Morphology shapes community dynamics in early animal ecosystems
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Abstract
The driving forces behind the evolution of early metazoans are not well understood, but key insights into their ecology and evolution can be gained through ecological analyses of the in situ, sessile communities of the Avalon assemblage in the Ediacaran (~565 million years ago). Community structure in the Avalon is thought to be underpinned by epifaunal tiering and ecological succession, which we investigate in this study in 18 Avalon communities. Here we found that Avalon communities form four distinctive Community Types irrespective of succession processes, which are instead based on the dominance of morphologically distinct taxa, and that tiering is prevalent in three of these Community Types. Our results are consistent with emergent neutrality, whereby ecologically specialized morphologies evolve as a consequence of neutral (stochastic or reproductive) processes within niches, leading to generalization within the frond-dominated Community Type. Our results provide an ecological signature of the first origination and subsequent loss of disparate morphologies, probably as a consequence of community restructuring in response to ecological innovation. This restructuring led to the survival of non-tiered frondose generalists over tiered specialists, even into the youngest Ediacaran assemblages. Such frondose body plans also survive beyond the Ediacaran–Cambrian transition, perhaps due to the greater resilience afforded to them by their alternative ecological strategies.
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Acknowledgements: Funding was provided by an School of Biological Sciences Balfour Studentship (PFAG/076) to N.P.S.; a Natural Environment Research Council C-CLEAR DTP studentship (LBAG/265.03.G10) to K.M.D.; Leverhulme Trust Funding (ECF-2018-542) and from the Isaac Newton Trust (INT18.08(h)) to C.G.K.; a Natural Environment Research Council Standard Grant (NE/P002412/1) and an Independent Research Fellowship (NE/S014756/1) to E.G.M. The Parks and Natural Areas Division, Department of Environment and Conservation, Government of Newfoundland and Labrador, provided permits to conduct research within the MPER in 2010, 2016–2018 and 2021–2023. Readers are advised that access to MPER is by scientific research permit only. Fossil surfaces in the Bonavista Peninsula and Bay Roberts area are protected under reg. 67/11, of the Historic Resources Act 2011 and their access is only allowed under permit from the Government of Newfoundland and Labrador. Fieldwork in the Discovery Geopark and the Bay Roberts area was conducted under permit from the Government of Newfoundland and Labrador. Bed B forms part of a designated Site of Special Scientific Interest, protected in law and administered by Natural England. Access to Bed B casts was facilitated by BGS and P. Wilby. We thank S. Pates and F. Dunn for discussions, B. Jewer for image processing and J. Durden for support with the methods. We thank E. Samson for everything she does to support us and our work.
Funder: Independent Research Fellowship NE/S014756/1
Funder: School of Biological Science Balfour Studentship
Funder: RCUK | Natural Environment Research Council (NERC); doi: https://doi.org/10.13039/501100000270
Funder: ECF-2018-542, INT18.08(h)
