Legume Genomics and Genetics 2024, Vol.15, No.1, 37-44 http://cropscipublisher.com/index.php/lgg 39 legumes (Figure 1) (Ren et al., 2018). Another study employed a combination of phylogenetic methods, such as the stepwise AIC approach (MEDUSA), Bayesian mixture model approach (BAMM), and state-dependent diversification analyses (MuSSE), to investigate patterns of diversification following WGD events (Landis et al., 2018). Several key WGD events have been identified in the evolutionary history of legumes. One significant WGD event occurred in the common ancestor of the Papilionoideae subfamily, which includes important crops like soybean, peanut, and common bean (Cannon et al., 2015). This WGD event is believed to have contributed to the diversification and success of this subfamily. Additionally, independent WGDs have been detected near the base of other major legume lineages, such as the Mimosoideae-Cassiinae-Caesalpinieae (MCC) clade, Detarieae, and Cercideae clades (Cannon et al., 2015). These WGDs are associated with the emergence of novel traits and increased species richness in these lineages. 3.2 Case studies of WGD in specific legume lineages The Papilionoideae subfamily, also known as the Faboideae, has experienced significant WGD events that have shaped its evolution. The WGD event in the common ancestor of all papilionoids is a notable example. This event has been linked to the diversification of nodulating and non-nodulating taxa within the subfamily, including economically important crops such as alfalfa, soybean, and common bean (Cannon et al., 2015; Nadon and Jackson, 2020). The polyploid origins of these crops have implications for their domestication and improvement, as polyploidy can generate new functional diversity and drive speciation (Nadon and Jackson, 2020). In the Mimosoideae subfamily, WGDs have also played a crucial role in diversification. The MCC clade, which includes the Mimosoideae, experienced an ancestral WGD event that is associated with the emergence of nodulation, a key trait for nitrogen fixation (Cannon et al., 2015). This WGD event likely contributed to the ecological success and diversification of the Mimosoideae subfamily. The Caesalpinioideae subfamily has also been influenced by WGD events. Independent WGDs have been detected near the base of the Caesalpinioideae lineage, contributing to the diversification of this group (Cannon et al., 2015). These WGDs are associated with the development of novel traits and increased species richness, similar to the patterns observed in other legume subfamilies. In summary, WGD events have had a profound impact on the diversification of legumes, with significant events identified in the Papilionoideae, Mimosoideae, and Caesalpinioideae subfamilies. These events have contributed to the emergence of novel traits, increased species richness, and the ecological success of these lineages. 4 Impacts of WGD on Legume Diversification 4.1 Genetic diversity and evolutionary innovation Whole genome duplication (WGD) events have been pivotal in enhancing genetic diversity and fostering evolutionary innovation in legumes. WGDs result in the doubling of the entire genome, providing raw genetic material that can lead to the development of novel traits and adaptations. This process is crucial for the acquisition of evolutionary novelties, which are essential for adapting to new environments and invading new ecological niches (Moriyama and Koshiba-Takeuchi, 2018). The retention of duplicated genes following WGD can facilitate phenotypic evolution, allowing legumes to develop unique traits that contribute to their diversification (Ren et al., 2018; Landis et al., 2018). For instance, the preferential retention of genes involved in essential cellular metabolisms post-WGD has been linked to the promotion of angiosperm radiation and enhanced adaptation to environmental changes (Ren et al., 2018).
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