Wilby et al 2015 PPP - low intensity environmental disturbance impacts on Ediacaran macrobenthic communities.pdf (3.29 MB)
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Role of low intensity environmental disturbance in structuring the earliest (Ediacaran) macrobenthic tiered communities

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posted on 28.07.2015 by Philip R. Wilby, C.G. Kenchington, Robert Wilby
Rangeomorphs were important components of Ediacaran macrobenthic ecosystems, yet their biology and ecology remain poorly constrained. They formed high-density, tiered communities that were subjected to intermittent burial events, the largest of which killed entire communities. Abundant thin event beds in the Ediacaran succession of Charnwood Forest indicate the additional, frequent impact of minor obrution events. The type surface of Charnia masoni is immediately underlain by one such lamina (a tuff) and preserves a distinctly bimodal population. It is dominated by Charnia fronds that are of smaller or comparable length to the holotype (19.4. cm), but also includes notably larger specimens (>. 45. cm) that would traditionally have been assigned to Charnia grandis. Multiple morphological- and morphometric parameters (length, width, spacing of primary branches) demonstrate that these are indistinguishable from the holotype of C. masoni, affirming the synonymy of the two taxa. Nevertheless, these outsized individuals are distinguished by their proportionally fewer primary branches per unit length. Taphonomic evidence indicates that they were survivors of an incumbent population, the rest of which was culled by a minor ashfall. We suggest that this temporary reduction in competition from neighbours allowed the survivors to grow larger and thereby gain access to a greater proportion of the water column. As the community recovered, their large size would have continued to provide them with an advantage, divorcing them from the density-dependent competition seen in the new understory. The interlude between cohorts implies that new recruits were substrate-sensitive, presumably awaiting re-establishment of the biomat. Sub-lethal disturbance events thus played a significant role in structuring Ediacaran communities, and help explain the observed bed-by-bed variability. Taken as a whole, the growth trajectory of C. masoni resembles that of extant organisms with indeterminate growth programmes and no genetically-controlled upper size limit.

Funding

PRW and CGK were supported by NERC grant NE/I005927/1

History

School

  • Social Sciences

Department

  • Geography and Environment

Published in

Palaeogeography, Palaeoclimatology, Palaeoecology

Citation

WILBY, P.R., KENCHINGTON, C.G. and WILBY, R.L., 2014. Role of low intensity environmental disturbance in structuring the earliest (Ediacaran) macrobenthic tiered communities. Palaeogeography, Palaeoclimatology, Palaeoecology, 434, pp.14-27.

Publisher

Elsevier / © The Authors

Version

VoR (Version of Record)

Publisher statement

This work is made available according to the conditions of the Creative Commons Attribution 4.0 International (CC BY 4.0) licence. Full details of this licence are available at: http://creativecommons.org/licenses/ by/4.0/

Publication date

2014

Notes

This is an Open Access article published by Elsevier and distributed under the terms of the Creative Commons Attribution Licence http://creativecommons.org/licenses/by/4.0/

ISSN

0031-0182

Language

en

Licence

Exports