High ecological complexity in benthic Ediacaran communities

Abstract

A long-running debate over the affinities of the Neoproterozoic ‘Ediacara biota’ has led to contrasting interpretations of Ediacaran ecosystem complexity. A ‘simple’ model assumes that most, if not all, Ediacaran organisms shared similar basic ecologies. A contrasting ‘complex’ model suggests that the Ediacara biota more likely represent organisms from a variety of different positions on the eukaryotic tree and thus occupied a wide range of different ecologies. We perform a quantitative test of Ediacaran ecosystem complexity using rank abundance distributions (RADs). We show that the Ediacara biota formed complex-type communities throughout much of their stratigraphic range and thus likely comprised species that competed for different resources and/or created niche for others (‘ecosystem engineers’). One possible explanation for this pattern rests in the recent inference of multiple metazoan-style feeding modes among the Ediacara biota; in this scenario, different Ediacaran groups/clades were engaged in different methods of nutrient collection and thus competed for different resources. This result illustrates that the Ediacara biota may not have been as bizarre as it is sometimes suggested, and provides an ecological link with the animal-dominated benthic ecosystems of the Palaeozoic era.

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Fig. 1: Examples of Ediacaran in situ communities preserved on bedding planes.
Fig. 2: Distribution of 'simple' (geometric, log-series and zero-sum multinomial) and 'complex' (log-normal and Zipf) RADs throughout the Ediacaran period.
Fig. 3: The effects of three ‘guilds’ within a community (illustrated using different colours) utilizing separate resources and following independent geometric RADs.

Data availability

All R code and data are provided in the online supplementary materials.

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Acknowledgements

S.A.F.D. was funded by a Smithsonian Institution Peter Buck Postdoctoral Fellowship. M.L. and S.A.F.D. also acknowledge generous funding from a National Geographic Research and Exploration Grant (9241-13), which allowed collection of Ediacaran population data from Namibia. This is Paleobiology Database Publication 318.

Author information

S.A.F.D. and M.L. collected and compiled the data. P.J.W. and S.A.F.D. performed the analyses. All authors contributed to writing the paper.

Correspondence to Simon A. F. Darroch.

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Supplementary information

Supplementary Information

Supplementary tables, figures and references

Reporting Summary

Supplementary Dataset 1

Excel file detailing the taxonomic composition (and assignments) for all assemblages used in analyses

Supplementary Dataset 2

R code written and used by the authors to calculate RAD fits for Ediacaran datasets

Supplementary dataset 3

txt file for use with R code, providing relative abundances of Ediacaran taxa within studied assemblages

Supplementary dataset 4

txt file for use with R code, providing the names of assemblages used in analyses

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