Title

Morphometric Variability within Astarte (Class: Bivalvia) 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

Presentation Format

Oral Presentation

Abstract/Description

The bivalve genus Astarte is a cosmopolitan genus that is commonly found within the Atlantic Coastal Plain of the United States. This genus has many formally named species, even though it lacks many features that would encourage diversification. As a result, the validity of some Astarte taxa have been called into question. A well-defined taxonomy is a key component to the reliable testing of paleoecological hypotheses. 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) was performed on the collected dataset.

The PCA results show a large amount of overlap between all species. Astarte concentrica and Astarte undulata show the most phenotypic variation. These two species occupy their own morphospace, with a large amount of overlap. The remaining species show considerable overlap with each other and A. concentrica and A. undulata. Since most of these species fall within the overlapped-morphospace, they demonstrate intermediate morphologies between A. concentrica and A. undulata.

These species merit a further look as several of them could likely be synonymized. The potential to synonymize several species within this genus could provide an easier to manage and more reliable taxonomy within the Atlantic Coastal Plain. This cleaner taxonomic group will allow for more rigorous and easily replicable studies to be conducted using these species.

Spring Scholars Week 2018 Event

Watershed Research Institute Symposium

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Morphometric Variability within Astarte (Class: Bivalvia) from the Pliocene of the Atlantic Coastal Plain

The bivalve genus Astarte is a cosmopolitan genus that is commonly found within the Atlantic Coastal Plain of the United States. This genus has many formally named species, even though it lacks many features that would encourage diversification. As a result, the validity of some Astarte taxa have been called into question. A well-defined taxonomy is a key component to the reliable testing of paleoecological hypotheses. 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) was performed on the collected dataset.

The PCA results show a large amount of overlap between all species. Astarte concentrica and Astarte undulata show the most phenotypic variation. These two species occupy their own morphospace, with a large amount of overlap. The remaining species show considerable overlap with each other and A. concentrica and A. undulata. Since most of these species fall within the overlapped-morphospace, they demonstrate intermediate morphologies between A. concentrica and A. undulata.

These species merit a further look as several of them could likely be synonymized. The potential to synonymize several species within this genus could provide an easier to manage and more reliable taxonomy within the Atlantic Coastal Plain. This cleaner taxonomic group will allow for more rigorous and easily replicable studies to be conducted using these species.