2007－2012 年佛冈县稻飞虱灯下发生期及种群数量动态分析

明确佛冈县稻飞虱灯下发生期及灯诱种群数量动态,对当地稻飞虱的预测预报和防治工作具有重要意义.根据佛冈县2007-2012年白背飞虱和褐飞虱的灯诱数据,分析了该县白背飞虱和褐飞虱的灯下始见日、终见日、发生期及灯诱量等.结果表明在佛冈地区,白背飞虱和褐飞虱混合发生;白背飞虱的灯下始见日集中在3月底至4月上旬,明显比褐飞虱早一个月,终见日均在10月下旬,差别不大;稻飞虱在早稻和晚稻期间均会出现大小不一的灯诱高峰,早稻期间白背飞虱高峰期集中在5月中旬至6月中旬,褐飞虱灯诱高峰期较迟,主要在7月中旬前后;晚稻期间向背飞虱高峰期大多在9月上旬至10月上旬,褐飞虱高峰期在10月份;早稻期间,白背飞虱的灯诱量占绝对优势,晚稻期间褐飞虱的灯诱量上升,与白背飞虱灯诱量基本持平.因此,佛冈县稻飞虱的灯下发生期及种群数量动态在一定程度上可反映当地稻飞虱的发生情况.     

Micro-topography driven vegetation patterns in open mosaic landscapes

Elevation models based on remotely sensed data, especially high-resolution Digital Terrain Models (DTMs) generated using airborne laser scanner (ALS) data, are increasingly being used for the analysis of plant diversity patterns in open landscapes. The vegetation pattern of alkali landscapes shows a high correlation with the position of water table and salt accumulation, which are strongly correlated with topographic variations occurring at a small spatial scale of a few decimetres (micro-topography). In this study we classified eight grassland associations in an alkali landscape based on a DTM generated from ALS data at a pixel size of 0.25 m, and 30 variables derived from the DTM, using an ensemble learning method (Random Forest). Our aim was to identify the micro-topographic variables which could be indicators of vegetation pattern in alkali landscapes. The associations range from Cynodon pastures (short dry grasslands on soil with low salt content) occupying the highest elevations to Beckmannia meadows (wet grasslands on soils with moderate salt content composed of tall grass species) at the lowest elevations, with an elevation difference of approximately 1.2 m between the two. Apart from slope, aspect and curvature, we used Topographic Wetness Index (TWI), and Topographic Position Indices (TPI) at various kernel sizes ranging from 50 cm to 500 m for the classification. The eight associations were also grouped into four aggregated categories — loess grasslands, alkali steppes, open alkali swards and alkali meadows — for further analysis. Vegetation of the studied alkali landscape could be classified into the eight associations with an accuracy of κ: 0.56, and into the four aggregated categories with an accuracy of κ: 0.77 using all the variables. Sequential backward and forward selections of variables were implemented to reduce the number of variables while maximising the accuracies, resulting in increased accuracies of κ: 0.72 and κ: 0.83 for the associations and aggregated categories using six and three variables respectively. TPI at different kernel sizes, previously used to explain vegetation distribution in mountainous areas, was found to be a better indicator of vegetation types than absolute elevations in lowlands where the elevation differences are more subtle. Two characteristic features of the study area — erosional channels and alkali steps — could also be delineated using micro-topographic variables. The results point to the possibility of large-area mapping and monitoring of grasslands where micro-topography is an indicator of vegetation, using only the elevation data from ALS.     

Studies of Antarctic yeast for β-glucosidase production

Moss and lichen samples from the region of the Bulgarian base on Livingston Island, Antarctica were examined for the presence of yeasts. Six pure cultures were obtained. They were screened for -glucosidase production and two of them were selected. These were identified as Cryptococcus albidus AL₂ and C. albidus AL₃, according to their morphology, reproductive behaviour, and growth at different temperatures, salt concentrations, nutritional characteristics and various biochemical tests. These strains were examined for biosynthesis of -glucosidase on different carbon sources under aerobic conditions. High exocellular and endocellular activities were obtained when they were grown on cellobiose, methyl--D-glucopyranoside and salicin. The time course of growth and -glucosidase production of the yeast was examined by cultivation in a medium with cellobiose under aerobic conditions at temperatures 18 and 24 °C for 96 h. Cryptococcus albidus AL₂ and C. albidus AL₃ synthesized exocellular enzyme, respectively 58.33 and 55.83 U/ml and endocellular enzyme 137.75 and 205.34 U/ml at 24 °C for 72 h of the cultivation.     

不同水稻品种对白背飞虱取食和产卵选择性的影响

为进一步了解抗虫品种对白背飞虱的抗性机制,运用标准苗期群体鉴定法、蜜露测定法等方法,研究了8个不同抗性水平水稻品种对白背飞虱Sogatella furcifera(Horváth)取食和产卵选择性的影响。结果表明,水稻品种IR54751-2-34-10-6-2、MR1532、Rathu Heenati表现为高抗;IR54742-1-18-12-11-2、IR71604-4-1-4-10-8-5-3-1表现中抗;IR72表现为中感;BG367-7、TN1表现为高感。白背飞虱对MR1532、IR54751-2-34-10-6-2和Rathu Heenati上的取食趋性较弱,这几个品种对白背飞虱取食量的影响最大;MR1532、Rathu Heenati和IR54751-2-34-10-6-2上的卵量显著少于产在对照品种TNI的卵量,IR54742-1-18-12-11-2、IR71604-4-1-4-10-8-5-3-1、IR72上的卵量与产在对照品种TNI上的卵量差异不显著。白背飞虱在抗虫品种上并非完全不取食,只是抗性越强取食量越少;抗性表现为抗的品种对白背飞虱成虫产卵选择性有明显影响。     

Life history predicts advancement of avian spring migration in response to climate change

An increasing number of studies demonstrate that plant and animal phenologies such as the timing of bird migration have been advancing over the globe, likely as a result of climate change. Even closely related species differ in their phenological responses, and the sources of this variation are poorly established. We used a large, standardized dataset of first arrival dates (FAD) of migratory birds to test the effects of phylogenetic relationships and various life-history and ecological traits on the degree to which different species adapt to climate change by earlier migration in spring. Using the phylogenetic comparative method, we found that the advancement of FAD was greater in species with more generalized diet, shorter migration distance, more broods per year, and less extensive prebreeding molt. In turn, we found little evidence that FAD trends were influenced by competition for mating (polygamy or extra-pair paternity) and breeding opportunities (cavity nests). Our findings were robust to several potentially confounding effects. These evolutionary correlations, coupled with the low levels of phylogenetic dependence we found, indicate that avian migration phenology adapts to climate change as a species-specific response. Our results suggest that the degree of this response is fundamentally shaped by constraints and selection pressures of the species' life history, and less so by the intensity of sexual selection.     

The importance of historical ecology for interpreting evolutionary processes in plants of oceanic islands

Oceanic islands and archipelagos are natural laboratories for investigating patterns and processes of evolution. Islands change with the course of time, resulting in a dynamic ontogeny over millions of years. The combined forces of tectonic plate subsidence and erosion from waves, wind, and rainwater bring about substantial geomorphological change over millions of years, until islands eventually disappear under the sea. Added to these long‐term natural changes to the environment of the islands are the changes caused by human activities in recent centuries. After humans reach a previously unpopulated island, they utilize the natural resources for their own survival, cutting forests for making houses, boats, and firewood. The size of the human population and the length of time on the island determine the degree of environmental impact. Evolutionary processes in plants of oceanic islands take place during ontogeny of the islands, resulting in population divergence, speciation, and hybridization. Due to the dramatic alterations suffered by many islands over millions of years, the present patterns of distribution and ecology of species within endemic groups may have little to do with the patterns when the species originated. Understanding these environmental changes is fundamental to infer a founder effect, reasons for levels of genetic variation within and among populations, and modes of speciation. Special caution must be exercised while making comparisons between groups located on islands of different geological ages and that have endured differing environmental modifications from humans. Examples are provided from the Juan Fernández Archipelago and Lord Howe Island.