Persistence and stability of macroinvertebrate communities in streams of Denali National Park, Alaska: implications for biological monitoring

1. Macroinvertebrate communities were studied from 1994 to 2001/2002 (except 1997) in six streams in Denali National Park, interior Alaska. All six streams were potential reference streams with no known impairment. 2. Abundance of individual taxa varied markedly from year to year. Overall, abundance decreased over the study period, particularly with respect to mayflies. Stonefly taxa showed lower persistence and were sometimes absent from a stream in any particular year. 3. Mean community persistence for the six streams, as measured by Jaccard's similarity coefficients between years, varied from 0.48 in the year pair 1999–2000 to 0.78 in 1998–99. Tattler Creek (a small stable stream) supported the most persistent macroinvertebrate community and Highway Pass Creek (a small, unstable creek) the least. Mean community persistence showed a significant relationship with mean winter snowfall (November to March) for the six streams. 4. The highest community compositional stability was found in Tattler Creek and the lowest in Highway Pass Creek, but stability varied markedly over time for the six streams, peaking in 1994–95 and reaching a minimum in 2000–01. Compositional stability was significantly related to the Pfankuch Index of channel stability. 5. The composition metrics % Chironomidae, % dominant taxa, %EPT, % Ephemeroptera and % Plecoptera, employed as part of the Alaska Stream Condition Index, varied over almost their entire range in these pristine streams across the 9 years of the study. 6. This study demonstrates the wide range of natural variation that occurs in benthic macroinvertebrate communities in these pristine central Alaskan streams, potentially limiting the applicability of composition metrics for the biological monitoring of water quality in these systems.     

Comparative transmission of, and varietal reaction to, three isolates of rice tungro virus disease

Comparative transmission by leafhoppers of three tungro isolates obtained from the Philippines, India and Malaysia, and of an infectious clone of the Philippine isolate of rice tungro bacilliform virus (RTBV) by agroinoculation, was conducted on 12 rice cultivars. The symptoms, including height of inoculated plants were recorded and the efficiency of RTBV and rice tungro spherical virus (RTSV) transmission was determined by enzyme-linked immunosorbent assay. In most cases, the reduction of height and leaf symptoms of plants infected with RTBV and/or RTSV by the three isolates were similar in any given cultivar. On cultivar ASD 7 , the Malaysian isolate showed more severe yellow orange leaf discolouration symptoms than the Indian isolate which in turn had more severe leaf discolouration than the Philippine isolate. On the other hand, cultivars ASD 7 and Ptb 18 produced the most severe yellow orange leaf discolouration when agroinoculated with an infectious RTBV clone of the Philippine isolate. There was some variation in the transmission profile of the two tungro viruses among the three isolates. However, there was no one clear set of characteristics by which one could use cultivars to distinguish isolates. The amount of viral DNA in agroinfected plants of cultivars Utri merah, Balimau putih, Utri Rajapan and ARC 11554 was low, while the amount was high in cultivars TN1, ASD7, Ptb 18 and TKM 6. There was high correlation between the amount of viral coat protein by ELISA and viral nucleic acid by DNA hybridisation on 10 agroinoculated rice cultivars; this might indicate that similar proportions of the total RTBV DNA are encapsidated in each cultivar.     

The diversity of hemi-epiphytic figs (Ficus ; Moraceae) in a Bornean lowland rain forest

The diversity and niche specificity of hemi-epiphytic figs in a lowland dipterocarp forest in Sarawak were investigated in 1998. Twenty-seven fig species (264 individuals, c. 120 ha) colonized a diversity of host taxa (35 families), but densities were very low and only 1.77% of trees> 30 cm d.b.h. were occupied. There were no significant associations with host taxa or host-bark roughness but among 11 common species (≥9 individuals) the distributions of all other parameters (host-d.b.h., height and position of colonization, crown illumination, soil-texture and slope-angle) were significantly different, and we identified five fig guilds. The guilds corresponded to canopy strata, and appeared to reflect the establishment microsite requirements of different species. A fundamental trade-off within the hemi-epiphytic habit was revealed: Species colonizing larger hosts were rarer, because of lower host densities and more specific microsite requirements, but had better light environments and attained a larger maximum size. The single strangler species appeared to escape many of these constraints, and an important source of mortality caused by host-toppling, indicating the advantages of this strategy. Thus, the hemi-epiphytic figs in this community have come to fill a remarkable diversity of niches, despite low levels of competition, through the exigencies of a complex environment.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 78 , 439–455     

湖南参属的归并及亚洲楤木属(五加科)的一个新种和一些名称的变更

分子与形态证据表明湖南参 (HunaniopanaxhypoglaucusC .J.Qi&T .R .Cao)起源于木属 (AraliaL .) ,湖南参的近缘种为寄生五叶参 (Araliaparasitica)和轮伞五叶参 (Araliaverticillata) ,形态证据支持湖南参为轮伞五叶参的姐妹种 ,此 2种具轮伞花序这一共衍征。为了保证木属的单系性 ,现将湖南参并入木属 ,并作如下新组合 :Araliahypoglauca (C .J .Qi&T .R .Cao)J.Wen&Y .F .Deng .本文报道了湖南参在广西的新分布。目前的形态学和分子数据均不支持早先提出的湖南参与树参属 (Dendropanax)的近缘关系。本文亦报道了木属的 1新种、 2新种组合和 1个新名称 :AraliashangianaJ .Wen .sp .nov .(向氏五叶参 ,新种 ) ;Araliaglabrifoliolata (C .B .Shang)J .Wen .comb .nov . (光叶五叶参 ,新组合 ) ;Araliastellata (King)J.Wen ,comb .nov . (星毛羽叶参 ,新组合 )和AraliadelavayiJ .Wen .nom .nov .(云南五叶参 ,新名称 )。     

Some Microscopical Observations of Functioning Sieve Tubes of Heracleum using Nomarski Optics

The study of isolated phloem in Heracleum has been extendedto intact functioning sieve tubes. Techniques of phloem dissectioncombined with Nomarski interference optics have been developedto permit useful visual observations, photomicrography, andciné photographs of sieve tubes which are apparentlynormal. In these preparations, plastids and organelles calledby us ‘marker particles’ are visible in rapid bouncingmotion, and the state of dispersal of these particles is relatedto the amount of damage done to the preparations. The movement of the marker particles and their subsequent fixationshows that they are apparently attached to or restrained byan invisible network in situ. The network is very sensitiveto disturbance and readily collapses around the sieve platesto form slime plugs upon damage to the sieve element. The markerparticles do not move through the cell nor across sieve platesin mature Heracleum. In young cells cyclosis is observable alongthe periphery and this suggests that a vacuole may then be present.In undamaged mature cells there was evidence neither of a vacuolenor of trans-cellular tubules of any size optically detectable. The motion of the particles was greater than Brownian movementand appeared to be under some physiological control. Their movementprobably indicated the presence of an operating transport phenomenon,either because solution was moving past them in the sieve tubeor because they were themselves attached to a contractile networkactively in pulsatory motion. Nearby companion and parenchymacells showed normal cytoplasmic streaming. Proposed mechanisms of translocation involving cytoplasmic streamingdo not seem to be applicable to the phloem of Heracleum. Themovement of the marker particles seemed to agree best with amechanism of ‘activated’ mass flow.     

An improved technique for obtaining well-spread metaphases from plants with numerous large chromosomes

Preparations that contain well-spread metaphase chromosomes are critical for plant cytogenetic analyses including chromosome counts, banding procedures, in situ hybridization, karyotyping and construction of ideograms. Chromosome spreading is difficult for plants with large and numerous chromosomes. We report here a technique for obtaining cytoplasm-free, well-spread metaphases from two Amaryllidaceae species: Sprekelia formosissima (2n = 120) and Hymenocallis howardii (2n = 96). The technique has three main steps: 1) pretreatment to cause chromosome condensation, 2) dripping onto tilted slides coated with a thin layer of pure acetic acid and 3) application of steam and acetic acid to produce cytoplasmic hydrolysis, which spreads the chromosomes.     

Effect of climate change on mast-seeding species: frequency of mass flowering and escape from specialist insect seed predators

Global surface temperatures are expected to increase by several degrees in the next century, with potentially large but poorly understood impacts on ecological interactions. Here we propose potential effects of increased temperatures on ecologically dominant New Zealand grasses (Chionochloa spp.) that mass flower and mast seed. Twenty-two years’ data from five masting Chionochloa species in New Zealand showed that the cue for heavy flowering was unusually high temperature in the summer of the year before flowering. Attack by predispersal insect seed predators was much reduced in mast years, apparently because predator populations were satiated. Increased temperatures would greatly decrease interannual variation in Chionochloa flowering, allowing seed predator populations to increase and potentially to devastate the seed crop annually. Similar responses are likely in masting species worldwide. This previously unrecognized effect of global warming could have widespread impacts on temperate ecosystems.     

太湖生态系统能量闭合特征及其影响因素

地表能量不闭合不仅限制了涡度相关观测数据在陆面模型发展和验证等应用性研究中的价值,还给生态系统CO2源汇特征辨析带来不确定性。基于太湖避风港站2012年涡度相关通量、辐射、气象和水温梯度观测数据,分析了太湖能量闭合的多尺度(小时、日和月)时间变化特征,阐述了大气稳定度、摩擦风速和湖风对太湖能量闭合状况的影响。结果表明:太湖小时尺度的能量闭合度为0.59,且昼夜差异较小;日尺度的能量闭合度为0.73,在内陆水体观测结果中处于中等水平;月平均能量闭合度呈现冬季高、夏季低的季节变化特征;年平均时太湖仍有27%的能量不闭合。因摩擦风速减小,太湖能量闭合度在大气极不稳定条件下要比弱不稳定条件下结果低0.3;对于太湖这类大型浅水湖泊,其能量闭合度全天都受动力湍流交换强度制约,能量闭合度随摩擦风速增大而显著提高;虽然湖风发生使太湖小时尺度的能量闭合度降低了0.1,但其影响在日尺度上并不明显。     

First records of Leiodytes nicobaricus (Redtenbacher) and Platambus stygius (Régimbart) in Korea (Coleoptera: Dytiscidae)

Two dytiscid beetle species, Leiodytes nicobaricus (Redtenbacher) and Platambus stygius (Régimbart), are identified for the first time in Korea. Diagnoses, habitus and scanning electron microscopy photographs, and line drawings of the diagnostic characters are provided.     

Taxonomic notes on the genus Holepyris (Hymenoptera: Bethylidae) from Korea with descriptions of six new species

Six new species of the genus Holepyris (Hymenoptera: Bethylidae: Epyrinae) from Korea are described: H. brevicarinatus sp. nov., H. crinitus sp. nov., H. dimidiatus sp. nov., H. longicephalus sp. nov., H. mucro sp. nov. and H. multo sp. nov. They are described with illustrations of male genitalia and the biometric measurement data. A key to the Korean species of Holepyris based on males is provided.