| Summary: | The land snail genus Cepaea has long served as a model system for understanding the evolutionary forces shaping phenotypic diversity. This thesis builds on that rich history by integrating genomic, mitochondrial, and phenotypic analyses to uncover new insights into the evolutionary history, genetic architecture, and phenotypic variation of Cepaea hortensis and Cepaea nemoralis.
Leveraging whole-genome sequencing, I reconstructed the phylogeography of C. hortensis, revealing that North American populations cluster with Icelandic populations, indicating a complex historical connection rather than direct descent from a single closely related European population. Further analysis uncovered a geographically isolated North American lineage shaped by historical bottlenecks and genetic drift.
In parallel, I assembled, annotated and then explored the first complete mitochondrial genome of C. hortensis, highlighting significant intraspecific variation, particularly in tRNA-Thr and COX3 copy numbers. These results suggest that heteroplasmy may play a key role in mitochondrial genome evolution, advancing our understanding of gastropod mitochondrial biology and adaptation.
Focusing on C. nemoralis, I investigated the genetic basis of shell colour polymorphism, emphasizing the role of supergenes. My findings show that continuous variation in shell colour is primarily driven by variation at the supergene locus, with additional contributions from unlinked loci. These findings highlight the importance of supergenes and unlinked loci in generating phenotypic diversity.
The thesis makes significant contributions to understanding evolutionary processes in the Cepaea genus, offering insights into adaptation, speciation, and the role of genetic and genomic architecture in phenotypic diversity.
This work lays a foundation for further exploration into the evolutionary genetics of molluscs.
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