49 resultados para Sympatric prey


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Summer diets of two sympatric raptors Upland Buzzards (Buteo hemilasius Temminck et Schlegel) and Eurasian Eagle Owls (Bubo bubo L. subsp. Hemachalana Hume) were studied in an alpine meadow (3250 m a.s.l.) on Qinghai-Tibet Plateau, China. Root voles Microtus oeconomus Pallas, plateau pikas Ochotona curzoniae Hodgson, Gansu pikas O. cansus Lyon and plateau zokors Myospalax baileyi Thomas were the main diet components of Upland Buzzards as identified through the pellets analysis with the frequency of 57, 20, 19 and 4%, respectively. The four rodent species also were the main diet components of Eurasian Eagle Owls basing on the pellets and prey leftovers analysis with the frequency of 53, 26, 13 and 5%, respectively. The food niche breadth indexes of Upland Buzzards and Eurasian Eagle Owls were 1.60 and 1.77 respectively (higher value of the index means the food niche of the raptor is broader), and the diet overlap index of the two raptors was larger (C-ue = 0.90) (the index range from 0 - no overlap - to I - complete overlap). It means that the diets of Upland Buzzards and Eurasian Eagle Owls were similar (Two Related Samples Test, Z = -0.752, P = 0.452). The classical resource partitioning theory can not explain the coexistence of Upland Buzzards and Eurasian Eagle Owls in alpine meadows of Qinghai-Tibet Plateau. However, differences in body size, predation mode and activity rhythm between Upland Buzzards and Eurasian Eagle Owls may explain the coexistence of these two sympatric raptors.

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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.

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Very little is known about how global anthropogenic changes will affect major harmful algal bloom groups. Shifts in the growth and physiology of HAB species like the raphidophyte Heterosigma akashiwo and the dinoflagellate Prorocentrum minimum due to rising CO2 and temperature could alter their relative abundance and environmental impacts in estuaries where both form blooms, such as the Delaware Inland Bays (DIB). We grew semi-continuous cultures of sympatric DIB isolates of these two species under four conditions: (1) 20 degrees C and 375 ppm CO2 (ambient control), (2)20 degrees C and 750 ppm CO2 (high CO2),(3) 24 degrees C and 375 ppm CO2 (high temperature), and (4) 24 degrees C and 750 ppm CO2 (combined). Elevated CO2 alone or in concert with temperature stimulated Heterosigma growth, but had no significant effect on Prorocentrum growth. P-Bmax (the maximum biomass-normalized light-saturated carbon fixation rate) in Heterosigma was increased only by simultaneous CO2 and temperature increases, whereas P-Bmax in Prorocentrum responded significantly to CO2 enrichment, with or without increased temperature. CO2 and temperature affected photosynthetic parameters alpha, Phi(max), E-k, and Delta F/F'(m) in both species. Increased temperature decreased and increased the Chl a content of Heterosigma and M Prorocentrum, respectively. CO2 availability and temperature had pronounced effects on cellular quotas of C and N in Heterosigma, but not in Prorocentrum. Ratios of C:P and N:P increased with elevated carbon dioxide in Heterosigma but not in Prorocentrum. These changes in cellular nutrient quotas and ratios imply that Heterosigma could be more vulnerable to N limitation but less vulnerable to P-limitation than Prorocentrum under future environmental conditions. In general, Heterosigma growth and physiology showed a much greater positive response to elevated CO2 and temperature compared to Prorocentrum, consistent with what is known about their respective carbon acquisition mechanisms. Hence, rising temperature and CO2 either alone or in combination with other limiting factors could significantly alter the relative dominance of these two co-existing HAB species over the next century. (c) 2007 Elsevier B.V. All rights reserved.

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兰科植物精巧的花部结构及其独特的传粉机制为自然选择理论和异花受粉优势学说提供了强有力的证据。开展兰科植物的传粉生态学研究对进一步探讨植物进化中的一些关键问题(如生殖隔离、物种形成、适应和繁育系统进化等)具有重要意义。本文通过对独花兰 (Changnienia amoena) 和扇脉杓兰 (Cypripedium japonicum) 两种兰科植物进行植物与传粉者之间关系、种内形态变异、花粉散布等方面的研究,探讨其适应进化方式、传粉系统的进化趋势,同时为开发适用的分子标记,在独花兰中初步摸索和探讨了微卫星标记的分离。主要研究结果如下: 1. 濒危植物独花兰的传粉生态学 在神农架2个地点进行了连续2年的野外观测和实验。结果表明,独花兰是一种自交亲和、需要昆虫传粉的欺骗性植物。在2个地点独花兰的传粉者种类不同,在龙门河三条熊蜂 (Bombus (Diversobombus) trifasciatus) 是主要传粉者,在关门山仿熊蜂 (B. (Tricornibombus) imitator) 是唯一的传粉者。尽管它们出现的丰度和觅食行为不同,但其传粉行为和携粉部位非常相同,因此,可以看作是一个功能群(functional group)。从种群水平上看,开花个体的分布式样不是显著的偏斜曲线图,传粉者的有效访问主要集中在开花的前、中期。由于没有花蜜,传粉者在花内停留的时间很短,花粉块输出和传粉发生在熊蜂劳而无获的访问、退出花时。自然条件下,独花兰的结实率很低,只有6%-12%,并呈现明显的年份和地点变化。传粉者限制是结实率低的主要原因。与同亚族近缘种布袋兰相比,分布于中国中部的独花兰受冰期的影响很小,其传粉环境相对稳定,在进化历史中,形成了一种稳定的传粉系统。本研究结果纠正了前人对独花兰繁殖方式的错误认识,并为其保护策略的制订提供了重要资料。 2. 独花兰种群大小、传粉者访问和花粉流 为了检验独花兰种群大小、空间格局与传粉者访问之间的关系,连续2年对10个独花兰种群的花粉块输出和输入进行了统计分析,同时对花粉块进行标记研究其散布式样。结果显示,花粉块输出比例与种群大小之间关系在2003年呈显著负相关,但在2004年这种负相关关系不显著。尽管独花兰的空间分布格局在不同种群不同,但传粉者的访问除了在有蜂巢的种群为聚集式访问外,其余种群内均为随机访问式样。花粉块的散布式样呈尖峰态分布,多数花粉块散布很短的距离,少数散布较远。花粉块的平均散布距离在龙门河为7.3 m,在关门山为10.6 m。由于各种群之间相隔很远,种群之间花粉块交流受到限制,很少有种群外的花粉块输入。花粉块传递只在种群内近缘个体中进行,有可能导致种内遗传或形态分化。 3. 独花兰种内形态变异及其适应意义 对庐山、新宁和神农架3个地点15个独花兰自然种群的形态变异进行了研究,探讨了形态多样性水平和地理变异式样及其可能的适应机制。结果表明,在物种水平上独花兰形态性状存在丰富的变异。单因素方差分析显示3个地区间多个形态性状存在极显著差异(P<0.01),UPGMA聚类分析也表明这3个地区分别形成明显不同的分支,说明3个地区种群植物形态已经出现分化。在神农架地区,龙门河和关门山两个地点间出现明显的形态分化,而这两个地点的传粉者在形体大小表现出显著差异。适合度与形态性状之间的相关性分析显示,独花兰种内形态分化是以传粉者为媒介的自然选择作用的结果。移栽实验显示,本地传粉者对本地和移栽种群花的访问表现出一定的选择性。 4. 扇脉杓兰的传粉生态学研究 与独花兰同域分布、花期不遇的扇脉杓兰是杓兰属的一个特殊类群,具有典型“Japonicum”型唇瓣类型。对神农架6个种群连续两年野外观测和实验结果表明,扇脉杓兰是一种自交亲和、需要昆虫传粉的欺骗性植物。在种群水平上开花个体的分布式样呈显著的偏斜曲线图,在短时间内迅速到达盛花期。扇脉杓兰的传粉者是三种熊蜂,其访问频次很低,访问时间很短,有效访问主要集中在开花的前、中期。自然结实率只有4.3%-8.5%,人工授粉实验证明,传粉者限制是结实率低的主要原因,且传粉者限制程度在花期不同阶段和不同地点存在差异。对欺骗性植物聚集生长、开花有利于吸引传粉者这一假说进行检验,结果显示,克隆群丛大小与传粉者有效访问(花粉块输出比例)呈弱负相关关系。聚集生长的结实率与分散生长的没有显著差异,说明繁殖成功与开花个体的密度无关。扇脉杓兰的花粉集结为未蜡质化的花粉块,是杓兰属中粘质花粉和蜡质花粉块的中间进化类型。传粉生态学和形态学证据显示C. acaule和扇脉杓兰是东亚-北美间断分布的姐妹种对。 5. 独花兰微卫星位点的分离 为了深入研究独花兰种群的基因流和交配系统,用Dynabeads和选择性杂交法分离微卫星位点、筛选引物。首先将基因组DNA用合适的内切酶消化为400-1000 bp大小的片段,然后用生物素标记的简单重复寡核苷酸序列做探针与其杂交,杂交复合物用抗生链霉素蛋白包裹的磁珠吸附,经过一系列洗脱、沉淀,得到富含重复片段的DNA,然后在进行克隆、测序,利用SSR两侧翼区设计引物,经过多态性分析可得到微卫星标记。结果显示,35个克隆序列中18个(51.4%)含有重复片段(SSRs),说明用Dynabeads富集效率明显高于传统方法。到目前为止所得引物共4对。这一实验方法的探索为以后分离杓兰属等兰科植物微卫星位点、进而进行群体遗传学研究奠定了一定的基础。

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兰科植物是被子植物中物种最丰富和最进化的类群之一,具有精巧、多样化的花部结构以及独特的吸引传粉者方式。开展兰科植物传粉生物学的研究对理解自然选择机制和异花授粉优势学说具有重要的理论意义。广西雅长兰科植物自然保护区是我国第一个以兰科植物命名的保护区,本文通过对保护区内同域分布的流苏贝母兰(Coelogyne fimbriata)和兔耳兰(Cymbidium lancifolium )传粉过程观察和繁殖成功等方面的研究,探讨兰科植物传粉机制和防止同株异花授粉的机制。同时结合传粉生物学研究的结果,对兰科植物多样性保护提出相关建议。主要研究结果如下: 1.流苏贝母兰的传粉生物学 在保护区2 个居群内对流苏贝母兰花期物候、传粉者种类和行为进行了连续3 年(2005-2007)的观察,对花和传粉者形态学指标进行了测量,对两个居群内所选取实验样地的花粉移走率、花粉接收率和结实率进行了详细的统计,通过动物行为学实验检测了花香对传粉者吸引方面的影响。并通过人工繁育系统实验检测流苏贝母兰的繁殖特征。结果显示,流苏贝母兰为具有特殊气味且无花蜜的兰科植物,由一种黄胡蜂属(Vespula)昆虫的雌性个体专性传粉,此为第二例由胡蜂专性传粉的具有食源性欺骗机制的兰科植物,且在传粉者行为和吸引机制与第一例存在很大差异。行为学实验显示花香对传粉者具有吸引作用。流苏贝母兰的花期与实验地黄胡蜂的繁殖季节和种群扩张期相吻合,在此期间,为了满足自身和幼虫的需求,黄胡蜂对碳水化合物需求大大增加。推测流苏贝母兰利用了黄胡蜂在繁殖和种群扩张期间需要大量摄取碳水化合物类物质,通过模拟碳水化合物来源(如果实或有花蜜、汁液分泌的植物)的气味,吸引传粉者。居群内花粉移走率、花粉接收率和结实率分别为0.069-0.918,0.025-0.695和0.014-0.069。结实率较低的原因可能与流苏贝母兰的自交不亲和特性和传粉者连续访问造成的同克隆授粉有关。其自交不亲和特性能有效地阻止自交,促进异交,同时蕊喙在接收花粉24 h 内与柱头愈合也能够减少花粉浪费,提高雄性适合度。 2.兔耳兰的传粉生物学 在保护区1 个居群内对兔耳兰进行了连续2 年(2005-2006)的观察和实验。观察发现兔耳兰唯一的传粉者为膜翅目蜜蜂科的中华蜜蜂(Apis cerana cerana)。中华蜜蜂在花内的停留时间为8-71 s。根据观察我们推测兔耳兰可能是通过其唇瓣上无规则的紫栗色小斑点(假蜜导)来吸引中华蜜蜂为其传粉, 属于食源性欺骗方式。在传粉过程中兔耳兰的药帽与花粉团和粘盘一起粘在中华蜜蜂胸背部。药帽的存在能够阻止下一朵被拜访的花实现雌性功能。兔耳兰药帽高度加上传粉昆虫胸高大于传粉通道入口的高度, 支持兔耳兰可能通过药帽来减少同株异花授粉现象的推测。蕊喙会在花粉接受72 h 内逐渐下弯并与柱头愈合,将接受的花粉包裹,且有些花的花萼片和侧面的两个花瓣会环抱住唇瓣侧裂片及蕊柱形成的入口,即传粉通道,避免继续接收花粉,增加花粉输出,提高雄性适合度。2005 和2006 年该兔耳兰居群的自然繁殖成功率分别为0.211 和0.213。繁育系统实验证明兔耳兰是高度自交亲和物种,不存在无融合生殖和自动自花授粉的现象, 其结实依赖传粉者。TTC 法检测结果显示兔耳兰种子活力达85.78%因此推断种子活力不是制约兔耳兰种子萌发的主要原因。而传粉者的密度和访问频率可能是影响兔耳兰结实的重要因素, 并最终影响兔耳兰种群的维持和扩张。 3.兰科植物促进繁殖成功的机制 植物通过各种方式吸引传粉者的最终目的是实现繁殖成功,是植物生活史的重要环节。兰科植物具有雌雄同体的合蕊柱的特殊结构,为了避免花粉-柱头间的干扰,其进化出一系列特殊的花部结构和适应机制,如欺骗性吸引机制、花粉块柄弯曲、花粉干缩等等。流苏贝母兰作为大量开花的克隆植物,其自交不亲和特性是促进异交的重要机制,另外蕊喙在花粉接收24 h 内与柱头发生愈合也是减少同株异花授粉机率的重要花部适应特征。兔耳兰为聚丛状生长的兰科植物,总状花序具多朵花,在传粉过程中通过药帽的阻挡和机械隔离,使携带于昆虫背部的花粉不能进入花内与柱头发生接触,避免同株异花授粉的发生。另外兔耳兰也存在花部适应的机制,蕊喙在花粉接收72 h 内逐渐下弯与柱头愈合,同时有些花的花萼片和侧面的两个花瓣环抱传粉通道入口,避免继续接收花粉,提高雄性适合度。 4. 兰科植物传粉系统和多样性保护 传粉生物学的研究为兰科植物的保护生物学提供了坚固的理论基础和重要的科学依据。绝大部分的兰科植物繁殖成功受到传粉者数量的限制。由于其精巧的花部结构,约67%已知传粉系统的兰科植物仅由唯一的传粉者专性传粉。另外,在某些区域内,还存在着较高程度的传粉者共享。传粉者数量的减少已经威胁到兰科植物的繁殖生存。因此,对兰科植物的保护应不仅仅关注于植物的保护,同时还应致力于传粉系统的保护。

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Leptobrachium ailaonicum is a vulnerable anuran restricted to a patchy distribution associated with small mountain streams surrounded by forested slopes at mid-elevations (approximately 2000-2600 m) in the subtropical Mount Wuliang and Mount Ailao ranges in southwest China (Yunnan Province) and northern Vietnam. Given high habitat specificity and lack of suitable habitat in lower elevations between these ranges, we hypothesized limited gene flow between populations throughout its range. We used two mitochondrial genes to construct a phylogeographic pattern within this species in order to test our hypothesis. We also examined whether this phylogeographic pattern is a response to past geological events and/or climatic oscillations. A total of 1989 base pairs were obtained from 81 individuals of nine populations yielding 51 unique haplotypes. Both Bayesian and maximum parsimony phylogenetic analyses revealed four deeply divergent and reciprocally monophyletic mtDNA lineages that approximately correspond to four geographical regions separated by deep river valleys. These results suggest a long history of allopatric separation by vicariance. The distinct geographic distributions of four major clades and the estimated divergence time suggest spatial and temporal separations that coincide with climatic and paleogeographic changes following the orogeny and uplift of Mount Ailao during the late Miocene to mid Pliocene in southwest China. At the southern distribution, the presence of two sympatric yet differentiated clades in two areas are interpreted as a result of secondary contact between previously allopatric populations during cooler Pleistocene glacial cycles. Analysis of molecular variance indicates that most of the observed genetic variation occurs among the four regions implying long-term interruption of maternal gene flow, suggesting that L ailaonicum may represent more than one distinct species and should at least be separated into four management units corresponding to these four geographic lineages for conservation. (C) 2009 Elsevier Inc. All rights reserved.

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Bamboo bats are a group of small bats with unique skull and morphology. They roost inside hollow bamboo stems in tropical and subtropical Asia and the Ambon Islands (Moluccas). We examined 53 specimens of Tylonycteris from southern and southwestern China. Comparisons of skull and external characteristics, pelage color, shapes of thumbpads and footpads, and statistical analysis of cranial measurements revealed that specimens from Damenglong, Jinghong County, Xishuang-banna, Yunnan, are distinctly different from the other two species of Tylonycteris described so far. The Yunnan specimens are the smallest in size; have dark blackish brown pelage color; and have larger upper premolars, smaller first lower premolars, and longer C-M-3. They are sympatric with the previously described species. Here we review the genus Tylonycteri and describe a new species, Tylonycteris pygmaeus, from the Yunnan material.

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Rhesus macaques and stump-tailed macaques are sympatric in western Yunnan (China), coexisting or occupying habitats that show little difference. This paper tests hypotheses based on theoretical expectation from the differing biomechanical demands of terrestrial and arboreal quadrupedalism in stump-tailed macaques and rhesus macaques, respectively. Individuals of these two macaque taxa were markedly separated by the first two principal components and discriminant analyses based on 18 variables of the upper limb. The rhesus macaques appear to be more adapted for arboreal quadruped habits because of elongation of the clavicle and forearm, a larger humeral head and greater midshaft sagittal diameters of the radius and ulna.

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In this paper the habitat structure and ecology of Presbytis francoisi and Presbytis leucocephalus are compared. Observations were made of the two langur species in areas of southwest Guangxi province in which the langurs occur but are not sympatric. The results showed that the habitat of P. leucocephalus differs from that of P. francoisi and that the habitat in western areas was different from that in eastern areas in terms of vegetation and other criteria. P. francoisi was limited in its distribution to localities at higher altitudes, in contrast to P. leucocephalus. This may be due to human activities such as crop cultivation and logging. With respect to its activity pattern, P. leucocephalus spent 51.8% of its day in the trees and 48.2% on the rocky substrate. The results of this study suggest that Presbytis may best be regarded as a semiarboreal form.

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The Yangtze finless porpoise (Neophocaena phocaenoides asiaeorientalis) is currently limited to the middle and lower reaches of the Yangtze River from Yichang to Shanghai, China, and the adjoining Poyang and Dongting Lakes. Its population size has decreased remarkably during the last several decades due to the heavy impact of human activities, including overfishing of prey species, water development projects that cause attendant habitat loss and degradation, water pollution, and accidental deaths caused by harmful fishing gear and collisions with motorized vessels. It was estimated that the number of remaining individuals was down to approximately 1800 in 2006, a number that is decreasing at a rate as high as 5% per year. Three conservation measures - in situ and ex situ conservation and captive breeding have been applied to the protection of this unique porpoise since the early 1990s. Seven natural and two "semi-natural" reserves have so far been established. Since 1996, a small group of finless porpoises has been successfully reared in a facility at the Institute of Hydrobiology of the Chinese Academy of Sciences; three babies were born in captivity on July 5, 2005, June 2, 2007 and July 5, 2008. These are the first freshwater cetaceans ever born in captivity in the world. Several groups of these porpoises caught in the main stream of the Yangtze River, or rescued, have been introduced into the Tian'e-Zhou Semi-natural Reserve since 1990. These efforts have proven that, not only can these animals survive in the area, they are also to reproduce naturally and successfully. More than 30 calves had been born in the reserve since then, with one to three born each year. Taking deaths and transfers into account, there were approximately 30 individuals living in the reserve as of the end of 2007. Among eight mature females captured in April 2008, five were confirmed pregnant. This effort represents the first successful attempt at off-site protection of a cetacean species in the world, and establishes a solid base for conservation of the Yangtze finless porpoise. A lesson must be drawn from the tragedy of Chinese River Dolphin (Lipotes vexillifer), which has already been declared likely extinct. Strong, effective and appropriate protective measures must be carried out quickly to prevent the Yangtze finless porpoise from becoming a second Chinese River Dolphin, and save the biodiversity of the Yangtze River as a whole.

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A 2-year investigation of growth and food availability of silver carp and bighead was carried out using stable isotope and gut content analysis in a large pen in Meiliang Bay of Lake Taihu, China. Both silver carp and bighead exhibited significantly higher delta 13C in 2005 than in 2004, which can probably be attributed to two factors: (i) the difference between isotopic compositions at the base of the pelagic food web and (ii) the difference between the compositions of prey items and stable isotopes. The significantly positive correlations between body length, body weight and stable isotope ratios indicated that isotopic changes in silver carp and bighead resulted from the accumulation of biomass concomitant with rapid growth. Because of the drastic decrease in zooplankton in the diet in 2005, silver carp and bighead grew faster in 2004 than in 2005. Bighead carp showed a lower trophic level than silver carp in 2005 as indicated by stable nitrogen isotope ratios, which was possibly explained by the interspecific difference between the prey species and the food quality of silver carp and bighead.

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Stringency in the identification of conspecific call properties is essential among sympatric species to ensure conspecific mating, as the risk of improper recognition and heterospecific mating is high. In this study we investigated the basic signal structure required for intraspecies communication in the Chinese alligator (Alligator sinensis), a species that has no relatives living in sympatry, by playback of signals modified in the temporal (truncating original bellows with first 1/4, 1/2, 3/4 or last 1/4, 1/2, 3/4 portion) or frequency domain (with low- or high-pass filters at frequencies 100, 250, 500 and 1000 Hz), or by reversal of natural bellows. The playback experiments revealed that relatively large modifications in bellow temporal or frequency structure failed to impair Chinese alligators' bellowing behavior; even reversed bellows effectively evoked a positive response. In general, the first half of the bellow in temporal domain and frequencies below 500 Hz were critical for behavioral induction, while the last half of the bellow in temporal domain and frequencies above 500 Hz failed to produce a single positive response, implying a potential functional signal redundancy. The observed high tolerance to bellow variations in Chinese alligators may be an evolutionary adaptation to (1) the acoustic constraints of propagation imposed by dense vegetative habitats; or (2) a lack of selection pressure due to the low risk of incorrect conspecific recognition and heterospecific mating.