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Revealing rangeomorph species characters using spatial analyses

Accepted version
Peer-reviewed

Type

Article

Change log

Authors

Mitchell, EGH 
Kenchington, Charlotte  ORCID logo  https://orcid.org/0000-0002-8201-8786
Harris, Simon 
Wilby, Philip 

Abstract

Rangeomorphs dominate the Ediacaran Avalonian macrofossil assemblages of Charnwood Forest, UK (~562Ma). However, their unfamiliar fractal architecture makes distinguishing phylogenetically reliable characters from intraspecific features difficult. Fortunately, spatial analysis of large in-situ populations offers an independent means of assessing their taxonomy. Populations of a single biological species are likely to exhibit similar spatial distributions due to their shared responses to the biological and ecological processes acting upon them. As such, spatial analyses can be used to interrogate which are the most taxonomically deductive characters in similar species. We used Random Labelling Analyses to investigate the presence/absence of characters of Primocandelabrum boyntoni, P. aethelfalaedia and P. aelfwynnia on the North Quarry ’B’ surface. The resultant spatial distributions were compared to observed characters using goodness-of-fit tests to determine which characters were associated with unique populations, and which were found across multiple populations. We found that P. boyntoni and P. aelfwynnia had statistically indistinguishable character distributions, suggesting that they represent a single biological species, and that they exhibited significantly different distributions to P. aethelfalaedia, suggesting that there are two (rather than three) Primocandelabrum species present on the B surface. Furthermore, we found that the distribution of Concealed versus Unconcealed 1st order branches across all specimens exhibited significantly different, density-dependant behaviour, with Unconcealed branching occurring in areas of higher density populations, and Concealed branching occurring in the lower Primocandelabrum density areas. We speculate that unconcealed branches may have been a response to the reduced availability of resources in higher density areas, implying rangeomorphs were capable of ecophenotypic responses.

Description

Keywords

37 Earth Sciences

Journal Title

Canadian Journal of Earth Sciences

Conference Name

Journal ISSN

0008-4077
1480-3313

Volume Title

Publisher

National Research Council Canada
Sponsorship
Natural Environment Research Council (NE/P002412/1)
EGM has been supported by the Natural Environment Research Council [grant number NE/P002412/1], Gibbs Travelling Fellowship from Newnham College, Cambridge and a Henslow Research Fellowship from Cambridge Philosophical Society. Phil Vixseboxse is thanked for his help in producing the RTIs. CGK and PRW were funded by National Environment Research Council grant NE/1005927/1. CGK also acknowledges a Research Studentship funded by the Cambridge Philosophical Society.