forming fungi. Various other interactions are recorded as diverse decay patterns left by fungal decomposers and xylophagous insects on wood. Interactions are also deduced from the contents of a diversity of coprolites present, which indicate a range of animals specializing in single components and others on a variety of elements. Associations include different forms of epiphytism by fungi, cyanobacteria and protists on plant stems. Furthermore, associated with cyanobacteria filaments are epiphytic algae that occur tightly packed at their bases. Altogether, this new survey of the interactions and associations provides an unusually rich source of information about ecological dynamics in a Jurassic landscape. Represented are a range of roles for fungal, animal, plant, bacteria and protist components of the community comparable to those developed by extant counterparts in modern environments. In addition, it shows that formation of endomycorrhizae probably was a common form of coping with unusually extreme parameters in the geothermal systems. Our survey also suggests that a number of animals occupied different trophic positions in the community, mutually influencing one another by acting as specific and generalist consumers. It also shows that the associations between different biotic components responded to mutual influences triggered by living in the same environment (or niche superposition) or to more specifically driven mechanisms, in ways that affected all parts involved. This report provides a promising starting point for the reconstruction of the structure and functions of the Jurassic geothermal landscapes in Patagonia. As such, it represents a unique window into the past about biotic interactions and associations in Jurassic terrestrial ecosystems.