JDJCSET | Sigma Xi Poster Competition

Title

A Quantitative Analysis of Astarte (Bivalvia: Astartidae) from the Pliocene of the Atlantic Coastal Plain

Academic Level at Time of Presentation

Graduate

Major

Geosciences

List all Project Mentors & Advisor(s)

Michelle Casey, PhD; Kate He, PhD

Presentation Format

Poster Presentation

Abstract/Description

The Atlantic Coastal Plain has long been recognized as a natural laboratory for testing hypotheses about various environmental and ecological effects on marine fauna. A reliable taxonomy for genera within the Atlantic Coastal Plain would allow these studies to conducted rigorously and produce easily repeatable results. The bivalve genus Astarte has many formally named species, even though previous work has noted a lack of features that would encourage diversification. A morphometric analysis of 918 specimens representing 10 species from the Pliocene was conducted. A total of 9 geometric landmarks and 5 pseudo-landmarks were collected from scaled digital photographs. Procrustes transformation and Principal Components Analysis (PCA) were then performed on the collected dataset. A cluster analysis was also performed to recognize subsets of the data and compare them to subsets found within the PCA analysis.

The PCA results show a large amount of overlap between all species, and not the cleanly separate groups one would expect. PC1 and PC2 account for 50.6% of the overall variance, with Astarte concentrica and Astarte undulata showing the highest amounts of phenotypic variation. These two species occupy their own morphospace, while the remaining species typically fall within the broad overlap of A. concentrica and A. undulata. The cluster analysis showed the optimum number of groups to be only 3, when using a centroid clustering method. These results show there is a potential to synonymize the species within this genus and provide an easier to manage and more reliable taxonomy for this group.

Spring Scholars Week 2018 Event

Sigma Xi Poster Competition

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A Quantitative Analysis of Astarte (Bivalvia: Astartidae) from the Pliocene of the Atlantic Coastal Plain

The Atlantic Coastal Plain has long been recognized as a natural laboratory for testing hypotheses about various environmental and ecological effects on marine fauna. A reliable taxonomy for genera within the Atlantic Coastal Plain would allow these studies to conducted rigorously and produce easily repeatable results. The bivalve genus Astarte has many formally named species, even though previous work has noted a lack of features that would encourage diversification. A morphometric analysis of 918 specimens representing 10 species from the Pliocene was conducted. A total of 9 geometric landmarks and 5 pseudo-landmarks were collected from scaled digital photographs. Procrustes transformation and Principal Components Analysis (PCA) were then performed on the collected dataset. A cluster analysis was also performed to recognize subsets of the data and compare them to subsets found within the PCA analysis.

The PCA results show a large amount of overlap between all species, and not the cleanly separate groups one would expect. PC1 and PC2 account for 50.6% of the overall variance, with Astarte concentrica and Astarte undulata showing the highest amounts of phenotypic variation. These two species occupy their own morphospace, while the remaining species typically fall within the broad overlap of A. concentrica and A. undulata. The cluster analysis showed the optimum number of groups to be only 3, when using a centroid clustering method. These results show there is a potential to synonymize the species within this genus and provide an easier to manage and more reliable taxonomy for this group.