科研之友
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摘要
Premise of research.Although molecular analyses indicate that fungi likely began to diversify in the Proterozoic, fossil remains from this period have not been confidently linked to modern fungal lineages. Less ambiguous Early Paleozoic remains have been attributed to diverse modern fungal lineages, though some classifications have been questioned, and linking fragmentary fossils to modern fungal groups has generally been challenging. Better knowledge of fungal structures most likely to be preserved in the fossil record would aid classifying enigmatic remains. To achieve this, we tested a spectrum of modern fungi that have been linked to Paleozoic fossils and/or display environmental persistence for retention of diagnostic structural features after acetolysis, a high-temperature acid hydrolysis process employed as a proxy for harsh diagenetic processes. Methodology.Standard acetolysis was applied to cultures of blastocladialean, mucoralean, or ascomycete fungi having melanized structures hypothesized to resist hydrolytic degradation; glomalean fungi associated with greenhouse-grown and field-collected thalloid liverworts; and basidiocarp samples from two species of the woody basidiomycete Ganoderma. Pivotal results.Distinctive acetolysis-resistant fungal structures included Allomyces javanicus-resistant sporangia; glomalean hyphae and spores; tubular sporangiophores, globular asexual sporangia, zygosporangia with suspensors, and hyphal tangles of Phycomyces blakesleeanus (Mucoromycotina); conidiophores, phialides, chains of conidia, and cleistothecial walls of Aspergillus chevalieri (Ascomycota); and dense-walled septate hyphae and perithecia of Sordaria fimicola and Chaetomium globosum (Ascomycota). Several taxa left few (e.g., nondistinctive spores) or no identifiable cellular remains. Conclusions.Consistent with previous reports, melanized structures tended to be hydrolysis resistant. Retention by modern liverwort-associated glomalean fungi of diagnostic hyphal and spore features after acetolysis indicates high potential for fossilization even under suboptimal conditions, supporting a previous classification of microfossils extracted from Ordovician carbonates. Acetolysis results were also consistent with interpretation of particular Silurian-Devonian macrofossils as plant-microbial consortia.
- 出版日期2017-5
