International Journal of Molecular Evolution and Biodiversity 2024, Vol.14, No.3, 120-132 http://ecoevopublisher.com/index.php/ijmeb 124 3 Genetic Insights from Phylogenetic Studies 3.1 Genetic diversity in cassava Phylogenetic studies have provided significant insights into the genetic diversity present within cassava populations, which is crucial for understanding its history of domestication. Studies have shown that the genetic variation in domesticated cassava (Manihot esculenta subsp. esculenta) is a subset of that found in its wild relatives, indicating that the domesticated variety was derived solely from its conspecific wild relative, M. esculenta subsp. Flabellifolia (Olsen and Schaal, 2001). This is further supported by the presence of shared alleles between domesticated cassava and a specific geographical subset of wild Manihot populations, suggesting a single domestication event fromM. esculenta subsp. flabellifolia in the southern Amazon basin (Olsen, 2004). Simon et al. (2021) estimated ancestral states for habitat type and geographicregion throughout our concatenated nuclear genomic tree afterpruning tips to remove species replicates (Figure 3). Additionally, traditional farming practices, such as the incorporation of volunteer seedlings from sexual reproduction into the stock of varieties grown, have been shown to maintain a high level of genetic diversity within cassava populations (Elias et al., 2000). Figure 3 Ancestral state reconstruction (ASR) of habitat duringManihot diversification (Photo credit: Simon et al., 2021) Image caption: ‘Habitat’ pies show thefraction of taxa within each clade corresponding to each habitat type, and ‘Region’ pies show the fraction of taxa corresponding to the geographic zoneson the map. ‘Combination’ habitats on internal nodes with ≥25% probability have their contributing habitats shown with bars to the left (Adopted from Simon et al., 2021) This figure drawn by Simon et al. (2021) provides a detailed visual representation of the ancestral habitats and geographic regions associated with Manihot diversification. The use of pie charts to represent habitat and region fractions offers a clear and concise way to visualize the ecological and geographical distribution of these taxa. The figure underscores the complexity and diversity of Manihot species' habitats, highlighting how different environmental conditions have influenced their evolutionary trajectories. The comprehensive approach to ASR, including the removal of species replicates, ensures accurate and meaningful insights into the evolutionary history of this genus. 3.2 Wild relatives and ancestral species The wild relatives of cassava, particularly M. esculenta subsp. flabellifolia, have been identified as the closest wild relative and likely the progenitor species of domesticated cassava (Olsen and Schaal, 2001). Phylogenetic studies using microsatellite loci and single-copy nuclear genes like G3pdh have provided evidence that cassava was domesticated from wild populations along the southern border of the Amazon basin (Olsen and Schaal, 1999). Contrary to previous beliefs, cassava does not appear to be derived from multiple progenitor species or from hybridization with closely related species such as M. pruinosa(Olsen and Schaal, 1999).
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