Palaeobotanical experiences of plant diversity in deep time. 1: How well can we identify past plant diversity in the fossil record?

Palaeobotany and palynology are the main direct sources of evidence for studying vegetation diversity dynamics through geological time. However, plant fossil diversity is affected by various factors other than vegetation diversity, which need to be taken into account in such studies. The use of fossil-taxa will potentially inflate perceived plant diversities, requiring taxonomic lists to be normalised. Autochthonous floras provide the most direct evidence of vegetation diversity but these are rare; most plant beds are allochthonous with plant remains that have been subjected to varying levels of fragmentation, transportation and time averaging. Local-scale vegetation diversity is especially difficult to determine from the fossil record, even with rigorous sampling protocols and detailed sedimentological analysis. Landscape-scale and regional-scale vegetation diversities are more reliably determined but usually at the rank of family. Macrofossil and palynological data tend to reveal evidence of different aspects of plant diversity, and the best results are obtained if the two diversity signals are integrated. Despite the inherent difficulties, the plant fossil record provides clear evidence of the dynamic history of vegetation through geological times, including the effects of major processes such as climate changes and mass extinctions

Palaeobotanical experiences of plant diversity in deep time. 2: How to measure and analyse past plant biodiversity

Determining the diversity of past floras helps with interpreting both the history and predicting the future of vegetation change. For global-scale and regional-scale diversity studies especially, secondary data are often used but local-scale studies tend to be based on survey data that require rigorous sampling. The correct sampling strategies depend on the types of fossils being investigated, including their physical size, and whether the aim is to determine taxonomic richness or relative abundance. Describing and comparing diversities can use a range of different metrics, depending on whether binary presence/absence or abundance data are available. Each metric provides a different insight into the diversities and the choice of which to use depends on the research question being investigated. Various numerical approaches are available for identifying spatial and stratigraphical diversity patterns, mainly classificatory techniques (e.g., cluster and parsimony analyses) and ordination (e.g., Detrended Correspondence Analysis, Nonmetric Dimensional Scaling). The choice of technique again depends on the research question, but often it has proved useful to run both types of analysis in tandem. This article is illustrated by past biodiversity case studies from throughout the fossil record, dealing with floras ranging in age from the Devonian to the last few centuries

Palaeobotanical experiences of plant diversity in deep time. II: How to measure and analyse past plant biodiversity

International audienc