Microbiological insights into ecology and taphonomy of prehistoric wetlands.

Abstract

In the course of this dissertation, I present investigations of the microbial constituents of fossil plants preserved at an anatomical level of detail, and detail the results of an ecological survey of root-endogenous fungi within the cosmopolitan emergent macrophyte, Typha. These studies together elucidate processes in the taphonomy of fossil plants. Biostratinomy is addressed through descriptions of saprotrophic communities within the Eocene Princeton Chert mire assemblage, and within a Carboniferous fern which previous studies had suggested contained fossilized actinobacteria. Re-investigation of the ‘actinobacteria’ suggests instead that the structures are disordered ferrous dolomites, raising implications for the contribution of sulfate-reducing bacteria to the early-diagenesis mineralization of plants preserved in carbonaceous concretions. The fossilized remains of saprotrophic and putatively endophytic fungi within roots of in-situ plants from the Princeton Chert also provide insight into early diagenesis. Some of the fungi described herein are preserved in several co-occurring developmental phases, providing evidence that early phases of silicification in this assemblage were rapid. As the Princeton Chert is not a hot-spring sinter deposit, these data conflict with prior hypotheses for the preservation of this peat-forming wetland assemblage. Understanding the microbial paleoecology of this system, and other wetland assemblages that constitute paleobotanical Konservat-lagerstätten, will provide important foundations upon which to improve hypotheses of plant-microbe interactions in the fossil record. Research into fossil plant-microbe interactions must, however, be conducted with reference to appropriate biogeochemical analogues. The concluding component of this dissertation establishes that endogenous fungi in contemporary wetland plant roots are affected by persistent inundation. Although the constituents of root-endogenous communities do not appear to change between inundated roots and those growing in subaerially-exposed soils, their incidence within roots does differ. These data offer clear implications for assessing the probable ecology of in-situ fossil plants that hosted endogenous microbial communities during life.