The ecological differentiation of asexual lineages of cotton aphids: alate behaviour, sensory physiology, and differential host associations

The cotton aphid ( Aphis gossypii Glover) is a cosmopolitan pest species consisting of various host plant-associated lineages that appear to have different patterns of insecticide resistance, electrophoretic banding, and reproductive output across alternative host species. Debate continues as to whether these differences represent intraspecific variation or indicate a complex of cryptic or sibling species. We studied the host plant-related ecology of two asexual lineages of A. gossypii associated with the families Malvaceae and Cucurbitaceae, respectively, in particular the host plant finding and acceptance processes of the alate forms. The two lineages proved to be differentiated across host plants in terms of: (1) their landing and settling behaviour, nymphal production rate, and subsequent colony establishment (i.e. nymphal survival and development) and (2) their sensory abilities in relation to host plant-derived odours. Furthermore, genetic structuring according to host plant type was detected using the gene for elongation factor 1-α. The magnitude of the genetic differentiation across lineages was low, perhaps indicating a relatively recent divergence. The results demonstrate: (1) the presence of (at least) two cryptic species within the current definition of A. gossypii , as anticipated in previous studies, and (2) the practicalities of using a multidisciplinary approach to understanding the 'limits' of asexual species. If sexuals can be generated from each of these lineages, this conclusion will be open to further testing.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 503–519.     

Elevated atmospheric carbon dioxide and ozone alter soybean diseases at SoyFACE

Human driven changes in the Earth's atmospheric composition are likely to alter plant disease in the future. We evaluated the effects of elevated carbon dioxide (CO₂) and ozone (O₃) on three economically important soybean diseases (downy mildew, Septoria brown spot and sudden death syndrome‐SDS) under natural field conditions at the soybean free air concentration enrichment (SoyFACE) facility. Disease incidence and/or severity were quantified from 2005 to 2007 using visual surveys and digital image analysis, and changes were related to microclimatic variability and to structural and chemical changes in soybean host plants. Changes in atmospheric composition altered disease expression, but responses of the three pathosystems varied considerably. Elevated CO₂ alone or in combination with O₃ significantly reduced downy mildew disease severity (measured as area under the disease progress curve‐AUDPC) by 39–66% across the 3 years of the study. In contrast, elevated CO₂ alone or in combination with O₃ significantly increased brown spot severity in all 3 years, but the increase was small in magnitude. When brown spot severity was assessed in relation to differences in canopy height induced by the atmospheric treatments, disease severity increased under combined elevated CO₂ and O₃ treatment in only one of the 3 years. The atmospheric treatments had no effect on the incidence of SDS or brown spot throughout the study. Higher precipitation during the 2006 growing season was associated with increased AUDPC severity across all treatments by 2.7 and 1.4 times for downy mildew and brown spot, respectively, compared with drought conditions in 2005. In the 2 years with similar precipitation, the higher daily temperatures in the late spring of 2007 were associated with increased severity of downy mildew and brown spot. Elevated CO₂ and O₃ induced changes in the soybean canopy density and leaf age likely contributed to the disease expression modifications.     

Attack, escape and predation rates of larvae of two aphidophagous ladybirds during conspecific and heterospecific interactions

The attack, escape and predation rates for larvae of aphidophagous ladybird Propylea dissecta (Mulsant) and Coccinella transversalis Fabricius were quantified as a potential mechanism leading to the differences in the incidence of cannibalism and intraguild predation. These rates were compared at four larval instars within and between the species. The attack rates of larvae of C. transversalis were significantly higher than those of P. dissecta towards conspecific and heterospecific victims. For both species, third instars exhibited maximum tendency to attack. Escape rates in C. transversalis were higher than P. dissecta. In P. dissecta, the second instars made a greater number of escapes than other conspecific instars after being attacked by same stage cannibal or heterospecific predator. In P. dissecta, first instars suffered maximum mortality due to cannibalism and intraguild predation by conspecifics and heterospecifics of the same and older developmental stage. No larvae of C. transversalis were eaten by P. dissecta of the same stage. These results suggest that the larvae of P. dissecta were more often potential cannibals than intraguild predators, while the reverse was the case in C. transversalis. Based on this finding, it could be predicted that in patchy prey habitats, high rates of larval cannibalism in P. dissecta would occur with a high risk of cannibalism of first instars. Larvae of C. transversalis would respond as intraguild predators, while those of P. dissecta as intraguild prey. The greater size and walking activity of C. transversalis could be possible reason for this tendency.     

多异瓢虫对瓜蚜为害后植物挥发物的行为反应及挥发物成分分析

为明确寄主植物挥发物在多异瓢虫Hippodamia variegata (Goeze)搜索猎物过程中的作用, 采用Y型嗅觉仪测定了多异瓢虫成虫对来自瓜蚜Aphis gossypii Glover、 健康植株、 有蚜植株及蚜害植株本身的挥发物的行为反应。结果表明： 高密度蚜虫（≥700头/L）、 有蚜植株以及密度≥400头/盆的蚜虫为害诱导的黄瓜挥发物和密度≥200头/盆的蚜虫为害诱导的搅瓜挥发物对多异瓢虫成虫具有明显的引诱作用, 而低密度蚜虫（≤500头/L）和健康植株挥发物没有引诱作用。应用动态顶空收集法提取健康植株、 有蚜植株及蚜害植株的挥发物, 进行气质联用仪分析鉴定。结果表明, 从黄瓜健康植株、 蚜害植株和有蚜植株中分别鉴定出8, 12和18种挥发物, 主要组分为十八烯、 E-5-二十碳烯、 正十六烷和正十七烷, 诱导出的新组分为对二甲苯、 邻二甲苯、 正十三烷、 α-法呢烯、 雪松醇、 正十八烷、 正二十六烷及7种未知种类; 从搅瓜健康植株、 蚜害植株和有蚜植株分别鉴定出11, 18和20种挥发物, 主要组分为石竹烯、 十八烯、 正十六烷和正十七烷, 诱导出的新组分为苯乙烷、 对二甲苯、 间二甲苯、 α-蒎烯、 正十四烷、 长叶烯、 α-石竹烯及2种未知种类。上述结果为进一步研究挥发物中引诱多异瓢虫的有效组分奠定了必要的基础。     

Information‐theory‐based model selection for determining the main vector and period of transmission of Potato virus Y

Potato virus Y (PVY, genus Potyvirus, family Potyviridae) is transmitted non‐persistently by aphids. It causes major losses in potato production (Solanum tuberosum), especially following seed tuber‐borne infection of plants. To limit the risk of PVY infection, seed potato production is located preferably in regions where vector pressure is low. The northern‐most high‐grade seed potato production area (HG zone) of Europe is in Finland. The aim of this study was to determine the incidence of aphid species with documented ability to transmit PVY and to use a modelling approach to determine their relative importance as vectors of PVY in the HG zone of Finland. Winged aphids were caught from six to seven potato fields in each of three growing seasons (2007–09) using yellow pan traps that were examined twice a week. Identification of more than 30 000 individuals indicated that 37% of the aphids belonged to nine species reported to transmit PVY. Incidence of PVY in seed lots was low (0–5.6%) and the seasonal increase of PVY incidence was also low in the potato crops. No potato‐colonising aphids were found on the plants in any of the years. The seasonal increase in PVY incidence was modelled using aphid counts in traps, the relative vector efficiencies of the aphids, virus resistance of cultivars, and the initial infection rate of the seed tubers as explanatory variables in generalised linear mixed modelling. Akaike's information criterion was employed to find the best set of explanatory variables for PVY in harvested tubers. Results of this modelling approach showed that the incidence of seed‐borne PVY infection and the early‐season vector flights are the most important factors contributing to the incidence of PVY in the yield. Compared to models with data from all potential vector species, models containing data from Aphis fabae only showed a better model fit with regard to the incidence of PVY in the harvested tubers. The explanatory power of the models was lost when A. fabae was omitted from the vector data, suggesting that other species play a negligible role as vectors of PVY in the HG zone of Finland. Results can be used to devise appropriate strategies for enhanced control of PVY.     

作物多样性对大豆蚜的控蚜效应

【目的】研究大豆蚜发生为害及大豆与多种作物间邻作种植对大豆蚜的控制作用,为大豆蚜的可持续综合治理提供理论依据。【方法】采用系统调查的方法,研究大豆蚜和天敌田间种群动态;通过田间罩笼、人工接蚜和释放天敌的方法,研究捕食性天敌对大豆蚜种群的控制作用;在佳木斯地区进行大豆与早熟马铃薯间作,牡丹江地区进行黄瓜-大豆-玉米、甜葫芦-大豆-玉米、烟草-大豆-香瓜、甜菜-大豆-玉米等多作物带状穿插种植模式,以单作大豆田为对照,对不同种植模式的大豆田大豆蚜与天敌进行调查,研究作物多样性对大豆蚜的控制作用。【结果】2009年6月中下旬大豆蚜开始侵入大豆田,3~5周后田间有蚜株率达到100%,大豆蚜种群发生高峰期在7月下旬至8月上旬,9月上旬在田间逐渐消失。草蛉、瓢虫和寄生蜂等为蚜虫天敌优势种;按大豆蚜与天敌数量之比700︰1,释放异色瓢虫和叶色草蛉成虫7 d后,蚜虫种群减退率分别为54.78%和78.79%;大豆与早熟马铃薯间作,在大豆蚜种群迅速增长期早熟马铃薯收获(7月20日)后第5天,豆田蚜虫天敌总数是收获前的2.6倍,与同期单作大豆田相比,间作田大豆蚜种群数量降低了51.3%。大豆与甜葫芦、香瓜、烟草和玉米等作物进行多样性间作种植,在大豆蚜田间发生高峰期,单作豆田益害比为1︰65.2,多样性种植区的大豆田益害比为1︰26~1︰42,与单作大豆田相比,间作田大豆蚜种群数量降低40.7%~83.5%。【结论】2009年大豆蚜的种群高峰期为8月3日,田间的天敌优势种类为草蛉、瓢虫和寄生蜂。早熟马铃薯与大豆间作,在大豆蚜种群迅速增长期间收获早熟马铃薯,大量蚜虫天敌转移至间作的大豆田,从而形成对大豆蚜的控制。大豆与其它经济作物间邻作,大豆田天敌昆虫与蚜虫的益害比明显提高,表明利用农田作物多样性能充分发挥自然天敌的生物控害作用。     

Seasonal occurrence of Aphis glycines and physiological responses of soybean plants to its feeding

The soybean aphid Aphis glycines Matsumura （Hemiptera： Aphididae） is an important pest of soybean in China. To monitor and manage this pest effectively it is neces-sary to understand its population dynamics and demographics, as well as the physiological responses of soybean plants to its feeding. In this study, using field surveying and suction-trap monitoring, we investigated the population dynamics of the soybean aphid in Xiuyan County, Liaoning Province in northeastern China during 2009-2012. The results indicatedthat the population dynamics of the soybean aphid followed a unimodal curve distribution, with the insect generally colonizing soybean fields from the middle of June to early Julyand the population reaching a peak between early July and early August. On the whole, soybean aphids occurred in suction-traps at least 2 weeks earlier than they were foundin field surveys. A total of 72 alates were collected by suction-trapping over the 4 years, with the earliest alate captures occurring on 28 May in 2009, 2011, 2012 and 4 June in 2010. The life table parameters clearly showed that this aphid had a short doubling time （4.73 ± 0.21 days）, and 7.36± 0.98 nymphs were produced by a soybean aphid adult during its lifetime （13.57 ± 0.30 days）. Finally, biochemical assays indicated that the amount of malondialdehyde and the activities of four defense-related enzymes in soybean leavessignificantly changed between 0 day and 7 days of aphid infestation. Polyphenol oxidase （PPO） and catalase （CAT） activities increased more dramatically after 1 day of aphid feed-ing. In addition, significantly higher levels of superoxide dismutase and CAT were found after aphid feeding for 7 days, whereas there was no significant change in the activitiesof peroxidase and PPO. Consequently, this study will be beneficial in determining the seasonal occurrence of the soybean aphid and selecting insect-resistant soybean varieties,and thus in developing a theoretical framework for appropriate management strategies.     

蚜属轭蚜亚属的研究及一新种记述(同翅目:蚜科)

本文记述世界范围蚜属的轭蚜亚属１１种,其中包括１新种,地肤轭蚜Ａｐｈｉｓ （Ｚｙｘａｐｈｉｓ）ｋｏｃｈｉａｅ Ｚｈａｎｇ ｅｔ Ｚｈａｎｇ,ｓｐ．ｎｏｖ．。给出分种检索表。该亚属为中国新纪录。模式标本存放在中国科学院动物研究所标本馆。地肤ｐｈｉｓ（Ｚｙｘａｐｈｉｓ）ｋｏｃｈｉａｅ Ｚｈａｎｇ ｅｔ Ｚｈａｎｇ,ｓｐ．ｎｏｖ．,（图１～６）正模,无翅孤雌,Ｎｏ．Ｙ７７０１－２－其余同正模。中与Ａ．（     

棉蚜DNA多态性RAPD PCR分析(英文)

应用RAPD PCR技术研究了不同寄主和不同季节棉蚜的DNA多态性。从 2 0种随机引物中筛选出 3种引物 ,用它们的扩增结果进行Nei的遗传距离计算 ,并根据遗传距离对所研究的棉蚜种群做聚类分析。结果表明南京地区花椒上的棉蚜与其它 4种寄主上的棉蚜在DNA水平有明显的分化。聚类分析表明 ,棉蚜季节性种群可分为 3大类群 ,即春、秋季黄色型 ,春、秋季绿色型和黄色小型蚜 (伏蚜 )。而小型蚜的遗传关系与春、秋季绿色型最为接近。