Harper , Carla J , Taylor, Thomas N , Krings, Michael , Taylor, Edith L .
Foliar fossil fungi: Leaf–fungal interactions from the Permian and Triassic of Antarctica.
Leaves constitute a harsh environment for fungi due to a variety of abiotic and biotic factors, e.g., temporary nutrient availability, extreme fluctuations in humidity, temperature, gas exchange gradients, and ultraviolet radiation. Despite these factors, leaf endophytes and epiphytes represent a major component of extant fungal diversity. The difficulty in studying epiphyllous fungi in the fossil record is that the fine microdetail of the fungus, i.e., sexual, asexual, and vegetative remains needed for taxonomic assignment, are often not preserved or lost through investigative techniques. To date there is little evidence of permineralized pre-Cretaceous fungal endophytes and epiphytes on or within leaves. In this contribution we expand the evidence of Paleozoic and Mesozoic permineralized leaf fungi with examples from the Permian and Triassic of Antarctica. In combination with thin sections and focal stacking software we are able to document and hypothesize several different types of fungus-leaf interactions. In Antarctic Permian peats Glossopteris leaves are the dominant plant fossil and provide ample evidence of leaf-colonizing fungi. Fungi associated with Glossopteris leaves include ramifying hyphae within mesophyll and vascular tissues of varying diameter, as well as dense mycelia between individual leaves in leaf mats. Additional evidence includes various types of fungal reproductive units of unknown affinity. These structures possess a mycelial network encasing a central spore, and may represent a gleba or a hyphal mantle (Glomeromycota and zygomycetes species). This evidence suggests that fungi played a major role in the decomposition of Glossopteris leaf mats or interacted (e.g., endophytic or epiphytic) with the leaves while they were still attached. In contrast to the Permian, Triassic leaf mats are more diverse, e.g., Dicroidium (seed fern), marattialean fern pinnules, Heidiphyllum (voltzialean conifer) leaf types, and show examples of fungi interacting with leaves. These fungal endophytes produce moniliform hyphae in mesophyll cells directly below the epidermis and extend intracellularly to adjacent cells. In the Triassic leaf mats are multiple specimens of Endochaetophora sp., a fungus that is considered a type of zygomycete. The consistent association of Endochaetophora with leaves may suggest its role in decomposing Triassic leaf mats. Although the systematic affinities of many of these fungi currently remain unknown, it is important to document these occurrences in order to increase our understanding of the roles fungi played in late Paleozoic and Mesozoic ecosystems.
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1 - University Of Kansas, Ecology And Evolutionary Biology, 2041 Haworth Hall, 1200 Sunnyside Avenue, Lawrence, KS, 66045, USA
2 - University Of Kansas, Department Of Ecology And Evolutionary Biology, 1200 Sunnyside Avenue, Haworth Hall, Lawrence, KS, 66045-2106, USA
3 - Bayerische Staatssammlung Für Paläontologie Und Ge, Richard-Wagner Strasse 10, Munich, N/A, D-80333, Germany
4 - University Of Kansas, Department Of Ecology And Evolutionary Biology, 1200 Sunnyside Avenue, Haworth Hall, Lawrence, KS, 66045-7600, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Monday, July 28th, 2014
Time: 8:45 AM
Candidate for Awards:Isabel Cookson Award,Maynard F. Moseley Award