Population structure of the oldest known macroscopic communities from Mistaken Point, Newfoundland

The presumed affinities of the Terminal Neoproterozoic Ediacara biota have been much debated. However, even in the absence of concrete evidence for phylogenetic affinity, numerical paleoecological approaches can be effectively used to make inferences about organismal biology, the nature of biotic in...

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Bibliographic Details
Published in:Paleobiology 2013-09, Vol.39 (4), p.591-608
Main Authors: Darroch, Simon A. F, Laflamme, Marc, Clapham, Matthew E
Format: Article
Language:English
Subjects:
allometry
Astrobiology
Avalon Peninsula
Benthic fauna
Beothukis
Biota
Cambrian
Canada
communities
Eastern Canada
Ediacaran
Endangered & extinct species
Fossils
Fractals
Fractofusus misrai
Geology
growth
histograms
Life history
Marine ecology
Mistaken Point Ecological Reserve
Neoproterozoic
Newfoundland
Newfoundland and Labrador
Organic matter
Organismal biology
Paleobiology
Paleoecology
Paleontology
Pectinifrons
Phylogenetics
Population ecology
Population structure
populations
Precambrian
problematic fossils
Proterozoic
Rangeomorpha
reproduction
s
statistical analysis
Statistical variance
Taxa
Taxonomy
Thectardis
upper Precambrian
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Summary:The presumed affinities of the Terminal Neoproterozoic Ediacara biota have been much debated. However, even in the absence of concrete evidence for phylogenetic affinity, numerical paleoecological approaches can be effectively used to make inferences about organismal biology, the nature of biotic interactions, and life history. Here, we examine the population structure of three Ediacaran rangeomorph taxa (Fractofusus, Beothukis, and Pectinifrons), and one non-rangeomorph taxon (Thectardis) across five fossil surfaces around the Avalon Peninsula, Newfoundland, through analysis of size-frequency distributions using Bayesian Information Criterion (BIC). Best-supported models resolve communities of all studied Ediacaran taxa at Mistaken Point as single cohorts with wide variance. This result is best explained in terms of a “continuous reproduction” model, whereby Ediacaran organisms reproduce aseasonally, so that multiple size modes are absent from preserved communities. Modern benthic invertebrates (both as a whole and within specific taxonomic groups) in deeper-water settings reproduce both seasonally and aseasonally; distinguishing between biological (i.e., continuous reproductive strategies) and environmental (lack of a seasonal trigger) causes for this pattern is therefore difficult. However, we hypothesize that the observed population structure could reflect the lack of a trigger for reproduction in deepwater settings (i.e., seasonal flux of organic matter), until the explosive appearance of mesozooplankton near the base of the Cambrian.
ISSN:0094-8373
1938-5331
DOI:10.1666/12051