Complexity in the oldest animal ecosystems

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The Ediacaran Period (635-541 Ma) captures a fundamental stage in the evolution of complex life. Typifying this time are the Ediacara biota, a globally distributed group of large, soft-bodied, morphologically complex multicellular organisms whose biological affinities are strongly contested. My research combines data-driven modeling and advanced instrumentation with experimental procedures and field work into a single research program targeting three fundamental questions: 1) to what extent is preservation biasing the fossil record of early life? 2) How did the Ediacara biota perform basic biological functions? And 3) how complex were the oldest animal ecosystems? Preservational biases must be considered when evaluating the fidelity of the fossil record. My research group applies multidisciplinary laboratory-based investigations into soft-tissue fossilization by designing decay chambers that continuously monitor and report the geological, biological, and chemical products of decay (pH, CO2, H2S, CH4, NO2, etc.), in addition to sediment/liquid/gas extraction tools that allow for sampling with minimal disruption. Through this approach, we are able to identify key stages in the tempo and mode of exceptional fossilization, and set realistic limits on the fidelity of the fossil record of early life. In order to address the biological functions of the Ediacara biota, I combine phylogenetic studies with functional morphology. My research group has pioneered the use of digital reconstructions of Ediacaran organisms subjected to virtual oceanic conditions to demonstrate alternative feeding strategies and even propose mobility in forms that lack fossilized appendages. My approaches target how individual species interacted within an ecosystem, leading to evaluations of the hidden complexity within Ediacaran ecosystems. As ecosystem complexity can be investigated in many ways, my laboratory has developed innovative fuzzy ecospace modelling approaches that target the evolution, expansion, and even loss of strategic positions occupied by organisms within an ecosystem (i.e. niche). Given their antiquity, Ediacaran ecosystems are typically interpreted as relatively simple. However, paleoecological studies stemming from my research have demonstrated 1) the likelihood of competitive interactions between many Ediacara biota leading to speciation, 2) expanded reproductive strategies among the oldest Ediacara biota, 3) expanded trophic structure in the latest Ediacaran with the advent of penetrative burrowing and predation, and 4) a greater diversity of mobile Ediacara biota than previously hypothesized. Targeted field programs in Namibia and Iran will provide the data necessary to evaluate how niche creation, occupation, and destruction has changed throughout the Ediacaran and into the Cambrian. Ultimately, my research will be central to evaluating the magnitude of biotic interactions and turnover at the dawn of animal life.