Phylogeography and Genetic Ancestry of Tigers (Panthera tigris)

Eight traditional subspecies of tiger (Panthera tigris), of which three recently became extinct, are commonly recognized on the basis of geographic isolation and morphological characteristics. To investigate the species' evolutionary history and to establish objective methods for subspecies recognition, voucher specimens of blood, skin, hair, and/or skin biopsies from 134 tigers with verified geographic origins or heritage across the whole distribution range were examined for three molecular markers: (1) 4.0 kb of mitochondrial DNA (mtDNA) sequence; (2) allele variation in the nuclear major histocompatibility complex class II DRB gene; and (3) composite nuclear microsatellite genotypes based on 30 loci. Relatively low genetic variation with mtDNA, DRB, and microsatellite loci was found, but significant population subdivision was nonetheless apparent among five living subspecies. In addition, a distinct partition of the Indochinese subspecies P. t. corbetti into northern Indochinese and Malayan Peninsula populations was discovered. Population genetic structure would suggest recognition of six taxonomic units or subspecies: (1) Amur tiger P. t. altaica; (2) northern Indochinese tiger P. t. corbetti; (3) South China tiger P. t. amoyensis; (4) Malayan tiger P. t. jacksoni, named for the tiger conservationist Peter Jackson; (5) Sumatran tiger P. t. sumatrae; and (6) Bengal tiger P. t. tigris. The proposed South China tiger lineage is tentative due to limited sampling. The age of the most recent common ancestor for tiger mtDNA was estimated to be 72,000–108,000 y, relatively younger than some other Panthera species. A combination of population expansions, reduced gene flow, and genetic drift following the last genetic diminution, and the recent anthropogenic range contraction, have led to the distinct genetic partitions. These results provide an explicit basis for subspecies recognition and will lead to the improved management and conservation of these recently isolated but distinct geographic populations of tigers

Proceedings in Phylogeography and Genetic Ancestry of Tigers ( Panthera tigris ) in China and Across Their Range

Of eight traditionally classified subspecies of the tiger Panthera tigris three have recently gone extinct and poaching, habitat loss and fragmentation continue to threaten its survival. China historically harbors four of the existing subspecies and thus has high conservation priority, yet their status, both in the wild and captivity, remains highly uncertain. A recent molecular survey (Luo et al, 2004) of 134 "voucher specimens" (taken from tigers of verified wild ancestry and geographic origin), from across the full range including China, examined three different types of molecular markers; four kilobase-pairs of mitochondrial DNA, 30 nuclear microsatellite loci and the nuclear major histocompatibility complex class II DRB gene; to elucidate the genetic structure of tiger populations. The data revealed relatively low genetic variation but nonetheless significant population subdivisions, suggesting six rather than five living subspecies: (1) Amur tiger P. t. altaica, (2) South China tiger P. t. amoyensis, (3) a refined Indochinese tiger P. t. corbetti, (4) a new subspecies Malayan tiger P. t. jacksoni, named after the tiger conservationist Peter Jackson, (5) Sumatran tiger P. t. sumatrae, and (6) Bengal tiger P. t. tigris. Reduced gene flow and genetic drift in isolated populations since the last genetic diminution about 72 000-108 000 years ago, as well as the recent anthropogenic range contraction, is likely to have caused these partitions. In particular, the proposed South China tiger lineage is tentative due to limited sampling. It is apparent that current captive South China tigers inherit at least two genetic lineages: one that is unique and distinct from the other subspecies and a second indistinguishable from the northern Indochinese tigers. An explicit genetic assessment of the captive tigers in China is urgently needed to validate the uniqueness or non-uniqueness of the South China tiger, or indeed the survival of P. t. amoyensis

Structure and Patterns of Sequence Variation in the Mitochondrial DNA Control Region of the Great Cats

Mitochondrial DNA control region structure and variation were determined in the five species of the genus Panthera. Comparative analyses revealed two hypervariable segments, a central conserved region, and the occurrence of size and sequence heteroplasmy. As observed in the domestic cat, but not commonly seen in other animals, two repetitive sequence arrays (RS-2 with an 80-bp motif and RS-3 with a 6–10-bp motif) were identified. The 3′ ends of RS-2 and RS-3 were highly conserved among species, suggesting that these motifs have different functional constraints. Control region sequences provided improved phylogenetic resolution grouping the sister taxa lion (Panthera leo) and leopard (Panthera pardus), with the jaguar (Panthera onca)

Performance of CoMoS catalysts supported on nanoporous carbon in the hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene

A new type of nanoporous carbon with a large surface area and mesoporosity was prepared and used as a support for a hydrodesulfurization (HDS) catalyst. The overall activity of CoMoS catalysts for the HDS of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) is affected by the type of support used for preparing the catalyst and decreases in the order of CoMo/(nanoporous carbon) > CoMo/(activated carbon) > CoMo/Al2O3. The surface area of activated carbon is the largest among these three types of supports but is significantly lowered after metal loading during the preparation of the catalyst. On the other hand, the surface areas of the other two supports are largely preserved after metal loading. The intrinsic activity of the catalysts, estimated by dividing the overall HDS rate by the amount of NO adsorbed on the catalyst, shows a trend that is different from that for the overall activity, and follows the order of CoMo/(nanoporous carbon) approximate to CoMo/Al2O3 > CoMo/(activated carbon). The low intrinsic activity of CoMo/(activated carbon) compared to that of the other two catalysts, particularly in the case of 4,6-DMDBT HDS, is obtained because the diffusion of reactants into the catalyst pores is significantly limited. This is not observed with other catalysts supported on nanoporous carbon and alumina. From the results of this study, we conclude that nanoporous carbon is a promising support for HDS catalysts, compared to conventional supports such as alumina and activated carbon, because it has a large surface area and a high mesoporosity, both of which are beneficial to the preparation of highly dispersed metal catalysts without significant pore blocking due to the dispersed metal particles. (C) 2003 Elsevier B.V. All rights reserved.

STRUCTURE OF MN-ZR MIXED-OXIDE CATALYSTS AND THEIR CATALYTIC PROPERTIES IN THE CO HYDROGENATION REACTION

MnZr oxide catalysts with varying MnZr ratio were prepared by a coprecipitation method. Their structure and catalytic properties were studied by means of N2 adsorption, XRD, TPR, and CO hydrogenation as a probe reaction. The precipitated MnZr mixed oxide was composed of a mixture of large particles of manganese oxide and small particles of zirconium oxide. Addition of Mn retarded the growth of fine particles of zirconium oxide. By calcination at high temperature, part of the manganese oxide forms a solid solution with zirconium oxide and deposits on the surface of zirconium oxide as a thin layer. The type of Mn present in the mixed oxide affected the selectivity pattern in the CO hydrogenation. The bulk Mn exhibited a high selectivity to isobutene, but products contained hydrocarbons higher than C5. Mn dispersed on the surface of zirconium oxide showed a similar selectivity pattern to bulk Mn, but hydrocarbon chain growth was limited to C4 or lower. The formation of a solid solution enhanced production of lower hydrocarbons, especially methane. © 1992.close243

K2CO3??? ????????? MoS2 ????????? ?????? ?????????????????? ?????????????????? ???????????? ??????

?????????????????? ???????????????, ???????????? ??????????????? K2CO3??? ???????????? ?????? MoS2 ??? ??????????????? ????????????, ???????????? ??? ???????????? ?????? ????????? ??????, ??????, ?????? ?????? ????????? ???????????? ?????? ?????? ??????????????? ???????????????. ????????? MoS2 ????????? ????????? ????????? ????????? ???????????? ???????????? C1-C6 ????????? ????????? ????????? ?????? ?????? ???????????? ???????????????. ?????? ?????? ???????????? ?????? ?????? ?????? ????????? ????????? ?????? 17wt%, ?????? 300???????????????, ????????? ????????? ?????? ????????? ???????????????. ??? ??? ?????? ???????????? ???????????? ?????? ????????? ???????????? Schulz-Flory ????????? ???????????????.clos

Mn/Zr ??????????????? ????????? ?????? ??? CO??????????????? ??????

??????????????? Mn/Zr ??????????????? ????????? ???????????? ?????? ????????? CO ?????????????????? ????????? ????????????. ????????? ????????? ??????????????? XRD, ESCA??? ???????????????. ??????????????? ????????? ?????? ???????????? ???????????????????????? monoclinic????????? ??????????????????, ??????????????? ??????????????? ?????????. ????????? ????????? ???????????????????????? ???????????? ????????? ????????????, ????????? ???????????? ???????????????. ?????? Mn/Zr ??????????????? ???????????? ????????? ????????? ?????? ????????? ???????????? ????????? ????????????. ?????????????????? ???????????????????????? ??? ??? ?????? ????????? ???????????? ????????? ????????????, Mn/Zr ??????????????? ????????? ????????? ????????????????????? ?????????. Mn/Zr ??????????????? ???????????? solid solution??? ????????? C2-C4 ????????? ??????????????? ????????? ????????????.clos

Phylogeography, Population History and Conservation Genetics of Jaguars (Panthera onca, Mammalia, Felidae)

The jaguar (Panthera onca), the largest felid in the American Continent, is currently threatened by habitat loss, fragmentation and human persecution. We have investigated the genetic diversity, population structure and demographic history of jaguars across their geographical range by analysing 715 base pairs of the mitochondrial DNA (mtDNA) control region and 29 microsatellite loci in ≈40 individuals sampled from Mexico to southern Brazil. Jaguars display low to moderate levels of mtDNA diversity and medium to high levels of microsatellite size variation, and show evidence of a recent demographic expansion. We estimate that extant jaguar mtDNA lineages arose 280 000–510 000 years ago (95% CI 137 000–830 000 years ago), a younger date than suggested by available fossil data. No strong geographical structure was observed, in contrast to previously proposed subspecific partitions. However, major geographical barriers such as the Amazon river and the Darien straits between northern South America and Central America appear to have restricted historical gene flow in this species, producing measurable genetic differentiation. Jaguars could be divided into four incompletely isolated phylogeographic groups, and further sampling may reveal a finer pattern of subdivision or isolation by distance on a regional level. Operational conservation units for this species can be defined on a biome or ecosystem scale, but should take into account the historical barriers to dispersal identified here. Conservation strategies for jaguars should aim to maintain high levels of gene flow over broad geographical areas, possibly through active management of disconnected populations on a regional scale