The activity of the plant mitochondrial inner membrane anion channel (PIMAC) of maize populations divergently selected for cold tolerance level is differentially dependent on the growth temperature of seedlings

The activity of the plant inner membrane mitochondrial anion channel (PIMAC) is involved in metabolite shuttles and mitochondrial volume changes and could have a role in plant temperature tolerance. Our objectives were to investigate (i) the occurrence and (ii) the temperature dependence of anion fluxes through PIMAC in mitochondria isolated from seedlings of three maize populations differing in terms of cold tolerance; and (iii) the relationships between the PIMAC activity kinetics and the level of cold tolerance. Populations were the source population (C0) and two populations divergently selected for high (C4H) and low (C4L) cold tolerance. Such divergently selected populations are expected to share most of their genes, with the main exception of those genes controlling cold tolerance. Arrhenius plots of PIMAC chloride fluxes showed a linear temperature dependence when seedlings were grown at 25 or 14°C, whereas a non-linear temperature dependence was found when seedlings were grown at 5°C, with or without acclimation at 14°C. The activation energy and other thermodynamic parameters of PIMAC activity varied depending on temperature treatments during seedling growth. When seedlings were grown at 14 and 5°C with acclimation, PIMAC activity of the C4H population increased, while that of C4L declined, as compared with the activities of seedlings grown at 25°C. These symmetric responses indicate that PIMAC activity changes are associated with genetically determined differences in the cold tolerance level of the investigated populations. We conclude that anion fluxes by PIMAC depend upon changes on growth temperature and are differentially related to the tolerance level of the tested populations.     

内蒙古高原甘蒙锦鸡儿的遗传分化研究

对分布于内蒙古和林格尔和阿拉善的甘蒙锦鸡儿(Caragana opulens Kom)种群的叶片形态特性和遗传结构进行了比较研究。结果发现:从叶厚度、面积、长/宽、生物量及SLA来看,阿拉善种群与和林格尔种群之间存在明显变异,阿拉善种群比和林格尔种群保水能力强,对干旱的适应能力好。遗传结构比较研究发现,甘蒙锦鸡儿种群间发生明显的遗传分化(遗传相似度为0.711),表明生物对环境的适应是有分子基础的、是以遗传变异为基础的种群分化适应。     

光温条件明显影响棉铃虫的滞育强度

为了探明不同地理种群棉铃虫Helicoverpa armigera滞育强度的地理变异, 本研究系统地比较了光温条件（光照时数 11～16 h, 恒温20, 22, 25, 28和31℃及变温）对来自中国的4个地理种群（广东广州、 江西永修、 山东泰安和辽宁喀佐）棉铃虫滞育强度的影响。结果表明： 滞育诱导的光周期对继后棉铃虫的滞育强度有明显影响。在光照时数11～14 h范围内, 各地理种群的滞育持续期均随着光照时数的增加而延长。滞育强度也受到滞育诱导的温周期影响, 当光期温度相同时, 低纬度的GZ种群温周期比恒温有更强的诱导效应; 中纬度的YX种群温周期与恒温具有相同的滞育诱导强度; 高纬度的KZ和TA种群温周期所诱导的滞育强度一般低于恒温。滞育解除过程中的温度也显著影响到滞育的解除, 在20~31℃下, 温度愈高滞育解除愈快; 滞育持续期同时受到滞育诱导温度的影响, 对于北方的泰安种群和喀佐种群, 较高的滞育诱导温度能诱导更强的滞育。     

Olive Fruit Fly (Bactrocera oleae) Population Dynamics in the Eastern Mediterranean: Influence of Exogenous Uncertainty on a Monophagous Frugivorous Insect

Despite of the economic importance of the olive fly (Bactrocera oleae) and the large amount of biological and ecological studies on the insect, the factors driving its population dynamics (i.e., population persistence and regulation) had not been analytically investigated until the present study. Specifically, our study investigated the autoregressive process of the olive fly populations, and the joint role of intrinsic and extrinsic factors molding the population dynamics of the insect. Accounting for endogenous dynamics and the influences of exogenous factors such as olive grove temperature, the North Atlantic Oscillation and the presence of potential host fruit, we modeled olive fly populations in five locations in the Eastern Mediterranean region. Our models indicate that the rate of population change is mainly shaped by first and higher order non-monotonic, endogenous dynamics (i.e., density-dependent population feedback). The olive grove temperature was the main exogenous driver, while the North Atlantic Oscillation and fruit availability acted as significant exogenous factors in one of the five populations. Seasonal influences were also relevant for three of the populations. In spite of exogenous effects, the rate of population change was fairly stable along time. We propose that a special reproductive mechanism, such as reproductive quiescence, allows populations of monophagous fruit flies such as the olive fly to remain stable. Further, we discuss how weather factors could impinge constraints on the population dynamics at the local level. Particularly, local temperature dynamics could provide forecasting cues for management guidelines. Jointly, our results advocate for establishing monitoring programs and for a major focus of research on the relationship between life history traits and populations dynamics.     

The benefits of interpopulation hybridization diminish with increasing divergence of small populations

Interpopulation hybridization can increase the viability of small populations suffering from inbreeding and genetic drift, but it can also result in outbreeding depression. The outcome of hybridization can depend on various factors, including the level of genetic divergence between the populations, and the number of source populations. Furthermore, the effects of hybridization can change between generations following the hybridization. We studied the effects of population divergence (low vs. high level of divergence) and the number of source populations (two vs. four source populations) on the viability of hybrid populations using experimental Drosophila littoralis populations. Population viability was measured for seven generations after hybridization as proportion of populations facing extinction and as per capita offspring production. Hybrid populations established at the low level of population divergence were more viable than the inbred source populations and had higher offspring production than the large control population. The positive effects of hybridization lasted for the seven generations. In contrast, at the high level of divergence, the viability of the hybrid populations was not significantly different from the inbred source populations, and offspring production in the hybrid populations was lower than in the large control population. The number of source populations did not have a significant effect at either low or high level of population divergence. The study shows that the benefits of interpopulation hybridization may decrease with increasing divergence of the populations, even when the populations share identical environmental conditions. We discuss the possible genetic mechanisms explaining the results and address the implications for conservation of populations.     

Variability in life history traits of the aphid,Acyrthosiphon pisum (Harris), from sexual and asexual populations

Many aphid species have shown remarkable adaptability by invading new habitats and agricultural crops, although they are parthenogenetic and might be expected to show limited genetic variation. To determine if the mode of reproduction limits the level of genetic variation in adaptively important traits, we assess variation in 15 life history traits of the pea aphid, Acyrhosiphon pisum (Harris), for five populations sampled along a north-south transect in central North America, and for three traits for three populations from eastern Australia. The traits are developmental times and rates as affected by temperature, body weights as affected by temperature, fecundity, measures of migratory tendency, and photoperiodic responses. The most southerly population from North America is shown to be obligately parthenogenetic, as are the Australian populations, and the four more northerly North American populations are facultatively parthenogenetic with the number of parthenogenetic generations per year increasing from north to south. The broad-sense heritabilities of life history traits varied from 0.36 to 0.71 for nine quantitive traits based on a comparison of within-and between-lineage variances. Using these traits, 7–13 distinct genotypes (i.e. clones) were identified among each of the 18 lines sampled from the North American populations, but the number did not differ significantly among populations. The level of genetic variation differed from trait to trait. For 4 of 12 quantitative traits, the level of variation in the obligately parthenogenetic population from North America was lowest, but significantly lower than all the sexual populations for only 1 trait. The obligately parthenogenetic population had the highest level of genetic variation for two traits, and had intermediate levels for the others. The most northerly population, which was sexual and had relatively few parthenogenetic generations each year, had the lowest level of variation for 5 of 12 traits and the highest level of variation for 2 traits. There was no decline in variability from north to south correlated with the increase in the annual number of parthenogenetic generations. The Australian populations showed no less variation than the North American populations for two of three traits, although the pea aphid was introduced to Australia only 5 years prior to the study, whereas the aphid has been in North America for at least 100 years. The mode of reproduction has not had a substantial impact on the level of genetic variation in life history traits of the pea aphid, but there are population-specific factors that effect the level of variation in certain traits.     

GENETIC AND ENVIRONMENTAL CONTROL OF GLYCOLIC ACID OXIDASE ACTIVITY IN ECOTYPIC POPULATIONS OF TYPHA LATIFOLIA

Glycolic acid oxidase activity at 25 C in leaf homogenates of ecotypic populations of Typha latifolia varied according to native climate of the population and current growing conditions. Activity of plants grown under warm/short day conditions was positively correlated with maximum summer temperature at the site of population origin. Activity of plants grown under cool/ long day conditions was negatively correlated with length of growing season at the site of origin. Populations from sites characterized by a long growing season are much less susceptible to environmental regulation of enzymic level than populations originating in short growing season sites. Enzyme activity is not a secondary reflection of differentiation at the level of chlorophyll or cofactor concentration. Enzymic differences between ecotypic populations reflect differences in control systems at the level of protein synthesis and genetic structure.     

中国杯萼海桑遗传多样性的ISSR研究

杯萼海桑(Sonneratia alba J.Smith.)是海桑科红树植物,在我国分布于海南岛的东海岸.本文采用简单序列霞复区间扩增(ISSR)分子标记技术对分布于海南岛的杯萼海桑的4个天然居群和东寨港红树林自然保护区引种的一人工居群共100个个体进行了遗传变异分析.11个引物共扩增出133条带,其中103条具多态性,多态位点百分率为77.44%.在居群水平上相对较低,多态位点百分率为51.88%～65.41%,平均为57.74%.期望杂合度、香农信息指数在物种水平上分别为0.227 1和0.348 9;在居群水平上分别为0.1 83 7和0.227 5.依据Gst值,杯萼海桑绝大多数遗传变异发生在居群内的个体间(81.02%),18.98%的遗传变异发生在居群间.AMOVA分析也表明了类似的遗传结构.居群间平均遗传一致度为0.934 2.依据Nei(1972)的遗传距离对不同居群进行UPGMA聚类,将居群分为两组,来自三亚(SY)和陵水(LS)的居群聚为一类;东寨港引种栽培的人工居群(DZ)和琼海(QH)、文昌(WC)的居群聚为另一类.Mantel检验表明,遗传距离与地理距离呈极显著相关.     

The Effects of Soil Type,Particle Size, Temperature,and Moisture on Reproduction of Belonolaimus longicaudatus

Effects of soil type, particle size, temperature, and moisture on the reproduction of Belonolaimus longicaudatus were investigated under greenhouse conditions. Nematode increases occurred only in soils with a minimum of 80% sand and a maximum of 10% clay. Optimum soil particle size for reproduction of the Tarboro, N.C. and Tifton, Ga. populations of the nematode was near that of 120-370 μm (65-mesh) silica sand. Reproduction was greatest at 25-30 C. Some reproduction by the Tifton, Ga. population occurred at 35 C, whereas the Tarboro, N.C. population declined, as compared to the initial inoculum. Both populations reproduced slightly at 20 C. Nematode reproduction was greater at a moisture level of 7% than at a high of 30% or a low of 2%. Reproduction occurred at the high moisture level only when the nutrient solution was aerated.     

Intraspecific variation in resistance of frog eggs to fungal infection

Documenting sources of variation in host viability at pathogen exposure within and among populations is an important task in order to predict host-pathogen evolutionary dynamics. In the present study, we investigated family and population variation in the degree of embryonic infection of the pathogenic fungus Saprolegnia spp., by infecting moor frog (Rana arvalis) eggs from six populations and exposing them to two different temperatures. We found a significant family effect on the degree of Saprolegnia-infection of eggs and embryos, suggesting that there is genetic variation in resistance among embryos, or variation among females in some aspect of maternally induced resistance. Furthermore, infection level differed significantly between temperatures, with most families having more infected eggs in the relatively colder temperature. However, eggs and embryos from the different populations showed different degrees of Saprolegnia-infection in the two temperatures, i.e., there was a significant population × temperature interaction on the proportion of infected eggs. Thus, the degree of Saprolegnia-infection is sensitive to variation at the level of the family, population and environmental conditions, suggesting that responses to fungal outbreaks will vary geographically and will be difficult to predict.     

温度对2个地理种群莲草直胸跳甲成虫产卵量及存活率的影响

【背景】温度对莲草直胸跳甲种群增长具有重要作用,了解引进的莲草直胸跳甲泰国种群的温度适应性,同时与福州本地种群相比较,可以有效地利用其防治空心莲子草。【方法】采用室内继代饲养的方法,设置3个温度,对莲草直胸跳甲福州本地种群和泰国热带种群的成虫产卵量及存活率进行了研究。【结果】在相同温度条件下,泰国热带种群的繁殖力显著高于福州本地种群。随着温度的升高,泰国热带种群和福州本地种群的产卵量均有显著下降,但泰国热带种群的产卵量均稍高于福州本地种群。在3个试验温度下,莲草直胸跳甲泰国热带种群的成虫寿命较福州本地种群的寿命长。【结论与意义】莲草直胸跳甲泰国热带种群对温度的适应性和繁殖力强,更容易构建种群,有利于对空心莲子草的生物防治。     

SEX RATIO SELECTION AND THE EVOLUTION OF ENVIRONMENTAL SEX DETERMINATION IN LABORATORY POPULATIONS OF MENIDIA MENIDIA

What happens when a population with environmental sex determination (ESD) experiences a change to an extreme environment that causes a highly unbalanced sex ratio? Theory predicts that frequency-dependent selection would increase the proportion of the minority sex and decrease the level of ESD in subsequent generations. We empirically modeled this process by maintaining five laboratory populations of a fish with temperature-dependent sex determination (the Atlantic silverside, Menidia menidia) in extreme constant temperature environments that caused highly skewed sex ratios to occur initially. Increases in the minority sex consistently occurred from one generation to the next across all five populations, first establishing and then maintaining a balanced sex ratio until termination of the experiment at 8 to 10 generations. The extent to which the level of ESD changed as balanced sex ratios evolved, however, was not consistent. Two populations that experienced high temperatures each generation displayed a loss of ESD, and in one of these ESD was virtually eliminated. This suggests that temperature-insensitive, sex-determining genes were being selected. In populations maintained in low temperature environments, however, the level of ESD did not decline. Instead, the response of sex ratio to temperature was adjusted upward or downward, perhaps by selection of sex-determining genes sensitive to higher (or lower) temperatures. The two different outcomes at low versus high temperatures occurred independent of the geographic origin of the founding population. Our results demonstrate that ESD is capable of evolving in response to selection.     

Genetic variation and structure of house sparrow populations: is there an island effect?

Population genetic structure and intrapopulation levels of genetic variation have important implications for population dynamics and evolutionary processes. Habitat fragmentation is one of the major threats to biodiversity. It leads to smaller population sizes and reduced gene flow between populations and will thus also affect genetic structure. We use a natural system of island and mainland populations of house sparrows along the coast of Norway to characterize the different population genetic properties of fragmented populations. We genotyped 636 individuals distributed across 14 populations at 15 microsatellite loci. The level of genetic differentiation was estimated using F‐statistics and specially designed Mantel tests were conducted to study the influence of population type (i.e. mainland or island) and geographic distance on the genetic population structure. Furthermore, the effects of population type, population size and latitude on the level of genetic variation within populations were examined. Our results suggest that genetic processes on islands and mainland differed in two important ways. First, the intrapopulation level of genetic variation tended to be lower and the occurrence of population bottlenecks more frequent on islands than the mainland. Second, although the general level of genetic differentiation was low to moderate, it was higher between island populations than between mainland populations. However, differentiation increased in mainland populations somewhat faster with geographical distance. These results suggest that population bottleneck events and genetic drift have been more important in shaping the genetic composition of island populations compared with populations on the mainland. Such knowledge is relevant for a better understanding of evolutionary processes and conservation of threatened populations.     

POPULATION VARIABILITY IN DANTHONIA CAESPITOSA (GRAMINEAE) IN RESPONSES TO INCREASING DENSITY UNDER THREE TEMPERATURE REGIMES

The objective of this research was to compare the responses to increasing density of different natural populations of Danthonia caespitosa, a perennial grass of southern Australia, under different temperature regimes. Seeds were collected from four populations along a 167-km N–S transect beginning north of Deniliquin, N.S.W., and ending near Heathcote, Victoria. Seedlings from each population were planted in loamy sand at three densities and grown under day/night temperature regimes of 15/10, 24/19, and 33/28 C in the Canberra Ceres Phytotron. Results indicate that one natural population (or one temperature regime) can not be used to characterize this species' responses to increasing density. The effects of density and temperature on tillering, plant height, leaf length, and leaf width varied significantly among populations, so that populations achieved comparable shoot weights by different relative responses to density. Variability in biomass among individuals (as indicated by coefficients of variation) increased from low to intermediate density; however, size variability at the highest density was either greater, lesser, or approximately the same as that of plants at the intermediate density, depending upon the population and the temperature regime. The combinations of density and temperature which produced the maximum shoot growth per pot varied markedly among populations; at 24/19 C, populations from frequently disturbed areas of low perennial plant cover had greater shoot weights per pot at the intermediate density, while those populations from more stable grassland sites had their greatest shoot weights at the highest density. Flowering occurred in all populations at the low density in 15/10 C; however, only for the population from the ungrazed grassland was there any flowering in the other temperature regimes or at higher densities. It is concluded that a “response to density stress” could be differentially described for each population at each temperature regime, even though the four study populations represented only 1/10 of the latitudinal range of D. caespitosa.     

川西泡沙参种群地上生物量生长发育的研究

对川西泡沙参种群地上各器官,茎、叶、花-果的生物量生长发育过程进行了系统的研究,结果表明：（1）泡沙参种群（总和）个体地上总生物量和各器官的生长发育在1-5年生生长缓慢,5-15年生随年龄增长,年生物量增幅较大,此后,生长速度开始下降,直到死亡年龄,泡沙参种群（总和）地上生物量生长发育过程可程可用方程y=a0 a1x a2x^2表示。（2）不同海拔区间的泡沙参种群个体地上总生物量和各器官生物量生长发育与种群（总和）地上总生物量生长发育的趋势基本一致。生物量生长在幼年和老年时较低,大约在15年生时达到高峰。（3）不同海拔区域综合生境条件与种群的地上生物量生长,生长模式,生物量最高峰出现的年龄区段等有着密切联系。在较为适生的环境条件下,外界干扰少,水热条件适宜,种群各器官的生物量和个体总生物量可达到较高水平,在低海拔地区,外界干扰严重,或高海拔地区,低温条件来酷,个体总生物量和各器官生物量均较低。     

Provenance matters: thermal reaction norms for embryo survival among sockeye salmon Oncorhynchus nerka populations

Differences in thermal tolerance during embryonic development in Fraser River sockeye salmon Oncorhynchus nerka were examined among nine populations in a controlled common‐garden incubation experiment. Forcing embryonic development at an extreme temperature (relative to current values) of 16° C, representing a future climate change scenario, significantly reduced survival compared to the more ecologically moderate temperature of 10° C (55% v. 93%). Survival at 14° C was intermediate between the other two temperatures (85%). More importantly, this survival response varied by provenance within and between temperature treatments. Thermal reaction norms showed an interacting response of genotype and environment (temperature), suggesting that populations of O. nerka may have adapted differentially to elevated temperatures during incubation and early development. Moreover, populations that historically experience warmer incubation temperatures at early development displayed a higher tolerance for warm temperatures. In contrast, thermal tolerance does not appear to transcend life stages as adult migration temperatures were not related to embryo thermal tolerance. The intra‐population variation implies potential for thermal tolerance at the species level. The differential inter‐population variation in thermal tolerance that was observed suggests, however, limited adaptive potential to thermal shifts for some populations. This infers that the intergenerational effects of increasing water temperatures may affect populations differentially, and that such thermally mediated adaptive selection may drive population, and therefore species, persistence.     

濒危植物蒙古扁桃不同地理种群遗传多样性的ISSR分析

采用 ISSR 分子标记对蒙古扁桃(Prunus mongolica)6个自然种群的遗传多样性进行了分析.12条ISSR引物共扩增出200条带,其中199条具多态性,多态位点比率为99.5％.在种群水平上多态位点百分率平均为55.3％.Nei's基因多样性、Shannon's信息指数在种群水平上分别为0.3241和0.4875,在物种水平上分别为0.3105和0.4722.根据基因分化系数,测得基因流值Nm为0.8266.UPGMA聚类分析结果表明:乌海千里沟种群和东升庙那仁乌拉种群遗传一致度最大,遗传关系最近.ISSR检测结果表明,包头萨拉齐种群的遗传多样性最丰富,在制定原位种质保护计划时,应优先保护包头萨拉齐周边地区的蒙古扁桃.     

Geographic variation in diapause induction and termination of the cotton bollworm, Helicoverpa armigera Hübner (Lepidoptera: Noctuidae)

Overwintering diapause in Helicoverpa armigera, a multivoltine species, is controlled by response to photoperiod and temperature. Photoperiodic responses from 5 different geographical populations showed that the variation in critical photoperiod for diapause induction was positively related to the latitudinal origin of the populations at 20, 22 and 25 °C. Diapause response to photoperiod and temperature was quite different between northern and southern populations, being highly sensitive to photoperiod in northern populations and temperature dependence in southern populations. Diapause pupae from southern population showed a significantly shorter diapause duration than from northern-most populations when they were cultured at 20, 22, 25, 28 and 31 °C; by contrast, overwintering pupae from southern populations emerged significantly later than from northern populations when they were maintained in natural conditions, showing a clinal latitudinal variation in diapause termination. Diapause-inducing temperature had a significant effect on diapause duration, but with a significant difference between southern and northern populations. The higher rearing temperature of 22 °C evoked a more intense diapause than did 20 °C in northern populations; but a less intense diapause in southern population. Cold exposure (chilling) is not necessary to break the pupal diapause. The higher the temperature, the quicker the diapause terminated. Response of diapause termination to chilling showed that northern populations were more sensitive to chilling than southern population.     

中国石榴栽培群体遗传多样性的荧光AFLP分析

以中国山东、安徽、陕西、河南、云南和新疆6个栽培石榴群体的85个品种类型为试材,利用荧光标记AFLP对中国石榴群体遗传多样性进行了研究。结果表明：8对引物组合在种级水平扩增的多态性位点数范围从135～185个不等,平均为158.25个,多态位点百分比范围为62.5%～86.11%,平均为73.26%,说明中国石榴品种遗传多样性较为丰富;石榴品种种级水平遗传多样性大于群体水平,6个群体的遗传多样性依次为河南群体〉新疆群体〉陕西群体〉安徽群体〉山东群体〉云南群体,并且具有显著性差异;群体间的遗传分化系数GST为0.2018,说明石榴遗传变异主要存在群体内,群体间的遗传变异占总变异的20.18%,根据基因分化系数,测得的基因流Nm为1.9027,说明中国石榴群体间存在适当的基因交流;UPGMA聚类分析结果表明,同一群体的大部分品种都聚在一起,但同时存在部分基因交流。所有遗传参数表明,中国石榴栽培品种遗传多样性较为丰富,其中河南群体遗传多样性显著高于其他群体,在中国石榴品种选育中具有更为广阔的应用前景。     

Temperature adaptation in a geographically widespread zooplankter,Daphnia magna

Evidence for temperature adaptation in Daphnia magna was inferred from variation in the shape of temperature reaction norms for somatic growth rate, a fitness‐related trait. Ex‐ephippial clones from eight populations across Europe were grown under standardized conditions after preacclimation at five temperatures (17–29 °C). Significant variation for grand mean growth rates occurred both within populations (among clones) and between populations. Genetic variation for reaction norm shape was found within populations, with temperature‐dependent trade‐offs in clone relative fitness. However, the population average responses to temperature were similar, following approximately parallel reaction norms. The among‐population variation is not evidence for temperature adaptation. Lack of temperature adaptation at the population level may be a feature of intermittent populations where environmentally terminated diapause can entrain the planktonic stage of the life‐history within a similar range of temperatures.