A Taxonomical Study Of Caragana Fabr. From China

In this paper we mainly deal with the taxonomy of the genus Caragana Fabr.from China. At the basis of examining great amount of specimen materials from the majority of Chinese herbaria,and of field collecting in the desert area of Northwestern China,combined with some experimental methods,such as leaf anatomy,epidermal features of leaflet under LE and SEM, and karyological study of some species,we have reviewed the taxonomy and systematics of Chinese Caragana,in order to clarify some taxonomical and evolutionary problems existing in this genus.The main results are as follows:1.From 2003 to 2004 we carried out two expeditions over desert areas of Northwesten China,and collected more than 230 sheets of Caragana specimens which stand for 70 populations,and in identifying them we found one new species to science,C.qingheensis Z.Y. Chang,L.R.Xu & F.C.Shi.In the process of examining herbarium material,two more varieties have been discovered or combined,these are C.opulens Kom.var.angustifolia Y.Z. Zhao ex Z.Y.Chang & F.C.Shi and C.franchetiana Kom.var.crassispina(Marq.) Z.Y. Chang & F.C.Shi.C.pumila Pojark.and C.altaica(Kom.) Pojark.were also collected and identified from Northwestern China near border area with Kazakhstan for the first one and in desert area near Altai region for the second one,which had been overlooked by authors of "Flora of China"(Chinese version).Another 16 names were also reduced to synonyms in this paper.2.The leaflet anatomical structure in Caragana species seems to be results of long adaptation to its environment,which may be coupling with affinities.However,micromorphology of leaf epidermis was of taxonomic and systematic significance.The common epicuticular wax layer was thick and in the form of flakelets and the flakelets generally were digitate edged,or may be platelets in sometimes,or granules in sparse.The type of granule wax was mostly on abaxial surfaces,while thick flakelet wax occurred on both sides.More often the flakelet and the platelet waxes were together to form a thick layer.Most species in this genus were covered with hairs.Morphologically the hairs can be three types,cylindricalfiliform, which was slender and slightly sinuous,and cylindrical one,which was shorter than the former and straighter.The flattened ribbon-like hairs also occur,which were flat and lanceolate,straight or waved.On the surface of hairs,tow kinds of ornamentations often occurred,that is,striate,and striate with papillae,which may bear some evolutionary clues of the genus.The stomata were present on both surfaces in some species,but in others were seen only on the abaxial surface,except for C.bicolor and C.franchetiana,in which the stomata very interestingly occurred only on the adaxial surface.Only anomocytic stomata were seen in the genus,with outer stomatal rims smmoth or sinuous.and dentate.3.The karyotype of chromosomes in Caragana was not so much differentiated,and if differentiated it always followed by some morphological characters.The diploid and tetraploid are the main ploidy level of this genus,with 2n=16(diploid) or 2n=32(tetraploid).Triploid was found only in(sinica,and hexaploid was seen only in C.ussuriensis.Those species with diploid chromosomes mostly are pinnate-leaved,and mainly distributed in Estern Asia where probably being its ancestral area.but those species with tetraploid chromosomes are majorly with digitate leaflets,and more inclined to adaptive to desert areas in Northwestern China.4.As to the distributional pattern of Chinese Caragana,5 areal types could be grouped for the whole 64 species,namely Eastern Asian areal type,Mongolia-Xinjiang desert areal type, Qinghai-Xizang Plateau areal type,Middle Asia areal type and Disjunct areal type.Endemicity is also an important character for Caragana species,especially in China,nearly half of its total species are endemic.There are three endemicity centers for Chinese Caragana,i.e.Qinling Mt. and North China endemicity center,Qinghai-Xizang Plateau endemicity center and Mogolia-Xinjiang desert endemicity center.In Qinling Mr.and North China center,paleo-endemic species more often present,while in Mogolia-Xinjiang desert center,neo-endemic species more often occurred.In addition,vicarious distribution was common in the genus,and vicariance perhaps was very important in the speciation of the genus.5.According to the stomata distribution pattern,an adjusted scheme of infrageneric classification for Chinese Caragana was given,based mainly on Zhou Daowei(2005) and others,by occurrence of amphistomatic or hypostomatic leaf epidermis.Here 6 sections and 14 series were proposed for 64 species of Chinese Caragana.