Table of Contents

18 July 2011, Volume 49 Issue 4
Cover illustration: Inflorescences of five chloranthaceous species. A, Sarcandra hainanensis. B, Chloranthus spicatus. C, Chloranthus serratus. D, Chloranthus sessilifolius. E, Chloranthus angustifolius. Photographed by Hong-Zhi KONG. See ZHANG et al., pp. 315–329 in this issue.
    Research Articles
  • Ongkarn VANIJAJIVA, Joachim W. KADEREIT
    J Syst Evol. 2011, 49(4): 285-314.
    A revision of the paleotropical genus Gynura Cass. is presented. Forty-four species are recognized, of which three are described as new. These are G. daviesiae Vanijajiva & Kadereit, G. villosa Vanijajiva & Kadereit, and G. siamensis Vanijajiva & Kadereit. Gynura dissecta (F. G. Davies) Vanijajiva & Kadereit, G. annua (F. G. Davies) Vanijajiva & Kadereit, and G. aurantiaca (Bl.) DC. subsp. parviflora (F. G. Davies) Vanijajiva & Kadereit are new combinations. An identification key, descriptions, and distribution maps are provided.
  • Qiang ZHANG,Alexandre ANTONELLI,Taylor S. FEILD,Hong-Zhi KONG
    J Syst Evol. 2011, 49(4): 315-329.
    Chloranthaceae is one of the earliest diverging angiosperm families and is comprised of approximately 75 species in four genera (Chloranthus, Sarcandra, Ascarina, and Hedyosmum). This family has received considerable attention because of its seemingly primitive morphology, disjunct tropical distribution in Asia and America, and extensive fossil record from the Early Cretaceous. In the present study, we reconstructed the phylogeny of Chloranthaceae based on a combined dataset of three plastid DNA regions and 56 species. We then estimated divergence times in the family using two relaxed molecular clock methods (BEAST and penalized likelihood). We focused on testing the influence of fossil taxa in calibrating the molecular phylogeny, and on assessing the current taxonomy of the family in light of the phylogenetic results. Our results indicate that most intrageneric divisions within Ascarina and Hedyosmum are not monophyletic. The results from the dating analysis suggest that the Hedyosmum-like fossil Asteropollis represents a stem lineage of Hedyosmum, as has been suggested previously from morphological analyses. In contrast, our results indicate that the Chloranthus-like fossil Chloranthistemon, previously suggested on morphological grounds to be a stem relative of Chloranthus, may, instead, belong to the branch leading to the clade Chloranthus+Sarcandra. The median crown ages of Chloranthus, Sarcandra, Ascarina, and Hedyosmum estimated in the BEAST analysis were 26.3, 9.5, 31.0 and 45.8 million years ago (Ma), respectively, whereas the divergence between Chloranthus and Sarcandra, the splitting of Ascarina with the former two genera, and Hedyosmum separating from the three genera were estimated to 63.8, 95.7 and 111.1 Ma. The present study sheds further light on the temporal evolution of Chloranthaceae and exemplifies how molecular dating analyses may be used to explore alternative phylogenetic placements of fossil taxa.
  • Jian-Hua FAN, Leonard B. THIEN,Yi-Bo LUO
    J Syst Evol. 2011, 49(4): 330-338.
    This study analyses the pollination systems and biogeography of three allopatric species of Schisandra (Section Euschisandra) consisting of S. glabra (North America), S. bicolor (China), and S. repanda (Japan); the clade is delimited in a phylogenetic tree of Schisandraceae constructed with nuclear and plastid genes. The male and female flowers of these species have similar floral structures, but exhibit different pollination systems. At the base of the clade, S. glabra is pollinated by a wide variety of beetles and flies in a generalist pollination system that also includes floral heat and the use of male and female flowers as brood sites for insects. In Asia, however, S. bicolor and S. repanda are pollinated exclusively by one or two different species of gall midges (Resseliella spp.) in a specialist pollination system. In this system only female, pollen-eating gall midges pollinate the flowers and breed on nearby spiderwebs. The gall midge pollination system is specialized and derived from the generalist system in S. glabra, and basal in the clade. Pollen is the main floral resource, and we hypothesize it is exploited to enrich eggs, and as a result species of gall midges could increase reproductive fitness by feeding on a single dependable food source. Subsequently the life cycles of the plants and insects evolved into a tight association in old stable plant communities in the Sino-Japanese flora. Divergence times for the plant species are presented and correlated with past distributions and migration routes.
  • Tao DENG, Ying MENG, Hang SUN, Ze-Long NIE
    J Syst Evol. 2011, 49(4): 339-346.
    Chaetoseris and Stenoseris are two morphologically close genera from the tribe Cichorieae of the sunflower family and they are endemic in alpine eastern Himalayas to the Hengduan Mountains of SW China. Mitotic chromosome numbers and karyotypes are reported for 12 populations representing eight species of Chaetoseris and two species of Stenoseris from the Hengduan Mountains region. Eight species are new and the other two provide confirmation of previous reference. All Chaetoseris and Stenoseris taxa are diploidy with 2n= 16 and their basic number is tentatively suggested as x= 8. Karyotypes of Chaetoseris and Stenoseris are similar to each other with 2A and 2B for the former and 2A for the latter. Cytological data of chromosomal numbers and karyotypes support a close relationship of the two genera. Currently no polyploids are found for these two genera and it seems that polyploidization has played a minor role in their evolutionary speciation in the Hengduan Mountains region.
  • Quan-Wen DOU, Tong-Lin ZHANG, Hisashi TSUJIMOTO
    J Syst Evol. 2011, 49(4): 347-352.
    Genome constitution and genetic relationships between six Elymus species were assessed by physical mapping of different repetitive sequences using a technique of sequential fluorescence in situ hybridization and genomic in situ hybridization. The six Elymus species are all naturally growing species in northwest China, namely, E. sibiricus, E. nutans, E. barystachyus, E. xiningensis, E. excelsus, and E. dahuricus. An StStHH genome constitution was revealed for E. sibiricus and StStHHYY for the remainder species. Each chromosome could be clearly characterized by physical mapping with 18S-26S rDNA, 5S rDNA, Afa-family, and AAG repeats, and be allocated to a certain genome by genomic in situ hybridization. Two 5S rDNA sites, each in the H and St genomes, and three 18S-26S rDNA sites, two in the St genome and one in the Y genome, were uncovered in most of the species. The strong Afa-family hybridization signals discriminated the H genome from the St and Y genomes. The H and Y genome carried more AAG repeats than St. A common non-Robertsonian reciprocal translocation between the H and Y genomes was revealed in E. barystachyus, E. xiningensis, E. excelsus and E. dahuricus. Comparison of molecular karyotypes strongly suggests that they can be classified into three groups, namely, E. sibiricus, E. nutans, and others.
  • Li WANG,Di WANG,Ming-Ming LIN,Yan LU,Xiao-Xue JIANG,Biao JIN
    J Syst Evol. 2011, 49(4): 353-361.
    Ginkgo biloba L. is considered one of the most ancient seed plants, with several primitive features of plant reproductive process. However, the phylogenetic position of Ginkgo and its relationship with other extant seed plants remain unclear. To gain a better understanding of these issues, we observed the embryological development of G. biloba using semi-thin sections and scanning electron microscopy. In late August, the zygote moved from the end of the micropylar to the middle of the archegonium, and mitosis resulted in many free nuclei distributed randomly in the archegonium. Afterwards, the cell wall was formed and the proembryo began to differentiate into the embryonal region and the underdeveloped presuspensor region. In early October, the embryo differentiated into two cotyledons, plumule, hypocotyl, radicle, and suspensor tissues. Subsequently, the two cotyledons grew rapidly, but the undeveloped suspensor began to degenerate and gradually disappear, indicating that the embryo had begun to mature. During early embryo development, the main supply of nutrients was carbohydrate in the cells of the jacket, tentpole, and surrounding endosperm, whereas endosperm provided nutrients during embryo maturation. Our results indicate that Ginkgo is extremely similar to cycads in terms of embryology but more similar to conifers in macromorphology and vegetative anatomy, suggesting that the Ginkgo lineage may have an intermediate phylogenetic position between cycads and conifers.
  • Nasr M. HASSAN
    J Syst Evol. 2011, 49(4): 362-371.
    The pollen morphology of 11 species (including two subspecies and two varieties) belonging to two genera (Helianthemum and Fumana) of the family Cistaceae in Egypt was studied using light and scanning electron microscopy. Pollen grains of the studied taxa were found to be radially symmetrical and tricolporate. Pollen size, shape, apertures, and exine ornamentation characteristics were valuable parameters among the studied taxa. The largest pollen size was recorded in H. salicifolium and the smallest one observed in H. kahiricum subsp. schweinfurthii. Pollen shape in the Egyptian taxa varied from (sub-)prolate to prolate spheroidal, but F. arabica is different in having sub-oblate grains. The pollen data confirm that H. lippii and H. sessiliflorum are very closely related species. Pollen sculpture was useful in distinguishing between H. vesicarium var. vesicarium and H. vesicarium var. ciliatum. Three main pollen types of exine ornamentation were recognized: retipilate; reticulate to verrucate; and striate. Based on palynological data, a key for the studied taxa is suggested.
  • Hong-He XU, Yi WANG
    J Syst Evol. 2011, 49(4): 372-378.
    According to newly collected and well preserved specimens, herbaceous lycopsids Colpodexylon gracilentum Dou and Colpodexylon laminatum Dou from the late Middle Devonian of Xinjiang, NW China are reduced to C. gracilentum, for which a neotype is designated and emended diagnosis is given. Colpodexylon gracilentum has leaves with three nearly equal segments, an elliptical sporangium adaxially attached by a pad on the isomorphic sporophyll.