Characterizing the importance of habitat patches and corridors in maintaining the landscape connectivity of a Pholidoptera transsylvanica (Orthoptera) metapopulation

Since the fragmentation of natural habitats is one of the most serious problems for many endangered species, it is highly interesting to study the properties of fragmented landscapes. As a basic property, landscape connectivity and its effects on various ecological processes are frequently in focus. First, we discuss the relevance of some graph properties in quantifying connectivity. Then, we propose a method how to quantify the relative importance of habitat patches and corridors in maintaining landscape connectivity. Our combined index explicitly considers pure topological properties and topographical measures, like the quality of both patches (local population size) and corridors (permeability). Finally, for illustration, we analyze the landscape graph of the endangered, brachypterous bush-cricket Pholidoptera transsylvanica. The landscape contains 11 patches and 13 corridors and is situated on the Aggtelek Karst, NE-Hungary. We characterize the importance of each node and link of the graph by local and global network indices. We show how different measures of connectivity may suggest different conservation preferences. We conclude, accordingly to our present index, by identifying one specific habitat patch and one specific corridor being in the most critical positions in maintaining connectivity.This revised version was published online in May 2005 with corrections to the Cover Date.     

Occurrence pattern of Pararge aegeria (Lepidoptera: Nymphalidae) with respect to local habitat suitability, climate and landscape structure

Distribution patterns of wild species are affected by environmental variables, such as climate, anthropogenic land use or habitat quality, which act simultaneously at different scales. To examine the relative importance of particular factors and scales on population response we investigated the speckled wood butterfly Pararge aegeria (L.) as a model organism occupying semi-natural habitats. Its distribution was recorded in 23 study sites (5×5 km) over a 2 year study period. The sites were located in agricultural landscapes within seven Temperate European countries. Environmental predictors were mapped at a local and a regional scale. Logistic regression models were then developed to represent humid (beneficial) and dry (adverse) weather conditions during larval development. The humid year model predicted that P. aegeria is equally but generally not very dependent on local and regional factors, resulting in generally high occurrence probabilities. In contrast, the dry year model predicted severe restrictions of P. aegeria to both high quality patches and landscapes with beneficial structural and climatic preconditions. As both models resulted in entirely different predictions, our study showed that the sensitivity of P. aegeria to local and landscape features might change, and that factors of less importance could easily become limiting factors. The results stress that high quality landscape is important at both the local and regional scale even for species that are considered relatively robust. They also sound a note of caution when predictions about population response for management purposes are based on just a single or a few year(s) of observation.     

不同水生蔬菜对斜纹夜蛾药剂敏感性的影响

采用浸叶法测定了取食不同水生蔬菜的斜纹夜蛾对5种药剂的敏感性,对取食不同水生蔬菜的斜纹夜蛾幼虫进行了解毒酶活性测定.结果表明:取食莲藕、芋、水芹、人工饲料的斜纹夜蛾幼虫对氟啶脲(chlorfluazuron)、毒死蜱(chlorpyrifos)、茚虫威(indoxacarb)、溴虫腈(chlorfenapyr)和甲维盐...     

Comparison and development of new graph-based landscape connectivity indices: towards the priorization of habitat patches and corridors for conservation

The loss of connectivity of natural areas is a major threat for wildlife dispersal and survival and for the conservation of biodiversity in general. Thus, there is an increasing interest in considering connectivity in landscape planning and habitat conservation. In this context, graph structures have been shown to be a powerful and effective way of both representing the landscape pattern as a network and performing complex analysis regarding landscape connectivity. Many indices have been used for connectivity analyses so far but comparatively very little efforts have been made to understand their behaviour and sensitivity to spatial changes, which seriously undermines their adequate interpretation and usefulness. We systematically compare a set of ten graph-based connectivity indices, evaluating their reaction to different types of change that can occur in the landscape (habitat patches loss, corridors loss, etc.) and their effectiveness for identifying which landscape elements are more critical for habitat conservation. Many of the available indices were found to present serious limitations that make them inadequate as a basis for conservation planning. We present a new index (IIC) that achieves all the properties of an ideal index according to our analysis. We suggest that the connectivity problem should be considered within the wider concept of habitat availability, which considers a habitat patch itself as a space where connectivity exists, integrating habitat amount and connectivity between habitat patches in a single measure.     

粗胫翠尺蛾对不同荔枝品种的选择性研究

通过田间调查、电生理和行为学测定,研究了粗胫翠尺蛾(Thalassodes immissaria Walker)对5个荔枝品种(‘糯米糍’、‘妃子笑’、‘桂味’、‘黑叶’、‘淮枝’)的选择性。连续3 a田间调查显示,‘糯米糍’和‘妃子笑’受害较重,100梢虫数量平均为66.87头和58.70头,而‘淮枝’受害较轻,100梢虫数量平均为29.80头。粗胫翠尺蛾对‘桂味’、‘糯米糍’和‘妃子笑’3个品种叶片气味的相对触角电位值高于‘黑叶’,而对‘淮枝’的反应值最低。在Y型嗅觉仪测试中,粗胫翠尺蛾成虫更趋向于‘糯米糍’和‘妃子笑’,而对‘淮枝’的趋向性最差,‘糯米糍’和‘妃子笑’相比差异不显著。这些试验结果共同证明了粗胫翠尺蛾对5个荔枝品种具有选择性,而荔枝叶片气味在粗胫翠尺蛾寄主选择时具有重要的行为导向作用。     

荔枝蒂蛀虫的产卵选择性研究

【目的】荔枝蒂蛀虫是荔枝、龙眼上的主要害虫,深入认识其产卵选择机制,对于该虫的有效控制有重要意义。【方法】通过产卵选择试验,测定荔枝蒂蛀虫对荔枝果实、产卵介质表面纹理结构、颜色、形状和大小以及荔枝嫩叶和老叶等的产卵选择。【结果】荔枝果实可吸引荔枝蒂蛀虫产卵,即使在无法接触果实的情况下,成虫也可在产卵介质上产卵,其落卵量与直接产于果实上的落卵量无显著差异。但将荔枝果实密封包裹或烘制成果干后,则未观察到成虫在上面产卵。可见,荔枝果实吸引荔枝蒂蛀虫产卵的活性物质主要存在于其气味中。荔枝蒂蛀虫对产卵介质的表面纹理结构有选择性,成虫在200~400目(0.038~0.075 mm)筛网表面产卵较多,在复印纸、80目(0.18 mm)和100目(0.15mm)筛网表面产卵较少,该虫偏好在表面具有细小缝隙的产卵介质上产卵,表面过于光滑或缝隙过大均会减少其落卵量。但当荔枝果实被密封包裹后,即使表面纹理结构适合,成虫也不产卵。荔枝蒂蛀虫对产卵介质颜色、形状和大小均无显著的选择性。此外,荔枝蒂蛀虫可在装有荔枝嫩叶和老叶的产卵介质上产卵,其落卵量与装有荔枝果实的产卵介质上的落卵量无显著差异,说明荔枝叶片和果实一样,均可吸引成虫产卵。【结论】荔枝果实、嫩叶和老叶均可吸引荔枝蒂蛀虫产卵,该虫对产卵介质表面纹理结构有选择性。荔枝叶片表面光滑,可能是荔枝蒂蛀虫在自然条件下较少选择在叶片上产卵的重要原因。     

毛健夜蛾对不同寄主和寄主不同部位的取食选择性

以葱连和菠菜为寄主材料,研究了毛健夜蛾幼虫对不同寄主和寄主不同部位的取食选择性,及对受害及未受虫害叶的选择性和对葱莲不同部位的选择性。以期为有效防治该害虫提供技术参考。结果表明:试验进行至0.5、1.0、1.5和2.0h时,取食葱莲的幼虫数显著高于取食菠菜的;试验进行至0.5、1.0、1.5和2.0h时,取食虫害叶的幼虫数高于取食未受害叶的,但二者无显著性差异;幼虫对葱莲不同部位的取食选择性由高到低依次为花、花茎、叶和球茎,表明毛健夜蛾幼虫主要喜食寄主葱莲的较嫩器官(花、花茎、叶)。     

Bird populations in native forest patches in south-eastern Australia: the roles of patch width,matrix type (age) and matrix use

We surveyed birds in patches of native eucalypt forest and in surrounding exotic matrix (Radiata pine forests) in south-eastern Australia. Our objectives were: (1) to examine the influence of the width of native forest patches and the age of surrounding pine forests on bird occurrence in patches of native forest; and (2) to verify the relationship between the use of the surrounding pine matrix and bird species response to variation in width of patches of native forests. A total of 32 study sites (boundaries between eucalypt and pine forests) were surveyed. Birds were counted by the area search method within 0.5-ha quadrats. Data were analysed using generalised linear models. Wide patches of eucalypt forest supported higher species richness and greater numbers of birds, such as foliage searchers and nectarivores, than narrow patches. Matrix age also influenced the occurrence of some species in native patches. The abundance of species in wide and narrow patches of native forest was related to their use of the matrix. This was true for native forests surrounded by old but not by young pine forests. We suggest that management in wood production landscapes take into account both characteristics of native patches and the surrounding matrix. Negative impacts of fragmentation in managed landscapes might be reduced by promoting matrix types that are suitable for bird species.     

Resistance of 57 greenhouse-grown accessions of Lycopersicon esculentum and three cultivars to Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae)

The aim of this study was to evaluate resistance to Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) by antixenosis on 57 Lycopersicon esculentum Mill. accessions from the Horticultural Germplasm Bank (HGB) of Universidade Federal de Viçosa and by the three commercial cultivars (Santa Clara, Moneymaker and TOM-601) under greenhouse conditions. A randomized complete block design was used with three replications. Infestations with T. absoluta adults were performed weekly and the following characteristics were evaluated: number of small, large and total mines/leaf and % of leaves mined at days 60, 75 and 90 after planting. Low infestation occurred at days 60 and 75 but at day 90, infestation was sufficient to evaluate insect damage. Based on these data it was concluded that only accessions HGB-674 and HGB-1497 appeared to be the most promising. In addition, to determine possible chemical causes of resistance, hexane extracts were analyzed at day 90 by gas chromatography/mass spectrometry and the major peaks identified by a mass spectral database using similarity index. Nine hydrocarbons, viz., hexadecane, heptadecane, eicosane, tricosane, 2-methyltricosane, tetracosane, hexacosane, octacosane and triacontane were identified in the hexane extracts in many samples. Tricosane, tetracosane and hexacosane presented significant correlations with the leaves mined. Only tricosane presented a negative correlation with the number of small mines (r = −0.28), total number of mines (r = −0.27) and % of leaves mined (r = −0.22). However, tetracosane and hexacosane presented significant positive correlations (r = 0.25 and 0.24, respectively) with the % of leaves mined.     

Effects of patch attributes, barriers, and distance between patches on the distribution of a rock-dwelling rodent (Lagidium viscacia)

We tested whether size of habitat patches and distance between patches are sufficient to predict the distribution of the mountain vizcacha Lagidium viscacia a large, rock-dwelling rodent of the Patagonian steppe Argentina, or whether information on other patch and landscape characteristics also is required. A logistic regression model including the distance between rock crevices and depth of crevices, distance between a patch and the nearest occupied patch, and whether or not there was a river separating it from the nearest occupied patch was a better predictor of patch occupancy by mountain vizcachas than was a model based only on patch size and distance between patches. Our results indicate that a simple metapopulation analysis based on size of habitat patches and distance between patches may not provide an accurate representation of regional population dynamics if patches vary in habitat quality independently of patch size and features in the matrix alter connectivity. This revised version was published online in August 2006 with corrections to the Cover Date.     

Hydrological behaviour of rain gardens and plant suitability: A study in the Veneto plain (north-eastern Italy) conditions

Since spring 2011 the roof of a building on the Agripolis Campus of the University of Padova (Italy) has been used as a drainage area for two rain gardens with a circular area of about 10% and 20% of the drainage area respectively. To improve soil infiltration, the topsoil was removed up to the depth of 1 m and filled with a mix of 50% sand, 25% compost and 25% of the existing topsoil. Herbaceous perennials were selected and planted to test their adaptability to different soil water conditions in the rain garden. To evaluate the capacity of each rain garden to manage stormwater runoff a simplified water balance was done, estimating actual evapotranspiration using the WUCOLS method. From autumn 2012 runoff volumes were collected just from one pitch of the roof, and directed only into the smaller rain garden that became equal to 15% of the new roof drainage area. We thus had the possibility to test the functionality of rain gardens with three different percentages of roof drainage area: 10, 15 and 20%, even if in different periods. Results are presented relating to a four-year experimental period. Regarding hydrological behaviour, the input water volumes caused a slight overflow only during a few rainfall events. Consequently, the results showed a high capacity to manage stormwater runoff and also in the smaller rain garden almost the total roof runoff volumes infiltrated into the soil. As regards plants, the results indicated that the growth is affected by their position in the rain garden, from the wettest condition in the centre to the driest at the perimeter, except for Hemerocallis hybrida that showed great adaptability in all positions. Aster novi-belgii, Echinacea purpurea, Iris pseudacorus, Molinia caerulea and Rudbeckia fulgida also showed good adaptation, even if not in all rain garden zones, with highly aesthetic results. Lythrum salicaria and Saponaria officinalis plants appeared to be unsuitable for rain gardens. The results of the experiment have shown that, in the Veneto plain environment, rain gardens with a size of 10–15% of the roof drainage area can ensure both the sustainable management of stormwater runoff and a high aesthetic functionality.     

乙酸叶醇酯对梨小食心虫性信息素的增效作用

【目的】明确植物寄主挥发物对梨小食心虫性信息素的增效作用。【方法】将不同剂量的乙酸叶醇酯[(Z)-3-hexenyl acetate]制成增效诱芯或直接滴加到梨小食心虫性信息素诱芯,通过对比田间诱蛾量,比较不同处理诱芯的诱蛾效果和诱蛾动态。【结果】乙酸叶醇酯单独使用不能诱捕到梨小食心虫,直接滴加到性信息素诱芯也不能提高其诱蛾效果;30μg的乙酸叶醇酯制成的增效诱芯能显著提高性信息素对梨小食心虫的诱捕能力。【结论】乙酸叶醇酯可以作为性信息素增效剂,能显著的提高性信息素对梨小食心虫的诱捕效果和反映田间发生动态。     

Low seed/nut productivity in cashew (Anacardium occidentale): Effects of self-incompatibility and honey bee (Apis mellifera) foraging behaviour

Summary

The roles of self- versus cross-pollination and honey bee (Apis mellifera L.) foraging behaviour in low nut yield of cashew (Anacardium occidentale L.) were studied in NE Brazil in 1997 and 1998. It was shown that both self- and cross-pollination can set fruits in cashew, but most of fruits originating from self-pollination are shed 9–15 d after pollination, and fruits harvested are primarily from cross-pollination. Honey bees display foraging behaviour in cashew orchards conducive to cross-pollination, but in plantations originating from clonal material they failed to increase fruit yield despite cashew's dependence on insect pollination. It is concluded that cashew has a mechanism of selective abortion through which it discards self-pollinated fruits and that honey bees can contribute to increased fruit yield only when cashew trees of genetically diverse origin are found in the same orchard.     

Role of plant age in the resistance of Lycopersicon hirsutum f. glabratum to the tomato leafminer Tuta absoluta (Lepidoptera: Gelechiidae)

The objective of this work was to study the role of plant age in the resistance of tomato, Lycopersicon hirsutum, to the tomato leafminer Tuta absoluta (Meyrick). Determination of the levels of tridecan-2-one and undecan-2-one in L. hirsutum were made at three different ages (2–4 months after germination), as well as the leaf area, and the density and types of trichomes present on L. hirsutum and L. esculentum. This information gathered was correlated with the following biological characteristics of T. absoluta: rates of oviposition and egg eclosion; length of egg, larval and pupal stages; mortality in the larval and pupal stages; pupal weight and proportion of females. T. absoluta showed higher oviposition and egg eclosion, as well as lower mortalities and shorter larval and pupal periods in L. esculentum than in L. hirsutum. The proportion of females obtained was also higher on L. esculentum. The rate of egg eclosion and proportion of females as well as the length of the larval stage and the mortality of larvae appeared to be affected by plant age. A higher proportion of females, mortality of larvae and length of the larval period were obtained with older plants of L. hirsutum, while the rate of egg eclosion was higher for L. hirsutum plants that were 3 months old. For L. esculentum, plant ageing increased larval mortality. It seems that the glandular trichome density in L. hirsutum increased with plant age leading to an increase in the levels of tridecan-2-one, which slows larval development.     

Genetic diversity in mainland and island populations of the endangered Pancratium maritimum L. (Amaryllidaceae) in Tunisia

Tunisian Pancratium maritimum L. populations are at present endangered and represented by scattered individuals as a result of coastal habitat destruction caused by urbanization and overharvesting for its significant ornamental interest. Nineteen populations growing in mainland and island habitats were sampled for allozyme diversity to assess their genetic diversity and structuration using seven isozymes revealed by starch gel electrophoresis. The species exhibited relatively high levels of genetic diversity (the mean A_p = 1.37, P = 37.4%, and H_e = 0.100), indicates a preferentially outcrossing mating system.     

14种植物乙醇提取物对荔枝粗胫翠尺蛾成虫产卵和幼虫取食的影响

测定了14种植物乙醇提取物对荔枝粗胫翠尺蛾(Thalassodes immissaria Walker)成虫产卵、2龄幼虫取食及存活的影响.结果表明,非洲山毛豆、洋紫荆、肉桂、华南毛蕨和少花龙葵5种植物提取物对荔枝粗胫翠尺蛾的产卵抑制作用最佳,处理1 d后的产卵抑制率分别为87.50%、81.25%、78.73%、71...     

尖眼蕈蚊的生物学及综防研究

本文对苏州地区常见的一种尖眼蕈蚊的形态进行了详细的观察 ,对其为害、生物学和生态学等方面作了研究 ,讨论了该虫的发生原因 ,并针对其发生规律和结合本地区菇农的生产实践 ,提出了相应的综合防治措施。     

If a tree falls in the forest: terrestrial habitat loss predicts caddisfly (Insecta: Trichoptera) assemblages and functional feeding group biomass throughout rivers of the North-central United States

Landscape Ecology - Understanding the specific natural and anthropogenic drivers of aquatic insect assemblages and feeding ecology is critical to managing aquatic ecosystems. Utilizing the counts...