Ge Song, B. A. Schaal, Hong De-yuan
1997, 35 (5): 385-395.
Adenophora Fisch. (Campanulaceae)is a medium-sized and diverse genus, which occurs mainly in eastern Asia, particularly in China. Although several taxonomic systems have been proposed, there is still much debate on the delimitation and systematic arrangement of the species within the genus, due mainly to high variation in morphology, habitats, phenotypic plasticity, and potential hybridization. A. lobophylla Hong is a rare perennial endemic to several counties of Sichuan, China. Since this species was recognized, much work has been done on its taxonomic status, including morphology, crossing experiment and allozymes. However, evidence available is not concordance so far, and its relationship with other species within the genus remains largely uncertain. In the present paper, the internal transcribed spacer(ITS) region of 18s～26s nuclear ribosomal DNA was sequenced in 10 representatives of Adenophora and two outgroup species of Campanula to assess its utility for phylogenetic reconstruction in Adenophora, in addition to reevaluation of the taxonomic status of A. lobophylla. The results indicate that there exist high sequence alignability and length conservation among ITS sequences, with informative sites being 3.9% and length ranging from 539 to 541 bp and G + C content varying from 57% to 60%. Phylogenetic analyses using Fitch parsimony show that A. lobophylla is closely related to A. himalayana instead of A. potaninii or A. stenanthina as revealed by previous morphological work and crossing experiment. The ITS phylogeny is generally congruent with other evidence in that A. lobophylla should be removed from the A. potaninii complex or even subsect. Microdiscus. Its appropriate placement, however, should be further explored. In pairwise comparisons at unambiguously aligned sites, sequence divergence was relatively low among Adenophora species with the values ranging from 0.0 to 3.9% in spite of the fact that the species surveyed covered all of the sections and subsections of the genus. In contrast, high sequence divergence is found among Adenophora and Campanula species with the values from 17.8 % to 19.2 %. The low divergence among Adenophora species is justified considering its recent origin, and also suggests that ITS sequence would provide a promising source of nuclear phylogenetic markers to reconstruct the phylogeny within Campanulaceae on the tribe and family levels.
Krishna K. Shrestha
1997, 35 (5): 396-433.
Cyananthus Wallich ex Bentham, the only genus of Campanulaceae with superior ovary, is revised to clarify infrageneric relationships and phylogeny of the genus. Evidence obtained from the comparative gross morphology, anatomy, palynology, and karyomorphology recommends a new infrageneric classification of the genus, recognizing 23 species, belonging to two subgenera, four sections and four subsections. One subgenus(Subgen. Micranthus), one section(Sect. Suffruticulosi) and two subsections(Subsect. Flavi and Subsect. Lichiangenses)are described as new taxa. New combinations at sectional(Sect. Annui) and subsectional(Subsect. Stenolobi) ranks are also proposed. The genus Cyananthus is strictly distributed in the high mountains of China(Xizang, Yunnan and Sichuan), extending to Bhutan, Nepal and India(Kumaon-Garhwal, Assam and Sikkim), with altitudinal ranges from 2500～5300 m. It is observed that 13 species are endemic to SW China and only three species are endemic to the Himalayas(two species in Nepal and one to NW India). It is evident that Cyananthus is one of the most primitive genera of Campanulaceae and within the genus, subgenus Cyananthus(Sect. Stenolobi) is more primitive than the subgenus Micranthus. It is also suggested that SW China(most probably Yunnan) is the center of origin of Cyananthus, considering the occurrence of as many as 20 species of Cyananthus, representing several primitive taxa and many endemic species.
Shang Zong-yan, Li Ru-juan, Cui Tie-cheng, Xu Jie-mei
1997, 35 (5): 434-444.
Chromosomes of 14 populations of 8 species of Allium from China were observed
in the present work. The results are as follows: (1)A. tuberosum Rottl. ex Spreng: three
populations were studied and they were all tetraploids (2n=4x=32) with 28 m and 4 st on
which satellites usually appeared. The population 1 (C-1237) was found to have the karyotype 2n=4x=32=28m+4st(2SAT) (Fig. 1:1 ), the population 2(C-1188) 2n=4x=32=
28m+4st (4SAT) (Fig. 1: 2), and the population 3 (C-1179) with satellites ranging from one to three in number. In some cells we found that the satellites look like a string of beads (Fig.1: 3). (2) A. ramosum L.: the population 1 (C-1193) was diploid with the karyotype 2n =2x = 16 = 14m + 2st ( 2SAT ) ( Fig. 2: 2), while the population 2 (C-1307) was tetraploid with 2n=4x = 32 (Fig. 2:5). The number of sat-chromosomes ranged from zero to three. (3)
A. anisopodium Ledeb.: the population 1 (C-1313) was found to have the karyotype 2n=2x
=16=12m+ 4sm(2SAT) with a pair of terminal satellites ( Fig. 2:1), and the population 2 (C-1286) 2n=2x=16, with the satellite chromosomes exhibiting polymorphism (Fig 5). In
about 80% of cells, a chromosome was found to have a intercalary satellite, and thus the
karyotype became 2n=2x=16=14m+2sm(1SAT) (Fig. 2: 3). (4) A. anisopodium Ledeb. var. zimrmermannianum (Gilg) Wang et Tang (C-1253) was a diploid with 2n=2x=16. One pair of chromosomes had intercalary satellites, which were often detached from the chromosomes (Fig. 2:4). (5) A. nutans L. (C-1312) showed great intrapopulational variation in chromosome number. 2n= 4x=32, 2n=6x=48, 2n=8x=64 and 2n=9x=72 were found in different plants from the same population (Fig. 3: 1, 2, 3). (6) A. macrostemon Bunge(C-1245) had the chromosome number of 2n=4x=32. The satellite chromosomes exhibited polymorphism (Fig.2:6. Fig.5). (7) A. tubifiorum Rendle.: the population 1 (C-1279) was a diploid of 2n=2x= 16 with a pair of chromosomes with terminal satellites ( Fig. 3: 5), and the population 2 (C-1289) a tetraploid with 2n=4x=32,
with two pairs of chromosomes having terminal satellites(Fig. 3:4 ). (8) A. neriniflorum
(Herb.)Baker. The population 1 (C-1318) had the chromosome number of 2n=2x=16 with a pair of chromosomes having intercalary satellites. Non heterozygosity was found in this pair in 1991 (Fig.3: 6), but we found heterozygosity in 1992 (Fig. 3:7 ). The population 2 (C-1393) was also found to have 2n= 2x = 16. The heterozygous satellite chromosomes were found in a few root tips (Fig.3: 8. Fig.5).
Polyploidy is very common in Allium. Seven polyploid populations are reported in this
paper. Some species, such as A. ramosum and A. tubiflorum , had both diploid and tetraploid populations, while some others, such as A. nutans, had different plants respectively with 4x, 6x, 8x and 9x within populations.
We also found that in polyploids the number of satellite chromosomes was not always
correlated with ploidy level. Among the six tetraploids, two populations (C-1188, C-1289)
had four satellite chromosomes, two populations (C-1237, C-1245) had two and the other
two (C-1179, C-1307) had variable number (0～3) of satellites.
Fig. 1: 3 shows bead-like satellites on only one st chromosome among four in tetraploid
C-1179. It is supposed that the satellites of these three st chromosomes were transferred to that one and this“transfer”may lead to unstable number of satellites in polyploids.
Unlike number, the variation of satellite chromosomes in their morphology is more
closely correlated with external morphological characters. In the section Caloscordum, the
diploids of A. tubiflorum and A. neriniflorum have the same karyotype 2n = 2x = 16 =
12m + 4sm(2SAT), but there is a pair of chromosomes with terminal satellites in the former, while a pair of chromosomes with the intercalary satellites in the latter. Although they are quite similar, they are classified into two species. A similar situation is also found in A. anisopodium (C-1313 with a pair of chromosomes with terminal satellites) and its variety, var. zimmermannianum ( C-1253 with intercalary satellites); the latter has fine teeth on its scape. It is interesting to note that C-1286 seems to have fine teeth, as if this population is an intermediate type, and only one intercalary satellite chromosome is found in more than 80 % of cells. The morphological variation of satellite chromosomes might be one of possible causes leading to speciation.
We consider that the morphological variability and structural heterozygosity of satellitechromosomes are important sources of genetic variation and evolution in Allium.
Sun Kun, Wang Qing-feng, Chen Jia-kuan
1997, 35 (5): 445-451.
The importance of characters of seed coat for taxonomic and systematic research has begun to be appreciated in studies on the subclass Alismatidae recently. The present study examined micromorphological characters of seed coat of six genera, including 13 species, in the Hydrocharitaceae from China under scanning electron microscope. The characters are described and three types of seed coat are distinguished here according to cell shape of exotesta and endotegmen, sculpture of seed surface and endotegmen tuberculae: (1) Ottelia type, of which the seed coat sculpture is absent, ridged or pilose, cell of endotegmen is polygonal to nearly oblong, and tuberculae sparsely are granulate (e. g. Ottelia Pers. ); (2) Hydrocharis type, of which the seed coat sculpture is verrucate, cell of endotegmen is irregular, and tuberculae densely are baculate (e. g. Hydrocharis L. ); (3) Vallisneria type, of which the seed coat sculpture is verrucate, cell of endotegmen is oblong or nearly oblong, and tuberculae densely are tuberculate (e. g. Vallisneria L., Blyxa Thou et Rich., Nechamandra Planch., Hydrilla Rich. ). There are some differences between genera as well as species in characters such as cell shape of seed coat, sculpture of seed surface and endotegmen tuberculae, and these characters can be served as diagnostic ones for distinguishing tribes, genera and even species in this family. Micromorphology of seed coats supports Hutchinson’s (1959) and Eckhardt’s (1964) treatments about the tribes Ottelieae and Hydrochariteae. Vallisneria L., Blyxa Thou et Rich., and Nechamandra Planch. should be placed in the same tribe, and the genus Hydrilla Rich. is closely related to them. In addition, the similarity of verrucae on the seed surface as well as endotegmen tuberculae between the Hydrocharitaceae and Najadaceae may indicate that the two families are closely related.
Wang Qing-feng, Zhang Zhi-yun, Chen Jia-kuan
1997, 35 (5): 452-456.
Macromorphological and micromorphological characters of fruits in the genus Damasonium (Alismataceae), comprising five species, were examined by stereoscope and scanning electron microscope(SEM). We found that the fruits of this genus are usually follicles with 2～6 seeds, rarely achenes with a single seed, compressed, irregularly rectangular with long-beaks at apex, or triangulate with indistinct beaks, carpodermis covered by cuticlewhich is again covered densely with fragmentary or granulate waxy appendage. These characters, in authors’ opinions, are of some taxonomic significance in this genus. Combined with the other characters of this genus, we consider that the treatment of D. alisma and D. stellatum as two separate species is reasonable; D. californicum is still a member in the genus Damasonium, and D. polyspermum with some special characters is different from D. alisma. A key to the species of Damasonium is given in this paper. Stomata on the carpodermis in Damasonium, which are unique in the Alismataceae, are first reported.
1997, 35 (5): 457-460.
1997, 35 (5): 461-462.
Ji Meng-cheng, Wu Pan-cheng
1997, 35 (5): 463-464.
Wang Xiao-qun, Hong De-yuan
1997, 35 (5): 465-480.
Reviewed in the present paper are four most important factors stimulating the development of molecular systematics: improvement of molecular biological methods, complete sequencing of genome, recognition of evolution rules of increasing number of genes widely used in molecular systematics, and study of fossil DNA. Systematic importance of both nuclear genes and chloroplast genes is discussed. In addition, some exciting results in molecularphylogeny constructed from sequence analyses of rbcL, matK, 18s rDNA and ITS are enumerated respectively. Moreover, the authors put forward some problems needing attention in molecular systematic study.