997 resultados para A. borealis d13C


Relevância:

10.00% 10.00%

Publicador:

Resumo:

Examination of hard parts recovered from scats (feces) is currently the most common method for determining the diet of pinnipeds. However, large or sharp prey remains may be spewed (regurgitated) biasing prey composition and size estimations in diet studies based on scats. Percent frequency of occurrence (FO%) and age or size of selected prey remains recovered from northern fur seal (Callorhinus ursinus) scat (n=3444) and spew samples (n=267) collected from rookeries on St. George Island and St. Paul Island, Alaska, between 1990 and 2000 were compared to determine if a bias in prey composition and age or size estimations existed between scats and spews. Overall prey composition was similar between sample type and location, but the relative FO% of primary prey (≥5%) varied by sample type and location. Age or size estimates of walleye pollock (Theragra chalcogramma) and of two species of gonatid squids (Gonatopsis borealis and Berryteuthis magister) were significantly larger in spews than in scats. Observed differences in FO% and estimated age or size of prey species whose remains were found in scats and spews likely result from size-selective digestion of prey remains. Scats were biased toward smaller prey remains, whereas spews were biased toward larger prey remains and cephalopod beaks. The percent overlap between age classes of walleye pollock caught by the commercial trawl fishery and age classes of walleye pollock consumed by northern fur seals varied noticeably between sample types for both islands (scats: St. George=15. 5%; St. Paul=4.1%; spews: St. George=94.6%; St. Paul=89.6%). These results demonstrate that the inclusion of multiple sampling methods allows for a more accurate assessment of northern fur seal prey occurrence and prey age and size.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

From December to February in most years from 1967 to 2007, observers counted gray whales, Eschrichtius robustus, from shore sites south of Carmel in central California. In addition to gray whales, other cetacean species were also recorded. These observations were summarized and compared among survey platforms and to ocean conditions. Eleven cetacean species were identified including eight odontocete species (killer whale, Orcinus orca; Pacific white-sided dolphin, Lagenorhynchus obliquidens; common dolphin, Delphinus spp.; bottlenose dolphin, Tursiops truncatus, northern right whale dolphin, Lissodelphis borealis; Risso’s dolphin, Grampus griseus; Dall’s porpoise, Phocoenoides dalli; and harbor porpoise, Phocoena phocoena) and three mysticete species (humpback whale, Megaptera novaeangliae; minke whale, Balaenoptera acutorostrata; and blue whale, Balaenoptera musculus). As expected, the detection of certain species among survey platforms (shore-based census watches, 25-power “Big Eye” binocular watches, and aerial surveys) was limited by species surfacing behavior and/or bathymetric preference. Comparisons among the shore-based census efforts showed a significant difference in sightings rates from 1967–84 (n = 14, mean = 0.11, SD = 0.11) to 1985–2007 (n = 11, mean = 1.48, SD = 0.47; t-Test: p < 0.001, df = 23). The warm period observed during the 1990’s may partially explain the increase in sighting rates and diversity of species observed at the census site compared to the much cooler temperatures of the 1970’s.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Estimates of incidental marine mammal, sea turtle, and seabird mortality in the California drift gillnet fishery for broadbill swordfish, Xiphias gladius, and common thresher shark, Alopias vulpinus, are summarized for the 7-year period, 1996 to 2002. Fishery observer coverage was 19% over the period (3,369 days observed/17,649 days fished). An experiment to test the effectiveness of acoustic pingers on reducing marine mammal entanglements in this fishery began in 1996 and resulted in statistically significant reductions in marine mammal bycatch. The most commonly entangled marine mammal species were the short-beaked common dolphin, Delphinus delphis; California sea lion, Zalophus californianus; and northern right whale dolphin, Lissodelphis borealis. Estimated mortality by species (CV and observed mortality in parentheses) from 1996 to 2002 is 861 (0.11, 133) short-beaked common dolphins; 553 (0.16, 103) California sea lions; 151 (0.25, 31) northern right whale dolphins; 150 (0.21, 27) northern elephant seals, Mirounga angustirostris; 54 (0.41, 10) long-beaked common dolphins, Delphinus capensis; 44 (0.53, 6) Dall’s porpoise, Phocoenoides dalli; 19 (0.60, 5) Risso’s dolphins, Grampus griseus; 11 (0.71, 2) gray whales, Eschrichtius robustus; 7 (0.83, 2) sperm whales, Physeter macrocephalus; 7 (0.96, 1) short-finned pilot whales, Globicephala macrorhychus; 12 (1.06, 1) minke whales, Balaenoptera acutorostrata; 5 (1.05, 1) fin whales, Balaenoptera physalus; 11 (0.68, 2) unidentified pinnipeds; 33 (0.52, 4) leatherback turtles, Dermochelys coriacea; 18 (0.57, 3) loggerhead turtles, Caretta caretta; 13 (0.73, 3) northern fulmars, Fulmarus glacialis; and 6 (0.86, 2) unidentified birds.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

白垩纪末至第三纪初(K/T界限,距今约65Ma,恐龙大规模灭绝,爬行类的优势地位被哺乳动物所取代;裸子植物和蕨类急剧衰退,被子植物蓬勃发展,并逐渐成为地表植被的主体,研究这一时期的植物群的结构和特征进而揭示植物演化和环境变迁的规律及其相互关系是当今地球科学、生命科学和环境科学的重要研究内容。黑龙江省嘉荫地区的乌云组产有丰富的植物化石,其地质时代虽未定论,但不超出晚白垩世马斯特里赫特期至早第三纪古新世的范围,处于K/T界限,对其植物群的研究意义重大。乌云植物群以往的研究在古果实学研究方面明显不足、在植物群的性质的认识及乌云组时代的确定等方面存在很大争议。本文重点研究了乌云组的果实和种子化石,增添了新的植物类群,丰富了此植物群的研究内容,对乌云组的时代问题的确定提供了新的证据。 本文研究了乌云组的Nordenskioldia borealis(昆兰树科)、Nyssidium jianyinense sp. nov. (连香树科)、Hypericum zhuii sp. nov. (金丝桃科)、Amersinia obtrullate(广义山茱萸科)、Acer wuyunense sp. nov.(槭树科)等5种果实和种子化石。Nordenskioldia borealis的果无柄、为分果、小果瓣环绕中央柱轮状排列。Nyssidium jianyinense的果序为圆锥果序、蓇葖对生、蓇葖腹缝相对、果皮三层。Hypericum zhuii的种子外形呈长椭圆形、端部具乳突、表面网状、种脊明显、种皮两层、外种皮细胞的垂周壁明显加厚。Amersinia obtrullate果序头状、果镘形、3果室。Acer wuyunense果为翅果、小坚果被明显侧翼、翅强烈下延,包围小坚果。经修订和补充,乌云植物群目前共有维管植物48属60种,其中,蕨类植物4属6种、裸子植物7属7种、被子植物37属48种,被子植物占总种数的80%、占总属数的77%,被子植物占绝对优势。当时的群落类型湿生群落和中生群落类型为主,湿生群落主要有:由SequoiaMetasequoiaTaxodium、Glyptostrobus等组成的针叶林;以Nyssidium、Trochodendroides占优势的阔叶林。 以Metasequoia优势的针叶林和以Nyssidium、Trochodendroides等占优势的阔叶林。乌云植物群中热带和亚热带成分占种子植物总属数的54%,而温带成分则占36%,亚热带成分占优势,当时的气候-植被类型为亚热带常绿林或常绿夏绿混交林。NordenskioldiaNyssidium、AmersiniaAcer化石的地质分布不早于古新世的地层,这—证据不支持乌云组的地质时代划为晚白垩世,而支持划归古新世的观点。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

早白垩世到早第三纪这段时期是松科早期起源和其后进行分支演化的关键时期。球果因为是重要的雌性生殖器官,而在松科演化问题上具有显著的研究价值。对早白垩世到早第三纪这段时间所发现的松科球果的研究经因一个半世纪的逐渐演变,现在划分为三个属:松属(Pinus),假南洋杉型属(Pseudoaraucaria,和松型球果属(Pityostrobus)。本文对采自辽宁义县早白垩世沙海组火山灰形成的凝灰质砂砾岩层中的一批硅化松科球果进行了详细的解剖学研究。将它们划分到松型球果属Pityostrobus中,并在此属下另立了4个新种:Pityostrobus hsuii, P. liaoningensis, P. yixianensis, P. borealis,以及五个暂时不能确切定种的类型。这些种以及类型根据鳞片基部树脂道的分布方式,划分为两类:一类包括Pityostrobus hsuii, P. liaoningensis,为在鳞片基部树脂道分布在鳞片迹的远轴面类型,它俩之间的区别主要在苞鳞复合体基部鳞片迹的形状上的显著差异,以及鳞片中上部树脂道的分布方式上的不同;另一类包括P. yixianensis以及与其相类似的四个类型和P. borealis以及一个与其相类似的类型,两个种在鳞片基部,树脂道分布在鳞片迹近轴面和远轴面,它们之间的差别主要在苞鳞复合体基部远轴面树脂道分布方式的不同而划分。通过与那些已发现的出产于欧洲和北美洲的种类进行对比,发现这批标本的结构性状上所体现出的多样性与欧美的标本有显著的不同。因此,在早白垩世,东亚为松科早期起源演化的一个重要中心。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Adaptive cluster sampling (ACS) has been the subject of many publications about sampling aggregated populations. Choosing the criterion value that invokes ACS remains problematic. We address this problem using data from a June 1999 ACS survey for rockfish, specifically for Pacific ocean perch (Sebastes alutus), and for shortraker (S. borealis) and rougheye (S. aleutianus) rockfish combined. Our hypotheses were that ACS would outperform simple random sampling (SRS) for S. alutus and would be more applicable for S. alutus than for S. borealis and S. aleutianus combined because populations of S. alutus are thought to be more aggregated. Three alternatives for choosing a criterion value were investigated. We chose the strategy that yielded the lowest criterion value and simulated the higher criterion values with the data after the survey. Systematic random sampling was conducted across the whole area to determine the lowest criterion value, and then a new systematic random sample was taken with adaptive sampling around each tow that exceeded the fixed criterion value. ACS yielded gains in precision (SE) over SRS. Bootstrapping showed that the distribution of an ACS estimator is approximately normal, whereas the SRS sampling distribution is skewed and bimodal. Simulation showed that a higher criterion value results in substantially less adaptive sampling with little tradeoff in precision. When time-efficiency was examined, ACS quickly added more samples, but sampling edge units caused this efficiency to be lessened, and the gain in efficiency did not measurably affect our conclusions. ACS for S. alutus should be incorporated with a fixed criterion value equal to the top quartile of previously collected survey data. The second hypothesis was confirmed because ACS did not prove to be more effective for S. borealis-S. aleutianus. Overall, our ACS results were not as optimistic as those previously published in the literature, and indicate the need for further study of this sampling method.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

A new species Norileca borealis belonging to the family Cymothoidae is described in detail and illustrated. The new species is distinguished from the other members of the genus by the details of maxilla 2, maxilliped, pleotelson and pereopod 1.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

海拔梯度造成的环境异质性,如崎岖的地形、复杂的植被结构以及花期延迟等可能会极大地影响到物种的形态和遗传变异格局。理解物种形态和遗传变异的海拔格局对于物种多样性的管理和保护是非常重要的。尽管植物群体遗传学是一个飞速发展的研究领域,然而与海拔相关的形态变异、遗传变异及群体间遗传差异的研究却很少。到目前为止,还不清楚遗传变异与海拔之间是否必然的相关性。 川滇高山栎是一种重要的生态和经济型树种,广泛分布于中国西南的四川、西藏、贵州和云南省的高海拔地区,在保持水土、调节气候方面起着十分重要的作用。尽管主要受阳光限制而仅分布于阳坡,但其海拔梯度范围较大,表明川滇高山栎对不同的环境具有很强的适应性。本文通过叶型及生理响应、微卫星分子标记和扩增性片段长度多态性方法,试图探索川滇高山栎叶沿海拔梯度的形态和生理响应及其沿海拔梯度的遗传变异格局,为川滇高山栎的保护和利用提供进一步的遗传学理论依据和技术指导。 对叶形、含氮量及碳同位素的试验结果表明,平均比叶面积、气孔密度、气孔长度和气孔指数等气孔参数随海拔的升高呈非线性变化。在海拔大于2800 m时,川滇高山栎的比叶面积、气孔长度和气孔指数都随海拔升高而降低,但是在海拔小于2800 m时,这些指标都随海拔的升高而增大。相对而言,单位叶面积的含氮量和碳同位素则表现出相反的变化模式。另外,比叶面积是决定碳同位素沿海拔梯度变化的最重要参数。本研究结果表明,海拔2800 m附近是川滇高山栎生长和发育的最适地带,在这里生长的植物叶片厚度更薄、气孔更大、叶碳同位素值更小。 利用六对微卫星引物对五个不同海拔川滇高山栎群体遗传多样性进行研究,结果表明,群体内表现出较高的遗传多样性,平均每位点等位基因数11.33个,平均期望杂合度达0.820。群体间差异较小,分化仅为6.6%。聚类分析也并没有显示出明显的海拔格局。然而低频率等位基因却与海拔呈显著性正相关(R2=0.97, P < 0.01),表明在高海拔处,川滇高山栎以更多的稀有基因来适应恶劣的环境条件。本试验结果表明由海拔梯度形成的选择性压力对川滇高山栎群体的遗传变异影响并不明显。 为了进一步探讨川滇高山栎群体遗传变异与海拔之间的相互关系,我们还对其进行了扩增性片段长度多态性分析。结果表明:(1)随海拔的升高(从群体WL2到群体WL5),群体内遗传变异降低,而群体间遗传差异增加;(2)低海拔群体WL1表现出最低的遗传变异性(HE = 0.181),同时与其余四个群体间呈现出最大的遗传差异性(平均FST = 0.0596);(3)在除去低海拔群体WL1后,Mantel检测表明群体间遗传距离与海拔距离之间表现出正相关性。另外,研究结果还表明,遗传变异受生境条件(过度的湿热环境)及人为干扰(火烧、砍伐和放牧)的影响,这一点至少在低海拔群体WL1上发生了作用。 通过叶形态、生理及DNA子水平的研究,结果表明叶形态特征和碳同位素与海拔紧密相关,与海拔之间呈非线性变化,海拔2,800 m附近是川滇高山栎生长和发育的最适地带。海拔梯度在一定程度上会影响到川滇高山栎群体的遗传变异结构,但在这样一个狭窄的地理分布区域里,这种影响并不足以导致群体间较大的遗传分化。同时生境条件及人为干扰也是影响遗传变异的限制性因子,不容忽视。 Altitudinal gradients impose heterogeneous environmental conditions, such as rugged topography, a complex pattern of vegetation and flowering delay, and they likely furthermore markedly affect the morphological and genetic variation pattern of a species. Understanding altitudinal pattern of morphological and genetic variation at a species is important for the management and conservation of species diversity. Although plant population genetics is a fast growing field of research, there are only few recent investigations, which analyzed the genetic differentiation and changes of intra-population variation along altitudinal gradients. At present, it is still unclear whether there are some common patterns of morphological and genetic variation with altitude. Quercus aquifolioides Rehder & E.H. Wilson, which is an important ecological and economical endemic woody plant species, is widely distributed in the Yunnan and Sichuan provinces, Southwest China. Its large range of habitat across different altitudes implies strong adaptation to different environments, although it is mainly restricted to sunny, south facing slopes. It plays a very important role in preventing soil erosion, soil water loss and regulating climate, as well as in retaining ecological stability. In this paper, we tried to understand the altitudinal pattern of morphological and genetic variation along altitudinal gradients through the experiments of leaf morphological and physiological responses, microsatellite analysis and AFLP markers. In leaf morphological and physiological responses experiment, we measured leaf morphology, nitrogen content and carbon isotope composition (as an indicator of water use efficiency) of Q. aquifolioides along an altitudinal gradient. We found that these leaf morphological and physiological responses to altitudinal gradients were non-linear with increasing altitude. Specific leaf area, stomatal length and index increased with increasing altitude below 2,800 m, but decreased with increasing altitude above 2,800 m. In contrast, leaf nitrogen content per unit area and carbon isotope composition showed opposite change patterns. Specific leaf area seemed to be the most important parameter that determined the carbon isotope composition along the altitudinal gradient. Our results suggest that near 2,800 m in altitude could be the optimum zone for growth and development of Q. aquifolioides, and highlight the importance of the influence of altitude in research on plant physiological ecology. Genetic variation and differentiation were investigated among five natural populations of Q. aquifolioides occurring along an altitudinal gradient that varied from 2,000 to 3,600 m above sea level in the Wolong Natural Reserve of China, by analyzing variation at six microsatellite loci. The results showed that the populations were characterized by relatively high intra-population variation with the average number of alleles equaling 11.33 per locus and the average expected heterozygosity (HE) being 0.779. The amount of genetic variation varied only little among populations, which suggests that the influence of altitude factors on microsatellite variation is limited. However, there is a significantly positive correlation between altitude and the number of low-frequency alleles (R2=0.97, P < 0.01), which indicates that Q. aquifolioides from high altitudes has more unique variation, possibly enabling adaptation to severe conditions. F statistics showed the presence of a slight deficiency of heterozygosity (FIS=0.136) and a low level of differentiation among populations (FST=0.066). The result of the cluster analysis demonstrates that the grouping of populations does not correspond to the altitude of the populations. Based on the available data, it is likely that the selective forces related to altitude are not strong enough to significantly differentiate the populations of Q. aquifolioides in terms of microsatellite variation. To further elucidate genetic variation pattern of Q. aquifolioides populations under sub-alpine environments, genetic variation and differentiation were investigated along altitudinal gradients using AFLP markers. The altitudinal populations with an average altitude interval of 400 m, i.e. WL1, WL2, WL3, WL4 and WL5, correspond to the altitudes 2,000, 2,400, 2,800, 3,200 and 3,600 m, respectively. Our results were as follows: (i) decreasing genetic variation (ranging from 0.253 to 0.210) and increasing genetic differentiation with altitude were obtained from the WL2 to the WL5 population; (ii) the WL1 population showed the lowest genetic variation (HE = 0.181) and the highest genetic differentiation (average FST = 0.0596) with the other four populations; (iii) the positive correlation was obtained using Mantel tests between genetic and altitude distances except for the WL1 population. Our results suggest that altitudinal gradients may have influenced the genetic variation pattern of Q. aquifolioides populations to some extent. In addition, habitat environments (unfavorable wet and hot conditions) and human disturbances (burning, grazing and felling) were possible influencing factors, especially to the low-altitude WL1 population. The present study shows that there were close correlations between morphological features and carbon isotope composition in our data. This indicates that a coordinated plant response modified these parameters simultaneously across different altitudes. Around 2,800 m altitude there seems to be an optimum zone for growth and development of Q. aquifolioides, as indicated by thinner leaves, larger stomata and more negative d13C values. All available evidence indicates altitudinal gradients may have influenced the genetic variation pattern of Q. aquifolioides to some extent. Decreasing genetic variation and increasing genetic differentiation with altitude was obtained except for the WL1 population. And the environment of habitats and human disturbances were also contributing factors, which impact genetic variation pattern, especially to the low-altitude WL1 population.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

介绍了蜡革菌属Ceraceomyces及该属在中国的种类,其中北方蜡革菌Ceraceomyces borealis是中国新记录种,根据中国的材料对其进行了详细的描述和显微结构绘图,同时给出了中国蜡革菌属5个种的检索表。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

本文综合了中国北方孔达岩系和石墨矿床的碳同位素数据102件, 发现片麻岩石墨n 透辉岩石墨< 大理岩石墨<石墨大理岩方解石< 大理岩方解石; 混合岩化岩石中石墨D13C 总介于有机碳和无机碳之间; 不同地体片麻岩石墨D13C 极为一致, 变化于- 22. 8‰~ - 21. 48‰, 略低于世界有机质平均值- 26 ±7‰; 大理岩的原岩碳酸盐D13C 高于2‰, 与2330~ 2060Ma间全球性D13Ccarb 正向漂移事件一致。地质流体是碳同位素分馏、均一化的重要因素, 是石墨矿床的3种主要碳源之一, 是碳的5 种存在形式之一, 也是碳循环的重要媒介和方式; 导致热液矿床D13C= - 5‰左右的因素较多, 依据D13Ccalciteµ - 5‰得出成矿物质和流体来自地幔的结论值得怀疑; 中国北方孔达岩系形成于古元古代, 可能为2300~ 2050Ma

Relevância:

10.00% 10.00%

Publicador:

Resumo:

测定了贵州喀斯特山区灌丛12 种主要植物叶片的D13C 值, 研究了植物叶片碳同位素组成特征, 并分析了植物的水分利用效率。结果表明: 该区植物叶片的碳同位素组成的变化范围为- 26. 98‰~ - 29. 15‰, 平均值为- 28. 14‰。研究区D13C 值的分布相对均匀, 除高于我国热带雨林区植物外, 低于其它地区。此外, 植物的碳同位素组成存在较大的种间差异, 生境的变化对植物的碳同位素组成有着一定的影响, 但不同植物种对生境的响应不同。植物的D13C 值从生长初期到末期有降低的趋势, 但不同植物种的变化趋势存在差异。植物D13C 值随海拔的增加而增大, 但不同植物种D13C 值随海拔增加的程度存在差异。不同植物种之间的水分利用效率不同, 相同植物种在不同的生境条件下其水分利用效率也有差异。植物生长初期的水分利用效率要比后期的高; 高海拔处植物水分利用效率要比低海拔处植物的高。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The main success of my thesis has been to establish the mechanism by which antifreeze proteins (AFPs) bind irreversibly to ice crystals, and hence prevent their growth. AFPs organize ice-like water on their ice-binding site, which then merges and freezes with the quasi-liquid layer of ice. This was revealed from studying the exceptionally large (ca. 1.5-MDa) Ca 2+-dependent AFP from the Antarctic bacterium Marinomonas primoryensis (MpAFP). The 34-kDa antifreeze- active region of MpAFP was predicted to fold as a novel Ca 2+-binding β-helix. Site-directed mutagenesis confirmed the model and demonstrated that its ice-binding site (IBS) consisted of solvent-exposed Thr and Asx parallel arrays on the Ca 2+-binding turns. The X-ray crystal structure of the antifreeze region was solved to a resolution of 1.7 Å. Two of the four molecules within the unit cell of the crystal had portions of their IBSs freely exposed to solvent. Identical clathrate-like cages of water molecules were present on each IBS. These waters were organized by the hydrophobic effect and anchored to the protein via hydrogen bonds. They matched the spacing of water molecules in an ice lattice, demonstrating that anchored clathrate waters bind AFPs to ice. This mechanism was extended to other AFPs including the globular type III AFP from fishes. Site-directed mutagenesis and a modified ice-etching technique demonstrated this protein uses a compound ice-binding site, comprised of two flat and relatively hydrophobic surfaces, to bind at least two planes of ice. Reinvestigation of several crystal structures of type III AFP identified anchored clathrate waters on the solvent-exposed portion of its compound IBS that matched the spacing of waters on the primary prism plane of ice. Ice nucleation proteins (INPs), which can raise the temperature at which ice forms in solution to just slightly below 0oC, have the opposite effect to AFPs. A novel dimeric β-helical model was proposed for the INP produced by the bacterium Pseudomonas borealis. Molecular dynamics simulations showed that INPs are also capable of ordering water molecules into an ice- like lattice. However, their multimerization brings together sufficient ordered waters to form an ice nucleus and initiate freezing.