Journal of Tea Science Research, 2024, Vol.14, No.1, 64-78 http://hortherbpublisher.com/index.php/jtsr 65 understanding the evolutionary history of Camellia plants. By analyzing genomic data, researchers can uncover the genetic basis of important traits, such as stress resistance, secondary metabolite production, and adaptation to different environments (Zhang et al., 2021; Wu et al., 2022; Cheng et al., 2022). Whole-genome sequencing, transcriptomic analyses, and chloroplast genome studies have provided valuable insights into the phylogenetic relationships and evolutionary dynamics within the genus (Wei et al., 2018; Li et al., 2021; Cheng et al., 2022). These studies have revealed significant events such as whole-genome duplications and introgressions, which have contributed to the genetic diversity and adaptation of Camellia species (Wei et al., 2018; Li et al., 2021; Cheng et al., 2022). The primary objective of this study is to synthesize current genomic research to elucidate the evolutionary history of the Camellia genus. By summarizing recent genomic research findings, we aim to provide a comprehensive understanding of the phylogenetic relationships, speciation events, and adaptive evolution within the Camellia genus. Identifying key evolutionary events, including highlighting significant genomic events such as whole-genome duplications, introgressions, and selection pressures that have shaped the evolution of Camellia species. Promoting future research and breeding programs, laying a foundation for future studies on the functional and morphological evolution of Camellia. By achieving these goals, we hope to gain a better understanding of the evolutionary history of Camellia plants and enhance their conservation and utilization in agriculture and horticulture. 1 Literature Review and Theoretical Framework 1.1 Classification and grading of the genus Camellia The genus Camellia, belonging to the family Theaceae, comprises over 200 species, making it the largest and most significant genus within this family (Li et al., 2019). The classification of Camellia species has been challenging due to frequent interspecific hybridization and polyploidization, which complicate phylogenetic and taxonomic resolutions (Huang et al., 2013; Li et al., 2019). Recent advances in chloroplast genome sequencing have provided new insights into the phylogenetic relationships among Camellia species, aiding in more accurate classification (Huang et al., 2013; Yang et al., 2013; Li et al., 2019). Among the major species within the genus, Camellia sinensis, Camellia japonica, and Camellia sasanqua are the most well-known. The distribution and diversity of these species are influenced by their evolutionary history and environmental adaptations (Huang et al., 2013; Wu et al., 2022). Camellia sinensis is widely cultivated in subtropical and tropical regions across Asia, particularly in China, India, and Sri Lanka, due to its significance in tea production. Camellia japonica and Camellia sasanqua are predominantly found in Japan and China, where they are highly valued as ornamental plants. Other notable species, such as Camellia oleifera, known for its oil-rich seeds, are distributed in various parts of East Asia (Yang et al., 2013; Li et al., 2019; Wu et al., 2022). 1.2 Morphological and ecological characteristics of Camelliagenus Camellia species exhibit a wide range of morphological traits, including variations in leaf shape, flower color, and seed structure. These traits not only aid in species identification but also reflect their adaptation to different ecological environments. Studies have found that Camellia sinensis typically has small, leathery leaves and white flowers, whereas Camellia japonica is known for its large, glossy leaves and a variety of flower colors, including red, pink, and white (Majumder et al., 2020). These morphological differences are often used to distinguish between species and are supported by genetic studies (Huang et al., 2013; Yang et al., 2013; Wu et al., 2022). For instance, chloroplast genome analysis has revealed specific genetic markers associated with morphological traits, aiding in species identification and classification (Li et al., 2019; Lin et al., 2022). Camellia species occupy diverse ecological niches, ranging from subtropical forests to mountainous regions (Wu et al., 2022). Camellia sinensis thrives in humid, subtropical climates with well-drained soils, often found in regions with ample rainfall and moderate temperatures. In contrast, Camellia japonica prefers cooler, temperate climates and is commonly found in shaded woodland areas (Majumder et al., 2020). Camellia sasanqua, known for its ability to withstand drought and poorer soil conditions, often occupies more challenging habitats compared to its counterparts.
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