Origin and phylogeny of Oryza species with the CD genome based on multiple-gene sequence data

The CD genome species in the genus Oryza are endemic to Latin America, including O. alta, O. grandiglumis and O. latifolia. Origins and phylogenetic relationship of these species have long been in dispute and are still ambiguous due to their homogeneous genome type, similar morphological characteristics and overlapping distribution. In the present study, we sequenced two chloroplast fragments (matK and trnL-trnF) and portions of three nuclear genes (Adh1, Adh2 and GPA1) from sixteen accessions representing seven species with the C, CD, and E genomes, as well as one G genome species as the outgroup. Phylogenetic analyses using parsimony and distance methods strongly supported that the CD genome originated from a single hybridization event, and that the C genome species (O. officinalis or O. rhizomatis instead of O. eichingeri) served as the maternal parent while the E genome species (O. australiensis) was the paternal donor during the formation of CD genome. In addition, the consistent phylogenetic relationships among the CCDD species indicated that significant divergence existed between O. latifolia and the other two (O. alta and O. grandiglumis), which corroborated the suggestion of treating the latter two as a single species or as taxa within species.We thank Tao Sang of Michigan State University (East Lansing, USA) and Bao-rong Lu of Fudan University (Shanghai, China) for their encouragement and assistance. We are also grateful to the International Rice Research Institute (Manila, Philippines) for providing plant material for this study. This research was supported by the Chinese Academy of Sciences (kscxz-sw-101A), the National Natural Science Foundation of China (30025005) and the Program for Key International S & T Cooperation Project of P. R. China (2001CB711103).     

Internal lipid synthesis and vesicle growth as a step toward self-reproduction of the minimal cell

One of the major properties of the semi-synthetic minimal cell, as a model for early living cells, is the ability to self-reproduce itself, and the reproduction of the boundary layer or vesicle compartment is part of this process. A minimal bio-molecular mechanism based on the activity of one single enzyme, the FAS-B (Fatty Acid Synthase) Type I enzyme from Brevibacterium ammoniagenes, is encapsulated in 1-palmitoyl-2oleoyl-sn-glycero-3-phosphatidylcholine (POPC) liposomes to control lipid synthesis. Consequently molecules of palmitic acid released from the FAS catalysis, within the internal lumen, move toward the membrane compartment and become incorporated into the phospholipid bilayer. As a result the vesicle membranes change in lipid composition and liposome growth can be monitored. Here we report the first experiments showing vesicles growth by catalysis of one enzyme only that produces cell boundary from within. This is the prototype of the simplest autopoietic minimal cell.     

GIS interpolations of witness tree records (1839–1866) for northern Wisconsin at multiple scales

To construct forest landscape of pre‐European settlement periods, we developed a GIS interpolation approach to convert witness tree records of the U.S. General Land Office (GLO) survey from point to polygon data, which better described continuously distributed vegetation. The witness tree records (1839–1866) were processed for a 3‐million ha landscape in northern Wisconsin, U.S.A. at different scales. We provided implications of processing results at each scale. Compared with traditional GLO mapping that has fixed mapping scales and generalized classifications, our approach allows presettlement forest landscapes to be analysed at the individual species level and reconstructed under various classifications. We calculated vegetation indices including relative density, dominance, and importance value for each species, and quantitatively described the possible outcomes when GLO records are analysed at three different scales (resolution). The 1 × 1‐section resolution preserved spatial information but derived the most conservative estimates of species distributions measured in percentage area, which increased at coarser resolutions. Such increases under the 2 × 2‐section resolution were in the order of three to four times for the least common species, two to three times for the medium to most common species, and one to two times for the most common or highly contagious species. We mapped the distributions of hemlock and sugar maple from the pre‐European settlement period based on their witness tree locations and reconstructed presettlement forest landscapes based on species importance values derived for all species. The results provide a unique basis to further study land cover changes occurring after European settlement.     

广东省种子植物分布新资料

报道广东省种子植物分布新记录2属——甜茅属(Glyceria R. Br.)及锦鸡儿属(Caragana Fabr.)，2个新记录种——甜茅[Glyceria acutiflora subsp. japonica (Steud.) T. Koyama et Kawano]及锦鸡儿[Caragana sinica (Buc’hoz) Rehder]，均发现于丹霞山国家级自然保护区。新记录的发现对于研究丹霞山的区系发生具有一定指示意义。     

The fossil record and estimating divergence times between lineages: Maximum divergene times and the importance of reliable phylogenies

Summary Bounded estimates on divergence times between lineaes are crucial to the calculation of absolute rates of molecular evolution. Upper (minimum) bounds on divergence times are easily estimated based on earliest fossil finds. Lower (maximum) bounds are more difficult to estimate; the age of putative ancestors may be used, though in practice it is virtually impossible to distinguish ancestors from primitive sister groups, which do not, of logical necessit, consitute lower bounds on divergence times. Two relatively new approaches to estimating lower bounds directly assess the incompleteness of the fossil record. The first uses taphonomic control groups to distinguish real absences from nonpreservation, while the second, and probably more powerful, uses the quality of the fossil recored to estimate confidence intervals on the bases of stratigraphic ranges. For some groups, especially vertebrates, the inclusion or exclusion of problematic fossils can dramaticaly affect estimated lower bounds on divergence times, often swamping the uncertainties due to the incompleteness of the fossil record and/or corelation and dating errors. When datable paleogeographic events reflect ancient divisions of faunas, a lower bound on the divergence time of speices within a fauna can be established based on the geologic, rather than fossil, record. The fossil records of hominids, eutherianmammals, echinoids, and geese are used as examples.This article was presented at the C.S.E.O.L. Conferrence on DNA-DNA Hybridization and Evolution, Lake Arrowhead, California, May 11–14, 1989