Taxonomic Study On The Genus Rhaphiolepis (Rosaceae)

Rhaphiolepis Lindl., a small genus of Maloideae (Rosaceae), currently contains about15species in the world, which distributed in East and Southeast Asia. Although it is not a large genus, about half of species within the genus are still not well revoled, which had not yet been well treated for even one time in the worldwide scale. Based on the evidence of morphology, the micromorphology of leaf epidermis, pollen morphology and molecular systematics, the taxonomic revision of Rhaphiolepis is performed in this study for the first time.Leaf epidermis of8species of Rhaphiolepis were investigated under both light microscope and scanning electron microscope. Accordding to the characters of upper epidermis, the genus is divided into three types. The first one is polygonal cells with straight anticlinal walls, the second is polygonal cells with straight to arched anticlinal walls, the third is irregular cells with repand or sinuous anticlinal walls. The sculpture of lower epidermis can be devided as three types, apophysis, wrinkle ridge and stripes to apophysis. The stomas, containing a variety of types, are irregularly arranged on the lower surface of leaves. The shape, size and the character of outer stomatal rims of the stomas exhibit interspecific variation. In a word, the micromorphological characteristics of the leaf epidermis have taxonomic significance at specicies level.Pollen grains of7species of Rhaphiolepis were examined by light microscope and scanning electron microscope. All species in Rhaphiolepis are with tricolporate pollen grains. The shape of the pollen grains vary from subspheroidal to prolate. Sculptural types of Rhaphiolepis were observered as reticulate, striate-foveolate and striate. The patterns of pollen sculpture may have significance in solving the problems such as evolution and classification of Rhaphiolepis.Molecular phylogenetic analyses constructed by three chloroplast DNA regions (matK、psbA-trnH and trnL-F) revealed that:Rhaphiolepis is a monophyletic. However, interspecific relationship is not well resolved with fewer informative sites.Based on extensive literature survey, specimen examination, field observations and experimental evidence,12species and3variations in Rhaphiolepis wordwide have been accepted. The status of Rhaphiolepis indica var. mekongensis Cardot is reconfirmed. Rhaphiolepis integerrima Hook.&Arn. and Rhaphiolepis umbellata var. minor Makino are treated as synomyms of Rhaphiolepis umbellata (Thunb.) Makino, Rhaphiolepis parvibracteolata Merr. and Rhaphiolepis indica var. latifolia Cardot aretreated as synomyms of Rhaphiolepis indica var. mekongensis Cardot. Lectotypes of six taxa, Rhaphiolepis gracilis Nakai, Rhaphiolepis indica var. mekongensis Cardot, Rhaphiolepis indica var. latifolia Cardot, Rhaphiolepis hainanensis Metcalf, Rhaphiolepis ferruginea Metcalf and Eriobotrya philippinensis Vidal, are confirmed in this study.