Sporopollenin chemistry: a treasure-trove to plunder

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Abstract

The spore and pollen fossil archive represents one of, if not the most complete records of life that is available to palaeobotanists. This record is driven by separate but complementary aspects; production in truly vast numbers combined with their highly recalcitrant chemistry. The end result of these factors is a high fidelity (temporal and spatial) fossil record which has been used to answer big picture questions such as the origins of land plants, the radiation of angiosperms and the terrestrial response to mass extinction events to both determine the degree of extinction and infer climate change. These discoveries have been based on identifying biological affinities of fossils while changes in composition through time have been used to infer climate change. Effectively the sporomorph record has been used as a passive archive for monitoring species occurrence, abundance and diversity though time. However one factor that has stymied palynological research is the lack of taxonomic resolution with identification at the species level often proving very problematic if not impossible. A well-known example of this problem is the grasses, which despite comprising ~11 500 species are often recorded as one pollen morphotype. These issues often become more problematic with increasing age and a loss of recognisable relatives. Over the last decade we have been looking at specific aspects of sporopollenin chemistry to establish if this biomacromolecule can be used to as a proxy to track changes in UV-B radiation and from this infer changes in total solar irradiance. Our work has emphasised that the chemical composition of sporopollenin is plastic and that these chemical signals reflect changes in the light environment in which the plant grew. The stability of sporopollenin means that this primary biogeochemistry is preserved through a wide diagenetic window, allowing for this information to be extracted from suites of fossil spores and pollen grains. Furthermore, broad brush fingerprinting of sporopollenin has revealed that a significant taxonomic signature can be recovered from pollen grains and that aspects of pollen chemistry appear to be influenced by temperature. These findings, together with ever improving analytical capabilities offer the potential for the fossil spore and pollen archive to be used in a dynamic manner to address long standing and newly emerging questions linked to the evolution of the terrestrial biosphere. This presentation will outline these findings and the exciting possibilities that are achievable.

Speakers from the University of Münster

Jardine, Phillip

Professur für Paläobotanik (Prof. Kerp)