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- Title
- Genomic basis of electric signal variation in African weakly electric fish
- Creator
- Losilla-Lacayo, Mauricio
- Date
- 2021
- Collection
- Electronic Theses & Dissertations
- Description
-
A repeated theme in speciation is reproductive isolation centered around divergence in few, highly variable traits, specially in cases without strong geographic isolation and high speciation rates. Understanding the genomic basis of highly variable traits that are key to speciation is a major goal of evolutionary biology, because they can characterize crucial drivers and foundations of the speciation process. African weakly electric fish (Mormyridae) are a decidedly speciose clade of teleost...
Show moreA repeated theme in speciation is reproductive isolation centered around divergence in few, highly variable traits, specially in cases without strong geographic isolation and high speciation rates. Understanding the genomic basis of highly variable traits that are key to speciation is a major goal of evolutionary biology, because they can characterize crucial drivers and foundations of the speciation process. African weakly electric fish (Mormyridae) are a decidedly speciose clade of teleost fish, and their electric organ discharges (EODs) are highly variable traits central to species divergence. However, little is known about the genes and celullar processes that underscore EOD variation. In this dissertation, I employ RNAseq and Nanopore sequencing to study the genomic basis of electric signal variation in mormyrids. In Chapter 1, I take a transcriptome-wide approach to describe the molecular basis of electric signal diversity in species of the mormyrid genus Paramormyrops, divergent for EOD complexity, duration and polarity. My results emphasize genes that influence the shape and structure of the electrocyte cytoskeleton, membrane, and extracellular matrix, and the membrane’s physiological properties. In Chapter 2, I compare gene expression patterns between electric organs that produce long vs short EODs. The results strongly support known aspects of morphological and physiological bases of EOD duration, and for the first time I identified specific genes and broad cellular processes expected to that alter morphological and physiological properties of electrocytes, most striking among these is the differential expression of multiple potassium voltage-gated channels. These two chapters independently identified the gene epdl2 as of interest for EOD divergence. In Chapter 3, I study the molecular evolutionary history of epdl2 in Mormyridae, with emphasis on Paramormyrops. My results suggest that three rounds of gene duplication produced four epdl2 paralogs in a Paramormyrops ancestor. In addition, I identify ten sites in epdl2 expected to have experienced strong positive selection in paralogs and implicate them in key functional domains. Overall, the results of this dissertation greatly solidify and expand our understanding of how the genome underpins changes to electrocytes, and in turn, divergence in their electric signals, a highly variable trait that may facilitate speciation in African weakly electric fish. This work provides an evidence-grounded list of candidate genes for functional analyses aimed to corroborate their contribution to the EOD phenotype.
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