Table of Contents

18 September 2005, Volume 43 Issue 5
    Research Articles
  • Qin-Er YANG
    J Syst Evol. 2005, 43(5): 389-389.
  • LI Yong
    J Syst Evol. 2005, 43(5): 390-391.
  • WANG Wen-Tsai
    J Syst Evol. 2005, 43(5): 398-402.
  • TANG Yan-Cheng, LU An-Ming
    J Syst Evol. 2005, 43(5): 403-419.
    In this essay, three currently hotly debated issues in biological systematics, i.e., the paraphyletic group, the PhyloCode, and the phylogenetic species concept, have been briefly reviewed. (1) It is widely acknowledged that cladistics has made some positive contributions to the study of systematics. In particular, the employment of outgroup analysis for assessing character polarities, the application of synapomorphies to the inference of relationships between taxa, and the use of cladistic methods for reconstructing phylogeny, have all greatly facilitated the improvement of systematic approaches. A fatal flaw in cladistics is its refusal to accept paraphyletic groups. Frankly, we are adherents and practitioners of phyletics, and hence consider paraphyletic groups to be acceptable. For example, an AFLP analysis has shown that Zabelia (Caprifoliaceae) can be included in Abelia, but the members in Zabelia differ from those in Abelia not only in pollen morphology, but also in having persistent petioles dilated and connate at base, thus enclosing axillary buds, characters of adaptive significance obtained possibly when Zabelia members entered a new ecological niche, so we consider that they are better treated as two independent genera, though indeed such a treatment makes Abelia paraphyletic. (2) Some cladists pointed out that as the tool for communication and the system for information storage and retrieval, biological nomenclature is required to be unambiguous, unique and stable. They criticise the Linnaean rank-based system of nomenclature for failing to satisfy such requirements for the naming of clades and species. To address this problem, the PhyloCode is proposed in recent years, in which three definitions for clade naming are given, i.e., the node-based, the stem-based, and the apomorphy-based. We are of the opinion that since the Linnaean binominal system of botanical nomenclature has existed for nearly 250 years, the rejection of this system and the adoption of the PhyloCode would create a state of chaos in botanical nomenclature. This does not mean that there exist no merits in the proposals made by the PhyloCode supporters. We suggest that further studies should be conducted for its practical application. (3) It has been well known that there are many problems with the application of the biological species concept in plants, and thus at the present time the majority of plant systematists actually seldom use this concept in their practical work. The rapid development of cladistic approach has motivated the proposal of the phylogenetic species concept. This species concept is established based on three criteria, i.e., the autamorphy, the diagnosability and the basal exclusivity, hence the autamorphy species concept, the diagnosability species concept, and the genealogical concept are created respectively. Nevertheless, the morpho-geographical species concept is still predominantly adopted in plant systematics. When using this species concept, however, we should also take into account the data from other sources, particularly those from pollination biology, breeding system and molecular systematics.
  • LU An-Ming, TANG Yan-Cheng
    J Syst Evol. 2005, 43(5): 420-430.
    In this paper, some viewpoints on the origin of angiosperms are discussed. (1) The angiosperms share certain remarkably consistent character syndrome, and thus it is unlikely that they evolved from more than one ancestor, although they might have a common ancestor group. The angiosperms should be a group of unitary origin. The classification systems of extant angiosperms were constructed based on comprehensive evidence from morphological, molecular systematics, palaeobotanical, and phytogeographical studies, and could only express affinity among the extant angiosperms. At present it is impossible to construct a phylogenetic system that contains all extinct and extant angiosperm groups, and for this reason the classification systems of extant angiosperms can only be considered as “affinity” ones. (2) The evidence from molecular clocks, fossils and geographic distribution data on the origin time of angiosperms has been greatly accumulated in the past two decades. Fossil data are very important for determination of the origin time of angiosperms. However, fossil evidence is only the integrated embodiment for the preserved parts of plants and geological fossilization conditions, but is not, and unlikely to be, the indicator of the exact age of the groups or species. In addition, we have to consider the evolutionary history of the fossils. The application of molecular clocks is another approach, but it carries even greater errors. Besides the two lines of evidence, researches on modern distribution patterns, the formation of the plant groups, and combination of plant evolution with the earth history as well as the theory of plate tectonics, can undoubtedly improve the reliability in inferring angiosperm origin time. Analyses of 56 important spermatophyte (mostly angiosperms) families or genera at different evolutionary levels have suggested that the origin time of angiosperms could be dated back to the Early Jurassic or Late Triassic. (3) The nature of basal angiosperm groups, i.e., members of ANITA grade (incl. Amborellaceae, Nymphaeaceae, Illiciales, Trimeniaceae and Austrobaileyaceae), is analyzed. Views on the systematic positions of ANITA members in modern classification systems of angiosperms are discussed, and their morphological characters (sensu lato) are evaluated. We consider that the ANITA members belong to the primitive groups because of their many plesiomorphies. But they only share few synapomorphies, such as globose pollen grains, indicating that they may have already diverged into different lineages during the early stages of angiosperm evolution. Therefore, ANITA is a complex group originated from different lineages.
  • WANG Wen-Tsai, LI Liang-Qian
    J Syst Evol. 2005, 43(5): 431-488.
    A new system of classification of the genus Clematis is proposed. The taxonomic history of the genus is briefly reviewed. On the basis of the analyses of various morphological and palynological characters, evolutionary trends of some characters are revealed as follows: 2. Seed germination: epigeal→hypogeal. 3. Leaf: (a) phyllotaxy: alternate→opposite→verticillate. (c) texture: herbaceous→papery→subcoriaceous or coriaceous. 4. Inflorescence: (a) position: terminal→terminal and axillary→axillary. (b) type: pedunculate, bibracteate, several-flowered cyme. (i) 3–4 times branched, 20–35-flowered cyme→many-branched ca. 100-flowered panicle. (ii) 1-flowered cyme→a single flower, pedicellate, but with peduncle and bracts wanting. 5. Flower: (a) Sexuality: bisexual→unisexual. (b) Posture: erect, with straight pedicel→pendulous, with recurved pedicel. 6. Sepal: (a) number per flower: 4 or 5→6–8. (b) aestivation: valvate→imbricate. (c) colour: white or yellow→blue, purple or red. (d) spreading direction: spreading→ascending→erect. (e) texture: herbaceous or papery→subcoriaceous or coriaceous. (f) shape: obovate→obovate-oblong, oblanceolate, lanceolate or oblong→narrowly oblong→linear. (g) apex: rounded or obtuse→acute→acuminate→attenuate (h) margin indumentum: glabrous or puberulous→with a narrow velutinous strip. (i) margin dilation: not dilated→dilated. (j) indumentum of adaxial surface: glabrous→puberulous→velutinous. 7. Stamen: (a) indumentum: glabrous→filament hairy yet anther glabrous→both filament and anther hairy. (b) filament: (i) linear→proximally or distally widened, or entirely so. (ii) flat→rugose. (c) anther: oblong, 0.8–3.5 mm long→narrowly oblong, 2–6 mm long→linear, up to 7–10 mm long. (d) connective: not projected→apex minutely apiculate, with an apiculum ca. 0.1 mm long→apex with a conic or subglobose projection 0.1–0.2 mm long→apex with a subulate projection up to 4 mm long or with a narrowly lamellate projection 1–10 mm long. 9. Staminode: (a) absent in bisexual flower→present in bisexual flower. (b) number per pistillate flower: numerous→few→zero. 10. Style: not elongate→elongate and plumose→slightly elongate and appressed-puberulous, then tail-like or subulate in shape→very short, slightly or not elongate, appressed- puberulous or glabrous. 11. Fruit: not complanate, nor rimmed, nor marginate→complanate, narrowly to tumidly rimmed→complanate, broadly marginate or winged. According to the evolutionary trends mentioned above and mainly according to the floral structure, the relationships among the 15 sections of Clematis are discussed, and four evolutionary stocks are recognized. Of them, the C. montana stock, in which C. brevipes, C. potaninii, C. montana etc., all with spreading, white, obovate sepals and glabrous stamens, are included, is regarded as the primitive group of the genus, whereas the other three, C. vitalba stock, C. connata stock, and C. alpina stock, are regarded as more advanced. All these four stocks might be derived from a putative extinct primitive group of the genus, which might possess the most primitive vegetative and reproductive characters. The four stocks are all treated as subgenera in the present system. Finally, a systematic enumeration of all the infrageneric taxa is presented and their brief diagnoses are given.