| The sect.Tuberculata,belonging to the genus Camellia L.,comprises 18 species,all of which are endemic to China.They are primarily distributed in Guizhou,with an expanded range in the southwestern and adjacent central provinces,forming a distinct distribution area.These plants predominantly grow in limestone areas and exhibit strong regional characteristics.Previous classifications of this plant group primarily relied on macroscopic characteristics,supplemented by insufficient field investigations,resulting in a series of fundamental taxonomic issues.These issues include synonymous names,questionable nomenclature,ambiguous species boundaries,and unknown inter-species relationships,posing significant challenges to the conservation and utilization of the germplasm resources of the sect.Tuberculata.Therefore,based on comprehensive field investigations,this study conducted macroscopic morphological studies,leaf epidermal micro-morphological studies,and pollen micro-morphological studies of 13 species of sect.Tuberculata,as well as the taxonomically disputed Camellia ilicifolia,which is related to Camellia neriifolia,and constructed a chloroplast genome(cp DNA)-based phylogenetic tree to provide new evidence for the classification of these plants and clarify the complex inter-species relationships within this group.Additionally,this research conducted a preliminary study on the ornamental value of these plants,aiming to provide scientific support for future economic development potentials.The main findings of this study are as follows:(1)All of these 13 species of the sect.Tuberculata and the disputed Camellia ilicifolia exhibit a narrow geographic distribution.They are narrowly distributed,occurring in small populations in karst mountains or river valleys with variations in their habitats.(1)Macroscopic morphology: Significant differences were observed in flower color,fruit morphology,and leaf characteristics among these plants.These macroscopic traits can serve as primary characteristics for classification.Furthermore,the color and texture of the main trunk bark exhibited significant differences among species,providing an additional basis for inter-species classification.This morphological trait is a novel characteristic not identified by previous researchers.(2)Leaf epidermal micro-morphology: The upper and lower leaf epidermis exhibited distinct differences in the periclinal wall patterns,primarily showing wavy patterns followed by shallow wavy patterns.Stomata were mainly elliptical in shape,and oil glands were primarily distributed on the upper and lower leaf epidermis of six species,including Camellia zengii F.A.Zeng,Camellia rhytidocarpa Chang et Liang,and Camellia rhytidophylla Li et Yang.Stable differences were observed in leaf epidermal cell morphology,periclinal wall patterns,stomatal morphology,and closure degree,which can serve as identification criteria for certain species within the group.(3)Pollen morphology: The pollen grains were classified as medium-sized,mainly exhibiting flattened spherical shapes with distinct variations in exine ornamentation.The outer exine ornamentation appeared as wrinkled grooves,wrinkled waves,wrinkled wave-like granules,or granules.These pollen micro-morphological features can be used as one of the criteria for inter-species classification.(4)Based on the construction of a phylogenetic tree using chloroplast genomes,it is indicated that the 13 species in the Sect.Tuberculata and Camellia ilicifolia together form a clade(ML= 100%(BS),BI = 1.0(PP)).This suggests that this group is a monophyletic clade,and Camellia ilicifolia should be classified within the sect.Tuberculata.Camellia anlungensis,Camellia leyeensis,Camellia pyxidiacea,and Camellia rubituberculata collectively form another clade(ML = 99%(BS),BI = 1.0(PP)).Among them,Camellia anlungensis and Camellia leyeensis form a separate clade(ML = 100%(BS),BI = 1.0(PP)),indicating their close phylogenetic relationship.Camellia rubituberculata and Camellia pyxidiacea do not share a clade,indicating that they are not variants of each other.(2)Based on comprehensive studies of macroscopic morphology,leaves epidermal micromorphology,pollen micromorphology,chloroplast genome phylogenetic trees,and geographic distribution characteristics,the following preliminary revisions in the classification of some species are proposed:(1)Camellia leyeensis should be treated as Camellia anlungensis;(2)Camellia neriifolia and Camellia ilicifolia should regain their status as independent species,with Camellia ilicifolia being classified within the section Sect.Tuberculata;(3)Camellia rubimuricata should be considered a white-flowered type rather than a red-flowered type,thus revising its name to Camellia albaflora within the Sect.Tuberculata section,and Camellia zengii and Camellia rubimuricata should regain their positions as independent species;(4)Camellia pyxidiacea and Camellia rubituberculata do not represent variant relationships but should be treated as independent species;Camellia acutiperulata should be reinstated as a separate species.Furthermore,during the investigation in Chishui,Guizhou,a previously unrecorded species in the Tuberculata was discovered(Camellia chishuiensis Z Li & X Xiao,sp.nov.)(provisional name).The main morphological differences of this species compared to others are: white flowers,capsule-shaped fruits with a deep concavity in the center resembling a gourd,and elongated or narrowly elliptic leaves with numerous oil glands on the upper surface.(3)By conducting an Analytic Hierarchy Process(AHP)analysis on the aesthetic value of 14 plants,the results demonstrate that these plants can be categorized into three classes based on their development and utilization potential.Class I(≥4.0)includes three species with extremely high aesthetic value,which can be prioritized for development and utilization.Class II(3.0-4.0)comprises eight species with high aesthetic value,suitable for appropriate development.Class III(≤3.0)consists of two species with average aesthetic value,which can be developed on a smaller scale or temporarily not utilized. |
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