Autonomous cell death, temperature sensitivity and the genetic control associated with resistance to cucumber mosaic virus (CMV) in diploid potatoes (Solanum spp.)

Cucumber mosaic virus (CMV) is a commonly occurring plant virus that causes severe damage in many crops, including the diploid crop species tomato and pepper (Lycopersicon spp. and Capsicum spp., respectively) of the family Solanaceae, but it is neither common nor economically important in cultivated potatoes (Solanum tuberosum; Solanaceae). Resistance to CMV was examined in two diploid (2n=2x=24), highly heterozygous potato populations (Solanum spp.; Solanaceae) consisting of 76 and 126 progeny. Resistance to long-distance transport of CMV controlled by one locus with a major effect and functional at a low temperature (18°C) but overcome at a high temperature (28°C) was identified in one population. In the other population, resistance was controlled by two loci with major effects. In both populations, additional genes with minor effects were probably also involved. Induced resistance to CMV, associated with autonomously developing cell death lesions (Anl) previously not known in potato, was expressed in one parental line. The mechanisms of resistance to CMV may be associated with an inherent or developmental lack of host factors required for compatible CMV-host interactions in viral long distance transport and/or inability of CMV to efficiently suppress the host gene silencing mechanism in potatoes. Polyploidy (gene dose) and high heterozygosity (multiple homologous genes) of potato cultivars may be significant in conferring the durable resistance to CMV. These data provide explanations why CMV is not common and economically important in cultivated potatoes, even though CMV commonly occurs in other crops, weeds and wild plants in potato production areas. Received: 11 February 1999 / Accepted: 25 March 1999     

Divergent adaptation to Qinghai-Tibetan Plateau implicated from transciptome study of Gymnocypris dobula and Schizothorax nukiangensis

The Schizothoracine fishes are widely distributed in the Qinghai-Tibetan Plateau (QTP) area and its peripheral regions, which provide a prime example of adaptation in highland aquatic environments. Recent progresses have revealed various genetic adaptations of these fishes by comparing to distantly related lowerland species, however, comparative studies on closely-related species of different altitudes are still lacking. In this study, we sequenced and annotated a primitive Schizothoracine fish Schizothorax nukiangensis Tsao and a highly specialized one Gymnocypris dobula. We performed evolutionary analyses to investigate the candidate genes and signaling pathways involved QTP highland adaptation in both Schizothoracine fishes. Analysis of the 11,007 one-copy orthologs to the primitive cyprinid species, Danio rerio, revealed that both G. dobula and S. nukiangensis showed elevated evolutionary rates. A large number of genes related to hypoxia, including genes involved metabolic processes and cardiovascular system development, exhibited signatures of positive selection in both Schizothoracine fishes, but very few positively selected genes were found overlapping among these Schizothoracines. Our results indicated divergent genetic adaptation to highland environment for aquatic species living in QTP.     

西藏地区雪层杜鹃遗传多样性的AFLP分析

采用AFLP技术对西藏地区雪层杜鹃（Rhododendron nivale）5个天然种群135份材料进行遗传多样性和遗传分化研究。筛选得出的6对引物共扩增产物273条DNA片段,扩增多态位点百分率为85.71%。5个雪层杜鹃种群的遗传多样性指标表现了相似的变化趋势,Nei基因多样性指数（h）和Shannon信息指数（I）的变化趋势一致,均为工布江达县种群 < 米林种群 < 嘎隆拉种群 < 色季拉山种群 < 红拉山种群。POPGENE分析结果表明雪层杜鹃在物种水平（PPL=85.71%,I=0.415 1,h=0.273）具有较高的遗传多样性,种群水平（PPL=62.26%,I=0.280 3,h=0.184 1）的遗传多样性较低。AMOVA分析结果表明36%的遗传变异存在于种群间,64%的遗传变异存在于种群内,雪层杜鹃种群间的遗传分化系数（G_st=0.324）与AMOVA分析得到的遗传变异分布结果一致。UPGMA聚类结果说明雪层杜鹃的遗传距离与地理距离和海拔高度没有明显的相关性。综合分析,引起雪层杜鹃的遗传变异的原因可能是地理环境不同和种群的生境类型差异。最后就雪层杜鹃的合理开发和保护提出建议。     

Elevational diversity gradients of Tibetan loaches: The relative roles of ecological and evolutionary processes

It is widely believed that species richness patterns (SRPs) are shaped by both ecological and evolutionary processes. However, the relative roles of these processes remain unclear, especially for aquatic organisms. In this study, we integrated ecological and evolutionary measures to tease apart the relative influences of these factors on the SRP of Tibetan loaches along an extensive elevational gradient. We found that the Tibetan loaches displayed a richness pattern that peaked at midelevations. The mean annual temperature (MAT), mid‐domain effect (MDE), and summed age of colonization (SAC, complex of colonization age and colonization frequency) were the main drivers, accounting for 85%, 51%, and 88% of the variations in the SRP, respectively. The three predictors had very high combined effects (MAT‐MDE‐SAC, MAT‐SAC, and MDE‐SAC were 44%, 38%, and 6%, respectively). Our analyses suggested that energy input, time‐for‐speciation, and species dispersal may directly guide the SRP or mediate it by geometric constraints. Conclusively, the SRP of the Tibetan loaches with elevation is the outcome of interactions between biogeographical processes and regional ecological conditions.     

Breeding ecology of an Old World high-altitude warbler, Phylloscopus affinis

Reproduction of Tickell’s Leaf Warblers Phylloscopus affinis was studied in an alpine valley (29°27′N, 91°40′E, 3,980–5,600 m) in the Lhasa mountains, Tibet, at the upper elevational limit of the species’ breeding range. This species is a summer breeder, and is the only breeding Phylloscopus species in the valley. It nested in all types of shrubby vegetation across the altitudinal range of the valley. Most nests were placed close to the ground (<1 m) in low thorn bushes. Egg-laying dates fell between late May and early July, most within the first 3 weeks after the commencement of breeding. Mean clutch size was 4.0 (3–5) and mean brood size at fledging 3.4 (2–5). Incubation was by the females and lasted 13–14 days, and both parents cared for the young for 14–17 days. Nestlings ready to leave the nest were 13% heavier than the adults. Overall, 76% of nesting attempts produced at least one fledged young. Some aspects of the breeding biology of this high-altitude warbler were compared with those of lower-altitude Phylloscopus species.     

The youngest split in sympatric schizothoracine fish (Cyprinidae) is shaped by ecological adaptations in a Tibetan Plateau glacier lake

Although new empirical evidence shows that sympatric speciation has occurred in some species, there are few indisputable model organisms for this process of speciation. The two subspecies ( Gymnocypris eckloni eckloni and G . e . scoliostomus ) of the schizothoracine Gymnocypris fish species complex from a small glacier lake in the Tibetan Plateau, Lake Sunmcuo, fit several of the key characteristics of the sympatric speciation model. We used combined mitochondrial control region sequences and the cytochrome b gene (1894 bp) to address the phylogenetics and population genetics of 232 specimens of G . e . eckloni and G . e . scoliostomus , as well as all of its closely related sister species. We found that: (i) a total of four old lineages were uncovered in the widespread G . e . eckloni , of which only one was shown to be shared with all G . e . scoliostomus individuals and (ii) the new subspecies ( G . e . scoliostomus ) evolved in Lake Sunmcuo from the ancestral G . e . eckloni population within approximately 0.057 Ma. These two taxa of the species complex are morphologically distinct, and reproductive isolation is further suggested. Ecological disruptive selection based on morphological traits (e.g. mouth cleft characters) and food utilization may be a mechanism of incipient speciation of two sympatric populations within Lake Sunmcuo. This study provides the first genetic evidence for sympatric speciation in the schizothoracine fish.     

Impacts of human activity on environment in the high-cold pasturing area: A case of Gannan pasturing area

Identifying the specific forces driving environmental impact is a hot topic in the field of sustainable development in the pasturing area. In the paper, the ecological footprint was taken as the index of environmental impact, and a series of index like population quality, prosperous, using intensity, livelihood tactics are considered as the main human factors. Using the STIRPAT model and temporal series data from 1980 to 2007, the author analyzes the effects of the human driving forces of environmental impact.
The ecological footprint method presents a simple framework for national natural capital accounting, and it has been used as a comprehensive index of human activity impact, which indirectly reflect human activity’s pressure on the environment. Our analyses showed that the ecological footprint increased from 238736.9 to 877716.1 ha and per capital ecological footprint also increased from 0.854 to 1.961 ha/per during 1980–2007 in Gannan pasturing area. However, in the meantime, the ecological footprint intensity was inclined from 25.396 to 3.025 ha/ten thousand yuan.
With a view of dismantling the human driving forces of ecological footprint, the modified IPAT-called STIRPAT has been employed as a common analytic framework. Our analyses showed that population quantity and using intensity was a major driver of ecological footprint, their coefficients were greater than 1.0 in model (1); In addition, promoting the prosperous lever and the primary industry proportion, the impact of environment will be increased, but their coefficients are less than 1.0 in model (1). At the same time, the technological eco-efficiency of sample regions was discussed in details, the range ability of the technological eco-efficiency was wider, and 15 years went beyond the average level, but the other was less than the average level. Another important finding in the empirical study is that there are some evidences of an environmental Kuznets curve for ecological footprint within the range of calculated data. Some potential improvements in some further researches and suggestions to alleviate the environment pressure, and it is put forward in the last section.     

Phylogeographical Study on Eriophyton wallichii (Labiatae) from Alpine Scree of Qinghai Tibetan Plateau

In this study, we examined the nuclear ribosomal DNA internal transcribed spacer (ITS) sequence variation of Eriophyton wallichii, a perennial endemic to alpine scree of the Qinghai Tibetan Plateau. Nineteen haplotypes were detected by analyzing 187 individuals from 20 populations of E.wallichii. Most populations hold the unique haplotype, which showed different population with different haplotype. An analysis of molecular variance (AMOVA) for populations showed that the genetic variation mainly resided among populations (89.54%), the level of differentiation among populations was very high (GST=0.863; NST=0.957) but didn’t show a significant phylogeographical structure. It is different from foregoing other species reported in Qinghai Tibetan Plateau that the haplotypes of E.wallichii showed a distribution pattern that almost one population hold one unique haplotype, hardly share same halotype among populations.We hypothesized the unique genetic structure of E.wallichii might result from allopatric fragmentation in the “islands of alpine” due to the extremely isolated alpine scree and rough topography of the region, through the Quaternary climate oscillation dramatically caused population expanding or shrinking.     

Comparative Physiological and Molecular Analyses of Intraspecific Differences of Stipa purpurea (Poaceae) Response to Drought

Stipa purpurea Griseb, the dominant species of alpine steppe, is widely distributed across the large precipitation gradient on the Tibetan Plateau. It is possible that because of local adaptation, Spurpurea populations from different habitats along this precipitation gradient respond differently to drought, which may affect their responses to climate change. To explore the problem, in the present study, we investigated the physiological and molecular response of Spurpurea seedlings from two different populations (Pulan & Cuoqin) to 14 d drought stress and subsequent recovery. The results showed that the relative water content, chlorophyll fluorescence, content of osmoticant proline and malondialdehyde (indicator of oxidative stress), accumulation of reactive oxygen species, antioxidant enzyme activities and the expression of drought related genes all changed under drought treatment and went back to the control levels in the subsequent recovery in plants from Pulan. However, these patterns were quite different in plants from Cuoqin, in which these traits changed by inconsistent degrees and did not return to pretreatment levels after rewatering. The results demonstrated that the plants from Pulan had greater resistance to drought stress compared with those from Cuoqin, which had a larger mortality rate ultimately. Combating the differences of offspring in response to drought and the habitat distribution of parents, we considered that genetic basis has been obtained in response to precipitation difference among Spurpurea populations. The results help to understand the adaptation and evolution of Spurpurea to the special environment and the effect of climate change to this botanical system.     

Linking species performance to community structure as affected by UV-B radiation: an attenuation experiment

Aims UV-B radiation is known to affect plant physiology and growth rate in ways that can influence community species composition and structure. Nevertheless, comparatively little is known about how UV-B radiation induced changes in the performance of individual species cascades to affect overall community properties. Because foliage leaves are primarily responsible for photosynthesis and carbon gain and are the major organ that senses and responds to UV-B radiation, we hypothesized that, under reduced UV-B radiation, species with larger leaf areas per plant would manifest higher growth rates and hence tend to improve their community status compared to species with smaller leaf areas per plant in herbaceous plant communities.Methods We tested this hypothesis by examining plant traits (leaf area per plant and plant height), plant growth rate (aboveground biomass per plant and plant biomass per area) and community status (species within-community relative biomass) for 19 common species in a two-year field experiment in an alpine meadow on Tibetan Plateau.Important findings Aboveground biomass per plant, as well as per area, progressively increased in a 39% reduced (relative to ambient) UV-B treatment during the experimental period. At the second year, 11 out of 19 species significantly or marginally significantly increased their plant height, leaf area per plant and aboveground biomass per plant. No species was negatively affected by reducing UV-B. As hypothesized, the increase in aboveground biomass per plant increased with increasing leaf area per plant, as indicated by cross-species regression analysis. Moreover, the change in species within-community status increased with increasing leaf area per plant. Our study demonstrates that UV-B radiation has differential effects on plant growth rate across species and hence significantly affects species composition and plant community structure. We suggest that UV-B radiation is an ecological factor structuring plant communities particularly in alpine and polar areas.