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Research Team
Research Team
Santina Celli
Santina Celli
Undergraduate Researcher,
Biology
Alex Dunahoo
Alex Dunahoo
Graduate Student Mentor,
Biology
Introduction
Introduction
The Purple Lilliput (Toxolasma lividum) is a freshwater mussel from the Interior (Ozark) and Appalachian Highlands. The Interior Highlands is an endemicity hotspot, meaning that many species are found only there. Preliminary eDNA analysis revealed Ozarkian sequences that are distinct from Appalachian references.
Figure 1:
Figure 1:
Images of the Purple Liliput (T. lividum) to show its morphological features. This freshwater mussel gets its name from the distinct purple color of its nacre (mother of pearl). Photos from iNaturalist user jeffgarner.
Hypothesis
Hypothesis
T. lividum from the Interior Highlands is an undescribed species
Aims and Goals
Aims and Goals
Sequence DNA from T. lividum individuals within and outside of the Interior Highlands
Perform a phylogenetic assessment of the T. lividum species complex
Methods
Methods
Collected DNA from museum tissues and living individuals (using non-lethal swabs)
Performed PCR to amplify the COI and NDI genes, followed by Sanger sequencing
Created maximum likelihood tree using a concatenated sequence dataset
Findings and Discussion
Findings and Discussion
The maximum-likelihood bootstrap consensus tree generated using concatenated sequences of the COI and NDI genes displayed very high confidence at nodes that separated the T. lividum individuals into two distinct clades. Mapping the individuals where they were found between the Interior and Appalachian Highlands revealed that this pattern is geographically structured as well. This means that the individuals phylogenetically within the Appalachian clade were found in the Appalachian Highlands, while the individuals phylogenetically within the Interior Highland clade were found in the Interior Highlands. This is strong evidence that the T. lividum found in the Interior Highlands may be an undescribed species. Then the genetic diversity of both clades was calculated, and it was found that the Interior Highlands were more diverse, which may be because we had more samples from the Interior Highlands.
This is important overall because T. lividum was a candidate for ESA listing 3, but was rejected for this protection. If T. lividum is in fact 2 species/sub species, listing may be required to sustain one or both lineages. The Appalachian Highlands lineage may be at higher risk because of its possible lack of genetic diversity. Additional research is required, though, before a species distinction can be applied.
Figures
Figures
Figure 2:
Figure 2:
Maximum-likelihood bootstrap consensus trees based on concatenated COI and ND1 sequences. Trees were generated using 1,000 bootstrapped replicates. Only bootstrap support values >= 0.80 are displayed. Toxolasma parvum was used as an outgroup. Red diamonds represent individuals from the Interior Highlands, and blue diamonds represent individuals from the Appalachian Highlands.
Figure 3:
Figure 3:
Map of sequenced individuals. Red diamonds represent individuals assigned to the Interior Highlands clade, and blue diamonds represent individuals assigned to the Appalachian Highlands clade. Polygons indicate the historical range of T. lividum.
Table 1:
Table 1:
Genetic diversity summary statistics for T. lividum clades. Number of individuals (N), number of haplotypes (h), haplotype diversity (Hd), nucleotide diversity (π), and average number of nucleotide differences between individuals of the same clade (k).
Next Steps
Next Steps
The next steps of this project are to collect more tissue samples from more T. lividum individuals to sequence and analyze the ITS and 28S genes. We will also perform morphological analysis of museum vouchers of T. lividum to determine defining features between and among individuals of each clade.
Acknowledgements
Acknowledgements
Kentaro Inuoe and others who provided tissue samples for DNA extraction.
Dave Berg for mentoring through the process of developing and executing this research project and providing helpful feedback when we needed it.
NACE Career Readiness Competencies
NACE Career Readiness Competencies
Career and Self Development: My ideal future career is in research, and this opportunity has
Communication: My communication skills have grown from relying on communication with my grad student mentor and faculty mentor about roadblocks in my research and developing this presentation.
Critical Thinking: I have needed to problem-solve over the course of this project, which has led to necessary critical thinking about all the best ways to solve my problems.
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