苜蓿切叶蜂授粉扩散行为及苜蓿种子增产效应的研究

对苜蓿切叶蜂(Megachilerotundata)为苜蓿授粉的田间群体扩散行为和苜蓿种子增产效应研究表明,以授粉后苜蓿种子增产效应为指标,发现苜蓿切叶蜂以蜂箱为中心向四周扩散,随着距离增大,蜂的扩散及授粉效应逐渐降低。但不同方向其扩散及授粉效应不同,以苜蓿种子产量Y≥50g·m^-2为高效区,50g·m^-2>Y≥30g·m^-2为中效区,30g·m^-2>Y≥15g·m^-2为低效区。在高效区和中效区内,东北方向扩散距离最远,分别为50和60m,其次是东和北;在低效区,向北扩散距离最远,可达100m,其次是东北和西北;西、南、西南和东南扩散距离较短。据此做出了高效区、中效区和低效区的苜蓿切叶蜂授粉扩散行为图,由此可直观地看到3个区的范围.     

苜蓿切叶蜂在我国的研究与应用现状

应用苜蓿切叶蜂MegachilerotundataFubricius为苜蓿授粉是苜蓿 (MedicagoL .)种植中不可缺少的措施之一 ,该文对苜蓿切叶蜂的生物学及羽化与环境因子的关系进行了阐述 ,指出影响苜蓿切叶蜂授粉及滞育的环境因子 ,分析了苜蓿切叶蜂繁育过程中病害及天敌的情况 ,介绍了繁育过程中的设备和管理技术。     

紫花苜蓿的传粉昆虫种类及其访花行为

紫花苜蓿(Medicago sativa)属典型的异花授粉植物,其种子生产主要依靠蜜蜂等传粉昆虫.本文对河西地区张掖实验站紫花苜蓿传粉昆虫种类及其访花行为进行了调查.结果表明:苜蓿访花昆虫共计22种,分别属于4个目,11个科,根据弹花效率初步确定鳞地蜂、黑颚条蜂、净切叶蜂、细切叶蜂和紫木蜂为河西地区主要传粉昆虫;主要传粉昆虫的日活动规律出现单峰型和双峰型2种,净切叶蜂、细切叶蜂和紫木蜂属于前者,只在11:30-15:30出现一个活动高峰,而鳞地蜂与黑颚条蜂则为双峰型,在9:30-11:30和16:30-18:30分别出现访花高峰,不同的传粉昆虫之间存在互补关系;主要传粉昆虫的弹花频率和小花停留时间存在显著差异,且访花行为与野生蜂体型紧密相关.     

海切叶蜂的筑巢和访花行为

【目的】研究毛乌素沙地重要野生传粉昆虫海切叶蜂Megachile maritima的筑巢和访花行为对保护其栖息环境具有重要意义。【方法】采用目测及拍照等方法对海切叶蜂的整个筑巢过程进行了连续观测;以2 m×2 m 样方的方式观测海切叶蜂的访花频率、单花停留时间及日活动规律等访花行为,其中日活动规律每天连续观测,共观测7天。【结果】海切叶蜂在沙土中筑巢,每巢只有一个巢室,其筑巢过程为：寻找合适的筑巢地点,挖巢,构建巢室,采集蜂粮,产卵,封住巢室,筑完一个巢。它连续筑完一个巢大约需要9 h。海切叶蜂构建一个巢室需要切取26～29片叶子,为每巢室采集蜂粮11～12次,每巢室内产卵1粒;在塔落岩黄芪和细叶益母草上的平均访花频率分别为（13.23±6.49）朵/min和（16.72±4.84）朵/min,平均单花停留时间分别为（3.08±2.48）s和（2.49±1.31）s。晴天,海切叶蜂在12:00～14:00期间活动较活跃。【结论】海切叶蜂不同个体之间的筑巢行为相似。该蜂在塔落岩黄芪和细叶益母草上的访花过程、访花频率及单花停留时间具有显著的差异。     

采用竹管蜂巢繁育苜蓿切叶蜂

对5种繁育苜蓿切叶蜂的蜂巢材料进行了筛选测定,结果表明,竹管的繁蜂效果较好,子代蜂的雌雄性比为1：1,而且竹管内的蜂茧均未被寄生蜂寄生。     

毛乌素沙地固沙植物披针叶黄华主要传粉昆虫及其访花行为

披针叶黄华(Thermopsis lanceolata)是我国西部地区早春重要野生蜜源植物,也是一种重要的固沙植物,然而对其繁殖特性的研究甚少.本文在系统调查披针叶黄华的访花昆虫基础上,确定其主要传粉昆虫种类、访花行为、传粉过程以及日活动规律,以期揭示主要访花者行为对其有性繁殖的影响.作者在内蒙古毛乌素沙地设置1个10m×10 m的样方,于2010和2011年在披针叶黄华盛花期,采用目测、拍照和摄像等方式对传粉昆虫进行观测,记录样方内主要访花昆虫种类、数量、访花行为及日活动规律.研究表明,大和切叶蜂(Megachile japonica)和戎拟孔蜂(Hoplitis princeps)是披针叶黄华的主要传粉者,但两种昆虫的访花频率存在显著差异;晴天时,大和切叶蜂在19:00-13:00和16:00-18:00出现两个活动高峰,而戎拟孔蜂只在11:30-16:30出现1个活动高峰,两种蜂的访花活动高峰期存在互补关系.大和切叶蜂访花同时具有盗蜜行为,但其盗蜜行为对披针叶黄华的结籽率没有显著影响.根据种群数量、访花频率综合判断,大和切叶蜂是披针叶黄华优势传粉蜂.     

科尔沁沙地紫花苜蓿的光合日动态

利用Li-6400光合测定系统,田间实地测定了紫花苜蓿3个品种（敖汉苜蓿、Rangelander和 阿尔冈金）的光合作用日变化特征.结果表明:不同生长年限紫花苜蓿3个品种的净光合速率(P_n)、蒸腾速率(T_r)和水分利用效率(WUE)日变化并不完全呈双峰曲线.其中,敖汉苜蓿和阿尔冈金叶片的P_n和T_r峰值均出现在9:00—11:00,Rangelander在11:00,最低值均出现在7:00和19:00;Rangelander和阿尔冈金叶片的WUE最高值出现在7:00,敖汉苜蓿在9:00,最低值均出现在15:00—17:00.综合分析P_n、T_r和WUE 3项指标,2 年生苜蓿各项指标最佳,1年生次之,而4年生最差;对P_n和T_r影响最大的环境因子是气温,其次是水分亏缺和空气相对湿度.     

双斑切叶蜂的筑巢习性

【目的】明确双斑切叶蜂Megachile leachella在沙地上的筑巢环境及筑巢特点,旨在当地利用人工巢管诱引其筑巢。【方法】采用目测和拍照等方法对双斑切叶蜂的整个筑巢过程进行了连续观察; 采用挖掘、测量方法对双斑切叶蜂巢内结构进行了观测;在室内对蜂茧在土中和指形管中的羽化情况进行了初步观测。【结果】双斑切叶蜂一般在废弃的泥墙或者沙地上蚂蚁等废弃的巢穴中筑巢,有时候它也在沙地上挖掘新巢筑巢。双斑切叶蜂用叶片构建巢室,一巢多室,各巢室首尾相接排列在巢中,筑完巢后用叶片将巢口封住。双斑切叶蜂构建一个巢室需要切取11～14片叶子,为每巢室采集蜂粮6～9次,每巢室内产卵1粒;在内蒙古毛乌素沙地,该蜂一年2代,第1代在6月中下旬羽化,第2代大约在7月下旬至8月上旬羽化,主要寄生性天敌有尖腹蜂Coelioxy sp.、青蜂Chrysis sp.。双斑切叶蜂能在指形管中羽化。【结论】双斑切叶蜂不同个体之间的筑巢行为相似,雌蜂可以用人工巢管进行诱集和驯化。     

简讯

<正> 加拿大K. W. Richards博士访华 应中国农业部的邀请,加拿大农业部昆虫学家、作物传粉专家K. w. Richards博士于1988年9月21日至10月16日到我国北京、黑龙江、河北和甘肃等地的苜蓿种植区进行了考察,对“中国引进和利用苜蓿切叶蜂Megachile rostundata为苜蓿传粉以提高苜蓿种子的产量和质量”的研究做了可行性调查。在北京农业大学就“苜蓿切叶蜂的生物学、生态学和管理”及“加拿大苜蓿种植管理与切叶蜂释放相协调”等内容做了学术报告,     

苹果传粉昆虫种类及其访花习性的研究

为了解苹果花期的传粉昆虫,更好地利用昆虫为苹果授粉,本文对山西运城临猗、临汾隰县苹果的传粉昆虫进行调查,结果表明:调查区苹果传粉昆虫共计23种,隶属于4目、14科,主要传粉昆虫依次为膜翅目的蜜蜂科、条蜂科、切叶蜂科、地蜂科和双翅目的食蚜蝇科。其中,意大利蜜蜂和毛附黑条蜂为主要传粉昆虫。日活动规律观察表明,蜜蜂属于双峰型,条蜂属于单峰型;条蜂出巢温度(温度为16.4℃)低于蜜蜂的出巢温度(18.8℃),11∶00-12∶00和15∶00-16∶00为蜜蜂访花高峰,条蜂访花高峰在10∶00-11∶00。     

Chalkbrood transmission in the alfalfa leafcutting bee: the impact of disinfecting bee cocoons in loose cell management systems

Understanding pathogen transmission could illuminate new methods for disease prevention. A case in point is chalkbrood in the alfalfa leafcutting bee [Megachile rotundata (F.)]. Propagation of this solitary bee is severely hampered by chalkbrood, a larval disease caused by Ascosphaera aggregata (Ascomycota). Alfalfa leafcutting bees nest in existing cavities in wood or hollow reeds and overwinter as larvae. In the early summer, emerging adults frequently must chew through dead, diseased siblings that block their exit, becoming contaminated with chalkbrood spores in the process. When alfalfa leafcutting bees are used as a commercial pollinator, the cocoons are removed from nesting boards to reduce chalkbrood transmission, but the disease is still common. To determine if these removed cocoons (called loose cells) are an important source of disease transmission, they were disinfected with a fungicide before bees were incubated, and released in the field. Chalkbrood prevalence among the progeny of the treated bees was reduced up to 50% in one field trial, but not significantly when tested in an on-farm trial. Thus, substantial disease transmission still occurred when the loose cells were disinfected, and even when clean nesting materials were used. In conclusion, pathogen transmission must still be occurring from another source that has yet to be identified. Another possible source of transmission could arise from bees that emerge midsummer in populations with a high percent of multivoltinism, but dirty nesting boards and feral bees also may be minor sources of transmission.     

Emergence success and sex ratio of commercial alfalfa leafcutting bees from the United States and Canada

Samples of overwintering alfalfa leafcutting bee, Megachile rotundata (F.) (Hymenoptera: Megachilidae), cells were sent to the laboratory as loose cells or in nesting boards from bee managers in the United States and in Canada. X-radiographs of cells were used for determining cell contents. Cells containing live prepupae were incubated, and the sex of emerging adults was recorded daily. Cells from which no adult emerged were dissected to determine the developmental stage of dead bees and sex of dead pupae or adults. Bee cells incubated in commercial settings and placed in alfalfa fields by the same bee managers described above also were evaluated to determine adult emergence success. The proportion of live bees in wood nesting boards from the United States was much lower than the live proportion in polystyrene nesting boards from Canada and loose cells overwintered in the United States. For laboratory-incubated loose cells, survival and sex ratios of bees from Canadian sources were statistically higher than those of U.S. bees, but the onset and duration of emergence times were similar. Fewer bees survived in the commercial setting than in the laboratory. Prepupal mortality was significantly higher than pupal or adult mortality, but there was no significant difference between the sexes in the likelihood of survival during incubation. This study supports the commonly held belief that alfalfa leafcutting bees raised in Canada and then sold to the United States represent a more viable source of bees than most bees produced in the United States.     

Risk of alfalfa transgene dissemination and scale-dependent effects

Pollen can function as a vehicle to disseminate introduced, genetically engineered genes throughout a plant population or into a related species. The measurement of the risk of inadvertent dispersal of transgenes must include the assessment of accidental dispersion of pollen. Factors to be considered include the rate of pollen spread, the maximal dispersion distance of pollen, and the spatial dynamics of pollen movement within seed production fields; none of which are known for alfalfa (Medicago sativa L.), an insect-pollinated crop species. Using a rare, naturally occurring molecular marker, alfalfa pollen movement was tracked from seed and hay production fields. Results indicated that leafcutter bees (Megachile spp.) used in commercial seed production show a directional, non-random bias when pollinating within fields, primarily resulting in the movement of pollen directly towards and away from the bee domicile. Within-field pollen movement was detected only over distances of 4 m or less. Dispersal of pollen from alfalfa hay and seed production fields occurs at distances up to 1000 m. By examining widely dispersed, individual escaped alfalfa plants and their progeny using RAPD markers, gene movement among escaped alfalfa plants has been confirmed for distances up to 230 m. The outcrossing frequency for large fields was nearly 10-times greater than that of research-sized plots. A minimum isolation distance of 1557 m may be required to prevent gene flow in alfalfa. Data suggest that complete containment of transgenes within alfalfa seed or hay production fields would be highly unlikely using current production practices. Received: 20 March 1999 / Accepted: 11 November 1999     

Fungicide tests on adult alfalfa leafcutting bees (Hymenoptera: Megachilidae)

Chalkbrood is a serious disease of alfalfa leafcutting bee Megachile rotundata (F.) (Hymenoptera: Megachilidae) larvae, causing upward of 20% infection in the field. The causative agent is the fungus Ascosphaera aggregata. This bee is used extensively for alfalfa seed pollination in the United States. Using laboratory bioassays, we previously demonstrated that fungicides can reduce chalkbrood levels in the larvae. Here, we evaluate the toxicity of four fungicides, Benlate, Captan, Orbit, and Rovral, to adult bees by using three different bioassays. In the first test, fungicides were applied to bees' thoraces. In the second test, mimicking foliage residue, a piece of filter paper soaked in fungicide was placed on the bottom of a container of bees. The third test evaluated oral toxicity by incorporating fungicides into a sugar-water solution that was fed to the bees. The filter paper test did not discriminate among the fungicides well, and the oral test resulted in the greatest mortality. Toxicity to males was greater than to females. The use of fungicides for chalkbrood control is a logical choice, but caution should be used in how they are applied in the presence of bees.     

Nesting aggregation as a predictor of brood parasitism in mason bees (Osmia spp.)

1. Parasitism can be an important source of mortality for insect populations; however, we know little about the factors influencing vulnerability of wild bees to parasites. Mason bees (genus Osmia; Hymenoptera: Megachilidae) are important pollinators of crops and wild plants and are vulnerable to attack by brood parasites. High nest densities may increase rates of brood parasitism by attracting disproportionate numbers of parasites. 2. Three years of field observations from multiple sites were analysed to assess whether mason bee brood parasitism increased with host density. Mason bees were allowed to nest in artificial nesting blocks and establish natural variation in nesting density. Nest cells constructed by bees were checked for the presence of parasite eggs. 3. Parasitism of nest cells strongly increased with the number of actively nesting bees at a nesting block. Mason bees showed no preference for nesting in blocks that were occupied or unoccupied by other mason bees. Parasitism also increased with the number of days a nest was provisioned and decreased over the course of the season. Nest cells constructed last in a nest were significantly more parasitised than inner cells, despite being sealed against invasions. 4. These findings show positively density‐dependent parasitism in mason bees. They also suggest that bees terminate parasitised nests, causing parasitised cells to become outermost nest cells – a behaviour that may represent a defence against parasites. Our results have implications for the management of mason bees as agricultural pollinators, as cultivating them at high densities could reduce offspring survival.     

Experience-dependent plasticity in the mushroom bodies of the solitary bee Osmia lignaria (Megachilidae)

All members of the solitary bee species Osmia lignaria (the orchard bee) forage upon emergence from their natal nest cell. Conversely, in the honey bee, days-to-weeks of socially regulated behavioral development precede the onset of foraging. The social honey bee's behavioral transition to foraging is accompanied by neuroanatomical changes in the mushroom bodies, a region of the insect brain implicated in learning. If these changes were general adaptations to foraging, they should also occur in the solitary orchard bee. Using unbiased stereological methods, we estimated the volume of the major compartments of the mushroom bodies, the neuropil and Kenyon cell body region, in adult orchard bees. We compared the mushroom bodies of recently emerged bees with mature bees that had extensive foraging experience. To separate effects of general maturation from field foraging, some orchard bees were confined to a cage indoors. The mushroom body neuropil of experienced field foragers was significantly greater than that of both recently emerged and mature caged orchard bees, suggesting that, like the honey bee, this increase is driven by outdoor foraging experience. Unlike the honey bee, where increases in the ratio of neuropil to Kenyon cell region occur in the worker after emerging from the hive cell, the orchard bee emerged from the natal nest cell with a ratio that did not change with maturation and was comparable to honey-bee foragers. These results suggest that a common developmental endpoint may be reached via different development paths in social and solitary species of foraging bees.     

Novel microsatellite loci reveal high genetic diversity yet low population structure for alfalfa leafcutting bees in North America

The alfalfa leafcutting bee, Megachile rotundata (ALCB) is an economically important pollinator necessary for seed production of the critical forage crop alfalfa, Medicago sativa. The pollinator was accidentally introduced to North America from Europe approximately 70 years ago, and it is primarily produced in Canada and shipped to the United States annually en masse for seed field pollination. We investigate how the large-scale commercial movement of this bee affects the genetic structure of populations in the North American seed growing system and compare the genetic diversity and structure of introduced North American bees with two native European populations. Using 16 newly developed microsatellite loci, we describe the North American population structure of this bee. ALCBs collected from alfalfa seed farms have a degree of genetic variability similar to one native European population, but lower than the second. Considering that the species was accidentally introduced into North America, we anticipated more signature of a founder effect. Despite the level of genetic variability, we found little, if any, genetic structuring across North America, other than that the North American populations were distinct from the European populations sampled. While we detected some sub-structure in North American populations using Bayesian methods, the structuring was without geographic pattern, and we propose it is the result of the intense human management and movement of these bees. The trade and movement of these bees by humans has created a nearly panmictic M. rotundata population across the continent, which has implications relevant to the preservation and conservation of other bee pollinators.