JDJCSET | Sigma Xi Poster Competition

Title

A Quantitative Analysis of Shell Shape Variation within Astarte (Class: Bivalvia) from the Atlantic Coastal Plain

Academic Level at Time of Presentation

Graduate

Major

Geosciences

Minor

None

List all Project Mentors & Advisor(s)

Dr. Michelle Casey

Presentation Format

Poster Presentation

Abstract/Description

The Atlantic Coastal Plain has long been recognized as a natural laboratory useful for testing hypotheses about various environmental and ecological effects on marine fauna. A reliable taxonomy for genera, such as Astarte, within the Atlantic Coastal Plain allows these rigorous tests to be performed. The bivalve genus Astarte has many species that have been formally named and identified. A lack of diversification within this genus has been noted by prior authors and anecdotal evidence suggests that some species lack true difference in shape. These bivalves have complex morphologies, making them good candidates for a study using geometric morphometrics to discriminate legitimate species. A preliminary dataset of 46 shells representing four different species from the Pliocene of the Atlantic Coastal Plain were digitally imaged for this study. A total of six landmarks and four pseudo-landmarks were collected. Procrustes analysis was performed to align and resize all individuals for multivariate analysis. Principle Components Analysis was conducted, with PC1 and PC2 accounting for 51.4% of variation. Astarte concentrica showed the most variation as it overlapped with the other species, but still partially occupied its own morphospace. However, Canonical Variate Analysis showed there was minimal significance within this overlap. One specimen of Astarte undulata was classified as Astarte concentrica, while the others were all classified into their own species. If this pattern is robust to the addition of more individuals and species, the data collected can be used to pinpoint morphological differences between the species, which will aid in identification of species studied.

Affiliations

Sigma Xi Poster Competition--ONLY

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A Quantitative Analysis of Shell Shape Variation within Astarte (Class: Bivalvia) from the Atlantic Coastal Plain

The Atlantic Coastal Plain has long been recognized as a natural laboratory useful for testing hypotheses about various environmental and ecological effects on marine fauna. A reliable taxonomy for genera, such as Astarte, within the Atlantic Coastal Plain allows these rigorous tests to be performed. The bivalve genus Astarte has many species that have been formally named and identified. A lack of diversification within this genus has been noted by prior authors and anecdotal evidence suggests that some species lack true difference in shape. These bivalves have complex morphologies, making them good candidates for a study using geometric morphometrics to discriminate legitimate species. A preliminary dataset of 46 shells representing four different species from the Pliocene of the Atlantic Coastal Plain were digitally imaged for this study. A total of six landmarks and four pseudo-landmarks were collected. Procrustes analysis was performed to align and resize all individuals for multivariate analysis. Principle Components Analysis was conducted, with PC1 and PC2 accounting for 51.4% of variation. Astarte concentrica showed the most variation as it overlapped with the other species, but still partially occupied its own morphospace. However, Canonical Variate Analysis showed there was minimal significance within this overlap. One specimen of Astarte undulata was classified as Astarte concentrica, while the others were all classified into their own species. If this pattern is robust to the addition of more individuals and species, the data collected can be used to pinpoint morphological differences between the species, which will aid in identification of species studied.