The Art Collector

Abstract

The initiating point of this paper was an article in AEPR by Peter J. Smith in March/April 2003. At the end of the article, Peter J. Smith provides a short answer.     

Long‐term survival and diversification of an endemic Melitaea species in mountains of Iran and adjacent areas

Disjunct distribution patterns regularly resulted in the separation of different genetic lineages in glacial refugia. Recent patterns of survival and expansion have been often revealed by climatic niche modelling. We used the combination of genetic markers, geometric morphometry and climatic niche modelling to clear up the taxonomy and reconstruct the potential range of an endemic Iranian, taxonomically disputed Melitaea species in climatically different epochs. Our results show that this species (Melitaea abbas Gross and Ebert 1975, comb. n. = M. zagrosi Tóth and Varga syn. nova) is clearly separated from all taxa of the Melitaea phoebe species group and only occurs in Iran and Azerbaijan but were also predicted for some adjacent regions. Molecular markers and distribution modelling show consistently that this species should have had a long‐term survival in this area, and its range could have been slightly larger during the last glacial maximum than currently. Based on the studied molecular markers, three main groups in M. abbas can be recognized: those of steppic area of Azerbaijan, western Iran and northeastern Iran. Each group is characterized by own mitochondrial haplotypes, but also a high level of genetic diversity appears in the central part of the distribution area (Zagros Mts.).     

Analysis of membrane fusion as a two-state sequential process: evaluation of the stalk model

We propose a model that accounts for the time courses of PEG-induced fusion of membrane vesicles of varying lipid compositions and sizes. The model assumes that fusion proceeds from an initial, aggregated vesicle state ((A) membrane contact) through two sequential intermediate states (I(1) and I(2)) and then on to a fusion pore state (FP). Using this model, we interpreted data on the fusion of seven different vesicle systems. We found that the initial aggregated state involved no lipid or content mixing but did produce leakage. The final state (FP) was not leaky. Lipid mixing normally dominated the first intermediate state (I(1)), but content mixing signal was also observed in this state for most systems. The second intermediate state (I(2)) exhibited both lipid and content mixing signals and leakage, and was sometimes the only leaky state. In some systems, the first and second intermediates were indistinguishable and converted directly to the FP state. Having also tested a parallel, two-intermediate model subject to different assumptions about the nature of the intermediates, we conclude that a sequential, two-intermediate model is the simplest model sufficient to describe PEG-mediated fusion in all vesicle systems studied. We conclude as well that a fusion intermediate "state" should not be thought of as a fixed structure (e.g., "stalk" or "transmembrane contact") of uniform properties. Rather, a fusion "state" describes an ensemble of similar structures that can have different mechanical properties. Thus, a "state" can have varying probabilities of having a given functional property such as content mixing, lipid mixing, or leakage. Our data show that the content mixing signal may occur through two processes, one correlated and one not correlated with leakage. Finally, we consider the implications of our results in terms of the "modified stalk" hypothesis for the mechanism of lipid pore formation. We conclude that our results not only support this hypothesis but also provide a means of analyzing fusion time courses so as to test it and gauge the mechanism of action of fusion proteins in the context of the lipidic hypothesis of fusion.     

Function of two β-carotenes near the D1 and D2 proteins in photosystem II dimers

The antenna proteins in photosystem II (PSII) not only promote energy transfer to the photosynthetic reaction center (RC) but provide also an efficient cation sink to re-reduce chlorophyll a if the electron transfer (ET) from the Mn-cluster is inhibited. Using the newest PSII dimer crystal structure (3.0 Å resolution), in which 11 β-carotene molecules (Car) and 14 lipids are visible in the PSII monomer, we calculated the redox potentials (E_m) of one-electron oxidation for all Car (E_m(Car)) by solving the Poisson-Boltzmann equation. In each PSII monomer, the D1 protein harbors a previously unlocated Car (Car_D1) in van der Waals contact with the chlorin ring of Chl_Z(D1). Each Car_D1 in the PSII dimer complex is located in the interface between the D1 and CP47 subunits, together with another four Car of the other PSII monomer and several lipid molecules. The proximity of Car bridging between Car_D1 and plastoquinone/Q_A may imply a direct charge recombination of Car⁺Q_A⁻. The calculated E_m(Car_D1) and E_m(Chl_Z(D1)) are, respectively, 83 and 126 mV higher than E_m(Car_D2) and E_m(Chl_Z(D2)), which could explain why Car_D2⁺ and Chl_Z(D2)⁺ are observed rather than the corresponding Car_D1⁺ and Chl_Z(D1)⁺.     

Drastic post‐LGM expansion and lack of historical genetic structure of a subtropical fig‐pollinating wasp (Ceratosolen sp. 1) of Ficus septica in Taiwan

The climatic oscillations of the last glacial period have had profound influences on the demography and levels of genetic diversity of extant species. Molecular evidence of glacial effects on temperate species has been well documented, whereas little is known regarding that on subtropical species. Here we present analyses based on partial sequences of the mitochondrial cytochrome c oxidase subunit I (COI) gene (1052 bp) and genotypes at 15 microsatellite loci to investigate the historical demography, population structure and ongoing gene flow of an undescribed fig‐pollinating wasp (Ceratosolen sp. 1) of Ficus septica in subtropical Taiwan. Reconstructed historical demography based on the coalescent tree of COI sequences suggests that C. sp. 1 has undergone a drastic population expansion which was tightly coupled with climatic changes since the last glacial maximum (LGM). The magnitude of the population size change was approximately 500‐fold, indicating that the population of this wasp and its host was likely highly compressed during the last glacial period. The lack of significant population differentiation (F_ST < 0.02, for all pairwise F_ST values) may be due to rapid postglacial expansion facilitated by long‐distance dispersal, although a low frequency of first‐generation migrants was detected. Our results clearly demonstrate how recent climatic changes since the LGM and dispersal ability have jointly shaped the genetic composition of a subtropical fig‐pollinating wasp.     

末次冰期以来中国海区浮游有孔虫Pulleniatina obliquiloculata含量变化的地层学意义

西北太平洋尤其是中国海区末次冰期旋回中浮游有孔虫Pulleniatina obliquiloculata含量变化研究是近年来最重要的古海洋学内容之一.作者综合分析了中国及邻近海区具有可靠测年地层的深海沉积物柱状样中P.obliquiloculata含量变化,探讨其含量低值事件(PME)的生物地层学意义.末次冰期以来P.obliquiloculata含量变化在中国海区呈现两种变化模式:一是以东海及南海北部为代表的冰期含量低、间冰期含量高的特点;另一种则是南海南部的冰期含量高、间冰期含量低的现象.高分辨率地层记录显示,在这种冰期/间冰期总体变化趋势基础上,我国东海、南海和黑潮源区等广泛存在晚全新世～4 300-2 800 cal yr BP P.obliquiloculata含量低值,但以南海北部与东海冲绳海槽最为明显;而南海南部P.obliquiloculata含量还在冰消期(～16.5-15 cal kyr BP)有另一特征的低含量阶段.因而,末次冰期旋回中国海区P.obliquiloculata含量变化可以作为区域性地层划分和对比的标志.尽管如此,由于黑潮分支水团的影响,冲绳海槽中部和北部部分海域,在末次冰期与PME期间,P.obliquiloculata虽然含量相对较低,但仍可保持3%-5%以上,而非多数站位PME事件中的特征性零含量.研究表明PME事件主要由次表层海水的温度降低、温跃层变浅、上部水体温度梯度增加等引起,与表层海水无关,但引起这些海洋环境变化的原因尚不清楚.     

芒和五节芒在中国的潜在分布

利用最大熵模型, 将我国现有芒(Miscanthus sinensis)和五节芒(M. floridulus)的地理分布信息与19个降水及温度等气候因子相拟合, 预测了芒和五节芒在我国的潜在分布区域, 并推测出芒和五节芒的基本生态位。结果显示: 芒的潜在适生区包括四川西部、陕西北部、宁夏、内蒙古中部、黑龙江、吉林西部、辽宁西部、青海东南部等地区, 其基本生态位参数为: 最暖季节降水量为400-1 000 mm, 平均8月降水量为100-350 mm, 7月平均最低气温为15 ℃, 平均7月降水量为100-350 mm, 11月平均最高气温为-10-22 ℃, 最干月平均气温为-15-20 ℃, 平均12月降水量为100 mm以下; 五节芒的潜在适生区为云南、陕西、山西、宁夏、河南、山东、吉林、辽宁以及四川西部、甘肃南部和内蒙古东部等地区, 其基本生态位参数为: 最暖季节降水量至少在400 mm以上, 平均6月降水量为150-550 mm, 7月平均最低气温在15-30 ℃之间, 6月平均最低气温为10 ℃, 平均4月降水量为50-100 mm。结果表明, 在进行遗传改良的前提下, 我国有丰富的适合栽植芒和五节芒的土地资源。     

三峡库区不同林龄人工橘林土壤异养呼吸及其温度敏感性

土壤异养呼吸是土壤碳库净输出的主要途径, 其对气候变暖的响应已引起国内外学者的广泛关注。对森林生态系统来说, 林龄是影响生态系统碳平衡的一个重要因素。柑橘作为三峡库区第一大支柱产业, 种植面积极广, 对维持该区域的生态平衡起着巨大的调节作用。该文以三峡库区宜昌市郊区种植年限不同的3个橘林土壤为研究对象, 采用室内培养法, 研究在不同温度条件下, 不同林龄土壤的异养呼吸及其温度敏感系数的差异, 探讨该区域生态系统对未来气候变化的潜在响应。结果显示, 随着种植年限的增加, 橘林土壤pH值减小, 有机质和全氮含量显著增加, 土壤微生物生物量碳呈下降趋势。无论在低温、常温还是高温条件下, 林龄较小的橘树土壤异养呼吸及其累积释放量较低。与其他研究相比, 该区域人工橘林土壤异养呼吸的温度敏感系数Q₁₀值相对较低(1.45-1.69), 且随着培养时间的变化而变化。随着种植年限的增加, 人工橘林土壤异养呼吸的温度敏感性逐渐降低, 表明在未来全球气候变暖条件下, 幼龄人工橘林要比成熟林对温度的反应敏感。