Colonisation of pitcher plant leaves at several spatial scales

Abstract.  1. The effect of meso-scale (zone within bog and local plant density) and fine-scale (leaf length and resource availability) factors on the colonisation of pitcher plant leaves by arthropods was examined in an eastern Canadian bog.
2. In spring, the abundances of three arthropods, the mosquito Wyeomyia smithii , the midge Metriocnemus knabi , and the mite Sarraceniopus gibsoni , were determined for plots with low, moderate, and high densities of pitcher plants. All overwintering inhabitants were then removed from the plots. Newly opening leaves were colonised from outside the plots, and arthropod abundances were assessed again in autumn.
3. Pitcher plant fauna varied in their response to the meso-scale factors. In autumn (soon after colonisation), midges were more abundant in areas with high densities of pitcher plants. The relationship between mosquito abundance and plant density, and the variation in abundance among zones within the bog in the spring, were probably due to overwintering mortality.
4. All taxa responded to the fine-scale factors, leaf length, and capture rate, in the autumn, but the strength of the responses frequently depended on a meso-scale factor (plant density), in which responses were usually strongest where plants were sparse. Thus, the interaction between meso- and fine-scale processes needs to be considered when interpreting patterns of species abundance within arthropod assemblages in pitcher plant leaves.     

Age composition of masu salmon smolts in northern Japan

Smolts of anadromous masu salmon Oncorhynchus masou aged 3+ years were found in a northern Japanese river. This is the first recording of 3+ year smolts in Japan. These fish appeared to originate in the cold upper river where 2+ year parr were found during autumn.     

毛百合的组织培养和快速繁殖

以毛百合鳞片切块为外植体,置入不同激素配比的培养基中,观察和比较切块的近轴面、远轴面、侧面分化小鳞茎、芽和根的情况,并通过不同土质、不同温度移栽实验,选出试管苗移栽成活的最好方法。     

区域尺度的昆虫迁飞行为与害虫间歇性猖獗

60年代以来,随着耕作制度和栽培品种的改变以及高投入丰产措施的普遍推广,我国迁飞性害虫的发生范围不断扩大,猖獗频率逐渐增加,对农业生产的威胁日益严重[1～4]。国内曾多次组织全国性大协作,研究迁飞性害虫的迁飞规律、地方发生规律和测报防治技术,虽然取得了相当的成就,但仍满足不了生产上的要求。目前尚无法以足够的精度预报迁飞性害虫的迁入期、迁入区和迁入量,对灾变的预警能力一直在低水平徘徊。其中一个主要原因就是对迁飞性害虫的消长规律尚缺乏深层次的基础研究,尤其是宏观尺度的机制研究一直相当薄弱,而这恰恰是亟待早日解决的关…     

Complex role of predators in structuring soft-sediment macrobenthic communities: Implications of changes in spatial scale for experimental studies

In estuarine and coastal soft-sediment systems, the role that predators play in structuring communities appears to be variable. Attributes of a particular predator that influence its role in structuring the community include: the rate of prey consumption; the behaviour, morphology and mobility of the predator; and, in soft- sediment communities, sediment disturbances associated with feeding. Reviews of field experiments designed to assess the role of predators in influencing the structure and function of soft-sediment communities have concluded that many of the predators are generalists and there is usually a lack of competitive exclusion. Thus predation structures communities by many complex and indirect interactions that are often difficult to predict and generalize. Variations in the apparent strength and role of predation in structuring benthic communities may depend on a variety of ecosystem characteristics and/or aspects of study design. In this paper, I consider whether we have been conducting our experiments at the appropriate scales. Five case studies from Manukau Harbour (New Zealand) illustrate how small changes in the spatial scale can affect results, due to predator perceptions and prey mobility. The results of these studies demonstrate the need to identify scales at which predator effects are likely to be important and to fit experiments within the dynamics and heterogeneity of the system being studied. To do this, we need basic information on the natural history, behaviour and spatial and temporal variability of both predators and prey communities. We also need to be specific about scales of measurement when matching theoretical predictions to field observations/experiments. Finally, to enhance our ability to generalize from specific studies, we need to gather data that will enable us to both predict and test the importance of predation over a range of spatial and temporal scales.     

The effect of spatial scale on evenness

Abstract. The effect of spatial scale on species evenness has not previously been investigated. As the area of each sample of vegetation (i.e. the spatial grain) increases, evenness could in theory increase, decrease, or stay the same, though the simplest model predicts an increase. We use biomass data from four dune slack sites and two semi-arid grasslands, sampled to allow calculation of evenness at a range of spatial grains. In all six sites, evenness decreases as grain size increases, almost monotonically. It is hypothesized that such a pattern is a result of a general feature of plant species abundance distributions and of vegetation response to environmental microheterogeneity.     

The influence of spatial scale on cross-taxon congruence patterns and prediction accuracy of species richness

A comparison of species richness patterns of butterflies and birds was made using data from two grids of squares (small squares 137.5 km on a side and large squares 275 km on a side) covering western North America. Using geostatistical procedures, we found that the spatial patterns of species richness of these two taxa were related. The influence of grain size on the strength of this relationship was investigated by analysing the two data sets. For both data sets, the number of butterfly species in a square was a statistically significant predictor of the corresponding number of bird species. However, cross-validation techniques showed that the marginal improvement in prediction accuracy due to including butterflies as a predictor was greater in the large-square data. We explored the effect of areal extent on cross-taxon congruencies by investigating species richness patterns in four subsets of the small-square data. In regions with smaller areal extent, the cross-taxon congruence patterns were not substantially different from the pattern found in the full data set. Finally, using data-splitting techniques, we explored the relationships between prediction accuracy of species richness, sample size, areal extent of the sample, and grain size.     

Yeast metabolic innovations emerged via expanded metabolic network and gene positive selection

Yeasts are known to have versatile metabolic traits, while how these metabolic traits have evolved has not been elucidated systematically. We performed integrative evolution analysis to investigate how genomic evolution determines trait generation by reconstructing genome‐scale metabolic models (GEMs) for 332 yeasts. These GEMs could comprehensively characterize trait diversity and predict enzyme functionality, thereby signifying that sequence‐level evolution has shaped reaction networks towards new metabolic functions. Strikingly, using GEMs, we can mechanistically map different evolutionary events, e.g. horizontal gene transfer and gene duplication, onto relevant subpathways to explain metabolic plasticity. This demonstrates that gene family expansion and enzyme promiscuity are prominent mechanisms for metabolic trait gains, while GEM simulations reveal that additional factors, such as gene loss from distant pathways, contribute to trait losses. Furthermore, our analysis could pinpoint to specific genes and pathways that have been under positive selection and relevant for the formulation of complex metabolic traits, i.e. thermotolerance and the Crabtree effect. Our findings illustrate how multidimensional evolution in both metabolic network structure and individual enzymes drives phenotypic variations.