Ecological drivers of the Ediacaran-Cambrian diversification of Metazoa |
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Authors: | Douglas H Erwin Sarah Tweedt |
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Institution: | (1) Department of Paleobiology, MRC-121, National Museum of Natural History, P.O. Box 37012, Washington, DC 20013-7012, USA;(2) Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, NM 87501, USA;(3) Behavior, Ecology, Evolution and Systematics (BEES), University of Maryland, College Park, MD 20742, USA |
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Abstract: | Organismal modifications to their physical and chemical environment play a significant role in structuring many modern ecosystems,
and experimental evidence suggests that such behavior can increase diversity. Despite the important role such activities play
in connecting ecology and evolution, less is known of the macroevolutionary impact of such influences, especially their role
during major evolutionary transitions. The Ediacaran-Cambrian diversification of Metazoa encompassed the appearance and early
diversification of virtually all major clades of marine animals and the establishment of metazoan-dominated ecosystems. Here
we assess the role of positive ecological feedbacks using a new compilation of the first occurrences of all metazoan phyla,
classes; orders and equivalent stem taxa, as well as data from a previously published compendium on fossils from the early
to middle Cambrian of China. The results reveal relatively minor feedback during the Ediacaran, but a substantial increase
during the Cambrian, principally through bioturbation and the appearance of a number of structural engineers, including sponges.
Chemical modification of the environment through filtering and bioturbation seems to have had the largest impact. Data on
taxic diversity is a poor proxy for abundance, or for the actual environmental impact of these activities, however. Future
assessments of the influence of ecological feedbacks on this event will require standardized assessments of the abundance
of taxa with different ecological roles. |
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Keywords: | |
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