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Low tropical diversity during the adaptive radiation of early land plants

Nature Plants volume 8, pages 104–109 (2022)Cite this article

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Abstract

The latitudinal biodiversity gradient, with tropical regions acting as ‘evolutionary cradles’, is a cornerstone of current biogeographical and ecological theory1. In the modern world floral biodiversity and biomass are overwhelmingly concentrated in the tropics, and it is often assumed that the tropics were evolutionary cradles throughout land plant evolutionary history. For example, the origination and diversification of angiosperms is believed to have taken place in the Cretaceous tropics2 and modern gymnosperms in the Permian tropics3. Here, we show that during the first major diversification of land plants, in the Late Silurian–Early Devonian, land plant biodiversity was much lower at the equator compared to medium-high southern latitudes. Throughout this crucial interval of plant evolution, tropical vegetation remained depauperate and of very low taxonomic biodiversity, although with similar morphological disparity to the more diverse higher latitude floras. Possible explanations for this low tropical floral biodiversity include palaeocontinental configuration or adverse palaeotropical environmental conditions. We discount the possibility that it was simply a fortuitous feature of the biogeographical spread of the earliest vascular land plants.

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Fig. 1: Geology of the Lochkovian Red Bay Group of Spitsbergen.
Fig. 2: Dispersed spores and plant megafossils from the Red Bay Group of Spitsbergen.

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All data are available from the corresponding author.

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Acknowledgements

The 2018 expedition to northern Spitsbergen was funded by National Geographic Society grant CP-131R-17. We thank the Governor of Svalbard for permission to undertake the fieldwork (RiS-ID 10970).

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Authors and Affiliations

  1. School of Biosciences, University of Sheffield, Western Bank, Sheffield, UK

    Charles H. Wellman

  2. School of Earth & Ocean Sciences, Cardiff University, Park Place, Cardiff, UK

    Christopher M. Berry & Amy Wyatt

  3. Department of Earth Sciences, University of Cambridge, Cambridge, UK

    Neil S. Davies

  4. Natural History Museum, University of Oslo, Oslo, Norway

    Franz-Josef Lindemann

  5. School of Ocean and Earth Science, University of Southampton, National Oceanography Centre, Southampton, UK

    John E. A. Marshall

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  1. Charles H. Wellman
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Contributions

C.M.B., N.D., F.-J.L., J.E.A.M. and C.H.W. participated in the expedition to northern Spitsbergen and were involved in geological–stratigraphical–sedimentological interpretation and collecting samples for palynological/palaeobotanical analysis. C.H.W. undertook the palynological research and created the spore diversity and disparity database. C.M.B. and A.W. undertook the palaeobotanical research. All authors contributed to the design of the project, the interpretation of the data and the writing of the manuscript.

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Correspondence to Charles H. Wellman.

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Nature Plants thanks Alexander Hetherington and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Information

Supplementary text, Tables 11-13 and references.

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Supplementary Tables

Supplementary Tables 1–10 giving spore diversity and disparity.

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Wellman, C.H., Berry, C.M., Davies, N.S. et al. Low tropical diversity during the adaptive radiation of early land plants. Nat. Plants 8, 104–109 (2022). https://doi.org/10.1038/s41477-021-01067-w

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