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Morphometric Analysis of the Early Cambrian mollusc Mackinnonia and the Incipient Species Concept
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
(English)In: Palaeontology, ISSN 0031-0239, E-ISSN 1475-4983Article in journal (Other academic) Submitted
Abstract [en]

Phylogenetic relationships within the helcionelloids have been difficult to establish. One of the reasons for this is that qualitative approaches to investigating morphological variation in this group have struggled to identify clear patterns. An alternative method of identifying these patterns is to study these organisms quantitatively. Here we exemplify this approach by employing morphometric methods to investigate patterns of subtle morphological variation in two species of Mackinnonia Runnegar in Bengtson et al. Specifically, we conduct a combination of elliptical Fourier and multivariate analyses to study intra- and interspecific variation in protoconch form and variation in ontogenetic trajectory of two species of Mackinnonia. The material we use consists of two assemblages of Mackinnonia rostrata (Zhou & Xiao), from the Shackleton Limestone of Antarctica and Ajax Limestone of Australia, and an assemblage of Mackinnonia taconica (Landing & Bartowski) from the Bastion Formation of Greenland. Results of our study show significant (p=<0.0001) differences in protoconch shape between all three groups. Ontogenetic sequences of outline curves truncated at successive rugae significantly (p=<0.05) discriminate between M. rostrata and M. taconica. We discuss the uncovered significant intraspecific morphological variation of disparate assemblages of M. rostrata despite shared qualitative features and develop a conceptual framework for understanding such patterns of variation. We define the incipient species concept using Mackinnonia as an empirical example.

National Category
Evolutionary Biology
Identifiers
URN: urn:nbn:se:uu:diva-319485OAI: oai:DiVA.org:uu-319485DiVA: diva2:1087694
Available from: 2017-04-10 Created: 2017-04-10 Last updated: 2017-04-19
In thesis
1. Morphometric analysis of Cambrian fossils and its evolutionary significance
Open this publication in new window or tab >>Morphometric analysis of Cambrian fossils and its evolutionary significance
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The Extended Evolutionary Synthesis (EES) is currently emerging as a theoretical alternative to the Modern Synthesis (MS) in which to frame evolutionary observations and interpretations. These alternative frameworks differ fundamentally in their understanding of the relative roles of the genotype, phenotype, development and environment in evolutionary processes and patterns. While the MS represents a gene-centred view of evolution, the EES instead emphasizes the interactions between organism, development and environment. This novel theoretical framework has generated a number of evolutionary predictions that are mutually incompatible with the equivalent of the MS. While research and empirical testing has begun on a number of these in a neontological context, the field of palaeontology has yet to contribute meaningfully to this endeavour. One of the reasons for this is a lack of methodological approaches capable of investigating relevant evolutionary patterns in the fossil record. In this thesis morphometric methods capable of providing relevant data are developed and employed in the analysis of Cambrian fossils. Results of these analyses provide empirical support for the process of evolution through phenotypic plasticity and genetic assimilation hypothesized by the EES. Furthermore, theoretical revision to the species concept in a palaeontological context is suggested. Finally, predictions of the EES specific to the fossil record are made explicit and promising directions of future research are outlined.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. 63 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1506
Keyword
Extended Evolutionary Synthesis, phenotypic plasticity, genetic assimilation, phenotypic accommodation, Agnostus pisiformis, Mackinnonia, elliptical fourier analysis, species concept
National Category
Evolutionary Biology
Identifiers
urn:nbn:se:uu:diva-319487 (URN)978-91-554-9894-8 (ISBN)
Public defence
2017-06-02, Norrlands 1 & 2, Villavägen 16, Uppsala, 13:00 (English)
Opponent
Supervisors
Available from: 2017-05-12 Created: 2017-04-10 Last updated: 2017-05-16

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