| Enkianthus belongs to Ericaceae,with about 12-17 species.It is only distributed in East Asia.It is an important ornamental plant of Ericaceae and a dominant group of Subtropical topmountain dwarf forest.It has important ornamental and ecological values.However,there are still many problems in terms of classification and phylogeny within this genus.In this study,by integrating different lines of evidence from macromorphology,micromorphology of leaf epidermis,cytogenetics,molecular systematics and Biogeography,we addressed the following issues.A comprehensive field investigation was carried out on Enkianthus distributed in China.A total of 151 plant specimens,481 specimens and more than 2002 molecular samples were collected.Cluster analysis based on morphological data showed that,Enkianthus could be divided into three groups.(1)The first group features flowers in umbels,inflorescence and fruit upward;(2)The second is characterized by flowers in racemes or solitary,inflorescence downward,fruit upward,(3)The third possesses flowers in racemes,inflorescence and fruit downward.The epidermal cells of Enkianthus are polygonal and irregular,and the pattern of anticlinal walls are straight,curved and sinuous.The size of epidermis cells is about358.50～2740.01 μm2.Columnar multicellular hairs and single-cell Sharp hairs were found in the abaxial epidermis.The stomata are distributed in the abaxial epidermis,with anomocytic and paracytic shapes.The stomatal density is about 87.27 ～ 398.75 / mm2.The stomatal size is about 284.67～888.44 μm2.Based on the cluster analysis of 15 important leaf epidermal characters of 13 species of Enkianthus,can be divided into two groups.There are four different ploid levels in Enkianthus,i.e.,2x,4x,6x and 8x.The genome size of Enkianthus ranges from 683.87 Mbp to 3361.06 Mbp.The results of flow cytometry and chromosome tableting showed that t E.quinqueflorus,E.cernuus,E.quinqueflorus var.ciliatoserratus,E.serotinus,E.tubulatus,E.serrulatus and E.calophyllus are diploid(2n = 22);There are tetraploids and hexaploids in both E.deflexus and E.chinensis.E.ruber is tetraploid;The E.deflexus var.glabrescens is hexaploid;E.Campanulatus is octaploid.Based on the chloroplast genomsic sequences of 11 species of the genus,the relatively reliable phylogenetic tree of Enkianthus were constructed,which supports the division of the genus into three clades.After adding species and samples,the phylogenetic trees of 14 species of Enkianthus were constructed with 6 chloroplast fragments and nuclear genes ITS.It is found that the phylogenetic incongruence is very obvious.In addition,Enkianthus originated in the North American continent in the late Cretaceous(89.9 Ma)and differentiated into racemes and umbels in the Miocene(5.4 Ma).Combined with morphological,ploidy,molecular and other evidence,werecommend that the genus should be divided into three sections,namely,sect Enkianthus,sect.Enkianfella and sect Andromedina;In addition,this study put forward several taxonomic recommendations within Enkianthus: 1)the synonym treatment of E.calophyllus is incorrect and E.calophyllus should be treated as the synonym of E.perulatus.2)The status of E.quinqueflorus var.ciliatoserratus as a variety of E.quinqueflorus is recommended.3)The E.serotinus should be classified as a variety of E.serrulatus.4)E.tubulatus should be treated as a hybrid.5)E.ruber and E.deflexus.are treated as varieties of E.chinensis. |
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