Potential Global Range Expansion of the Invasive Fire Ant, Solenopsis invicta

The red imported fire ant, Solenopsis invicta Buren, is an invasive pest that has become widespread in the southern United States and Caribbean after introduction from South America in the 1930s. This species, which has diverse detrimental impacts on recipient communities, was recently discovered in Australia and New Zealand and has the potential to colonize numerous other regions. We used a dynamic, ecophysiological model of colony growth to predict the potential global range expansion of this invasive species. Based on minimum and maximum daily temperatures, the model estimates colony alate production and predicts future geographic range limits. Because S. invicta populations are limited by arid conditions as well as cold temperatures, we superimposed precipitation data upon temperature-based predictions, to identify regions that do not receive enough rainfall to support this species across the landscape. Many areas around the globe, including large portions of Europe, Asia, Africa, Australia, and numerous island nations, are at risk for S. invicta infestation. Quarantine officials should be vigilant for any accidental introductions of this pest in susceptible regions. Costs of eradication increase dramatically as the area of infestation grows, and large infestations may be impossible to eradicate. Other South American Solenopsis fire ants (e.g., S. richteri Forel) may become invasive if the opportunity arises, and our predictions for S. invicta may approximate the potential range limits for these species as well.     

A larval hunger signal in the bumblebee Bombus terrestris

Larvae of Bombus terrestris, a pollen-storing bumblebee, are dependent on progressive provisioning by workers. We test the hypothesis that larval cuticular chemicals can act as a hunger signal. We first show with a new classical conditioning experiment, using a Y-shaped tube, that workers can be trained to prefer the extracts of normally fed larvae over those of starved larvae. This proves the ability of workers to discriminate between larval extracts. Second, we show in a bioassay that workers also use these perceived differences to feed larvae according to their nutritional status. Larval broods sprayed with the extracts of the starved larvae were fed significantly more than larval broods sprayed with the extracts of normally fed larvae or with the solvent (n-pentane) only. We therefore conclude that B. terrestris larvae signal their need for food via their cuticular chemicals, and discuss the extent to which this form of communication could give larvae some control over their development. Received 2 September 2005; revised 11 April; accepted 24 April 2006.     

紫茎泽兰对四川省凉山州共生植物种间联结性及稳定性的影响

紫茎泽兰是中国危害最严重的入侵植物之一。为有效预测和评估紫茎泽兰入侵程度,基于2×2联列表,采用χ~2和W检验,联结系数(AC)、共同出现百分率(PC)、Ochiai指数(OI)、Dice指数(DI)的种间联结性分析和Godron M群落稳定性测定方法,以四川省凉山州危害最严重的入侵植物紫茎泽兰群落为研究对象,分析了西昌市、会理县、会东县、德昌县和普格县紫茎泽兰与其共生植物间的联结性及群落稳定性。结果表明:四川省凉山州与紫茎泽兰共生的植物共有155种,其中草本植物86种,灌木34种,乔木22种,藤本植物10种,蕨类植物2种,苔藓植物1种。χ~2和W检验发现,紫茎泽兰群落主要植物间的总体关联性VR(方差比率)为0.9677,小于1,检验统计量χ~2_(0.95)(50)Wχ~2_(0.05)(50),表明紫茎泽兰群落主要物种间总体表现为不显著负相关。种群间χ~2统计量均小于3.841,说明主要种对间联结性较低,甚至趋于独立,紫茎泽兰群落优势种群对环境的适应性相似甚至相同,但对资源利用存在竞争。种间联结性分析表明,紫茎泽兰群落中20个种对间表现出正相关性,22个种对间则表现出负相关性,或处于完全独立的状态。紫茎泽兰-鬼针草、紫茎泽兰-野艾蒿、紫茎泽兰-马唐和紫茎泽兰-灯笼草种对的共同出现百分率PC值均处于[0.4,0.6)区间内,OI指数和DI指数均大于0.6,一方面说明紫茎泽兰在一定时期内,与鬼针草、野艾蒿、马唐和灯笼草具有相同或相似的生态位需求和对环境的适应性,另一方面说明鬼针草、野艾蒿、马唐和灯笼草等物种对紫茎泽兰抑制其他物种生长特性的抵抗能力较强;群落稳定性分析可知,模型方程与直线方程的交点为51/49,距离稳定交点坐标20/80较远,说明紫茎泽兰群落处于不稳定状态。结论:紫茎泽兰入侵使四川省凉山州原有植物群落处于相对不稳定状态,种间会出现一定程度的分离,以降低竞争强度,从而逐步趋于稳定。该结论可为及早预测和评估紫茎泽兰入侵程度提供一定参考。     

Host preference in Pseudacteon phorid flies: response of P. tricuspis and P. curvatus to black, red and hybrid imported Solenopsis fire ants in multiple choice bioassays

Host preferences in both sexes of Pseudacteon tricuspis Borgmeier (Jaguariuna biotype) and Pseudacteon curvatus Borgmeier (Formosa biotype) and their relative attraction to the imported fire ants (IFA), Solenopsis invicta Buren (red IFA), Solenopsis richteri Forel (black IFA) and S. invicta × S. richteri hybrids (hybrid IFA) were investigated in two separate experiments utilizing multiple choice flight bioassays. The results of both experiments clearly showed that both sexes of the Jaguariuna biotype of P. tricuspis could distinguish among the three IFA species and demonstrated greater preference for hybrid IFA and red IFA. This conclusion is supported by a variety of data collected on the number of fly visits, attack rate, and hovering duration (Experiment 1), and on the number of trapped flies (Experiment 2), which showed that black IFA is the least preferred of the three species. Similar results were recorded for the Formosan biotype of P. curvatus, although the data were not as strongly conclusive. Females of this biotype spent a significantly greater amount of time in hovering mode over red IFA and hybrid IFA compared to black IFA, but the other data were not significant. The red IFA is the natural host of both phorid fly biotypes and our results suggest that both biotypes may have evolved a specialized relationship with red IFA including an ability to discriminate it from related fire ants. These results are discussed in relation to the possible role of fire ant chemicals in mediating host preferences in phorid flies, contributions of male phorid flies to fire ant biocontrol, and the practical implications of the key findings.     

Development of interspecific recognition behavior in the antsManica rubida andFormica selysi (Hymenoptera: Formicidae) reared in mixed-species groups

The purpose of this study was to determine the role of early social experience on the ontogeny of kin and nestmate recognition in ants by means of both behavioral and chemical analysis. Workers of two ant species,Manica rubida (Myrmicinae) andFormica selysi (Formicinae), were reared in homospecific groups (control) or in artificial heterospecific groups (mixed), created less than 5 h after their emergence. Recognition was evaluated between unfamiliar individuals of different species reared in control and mixed groups for periods of 5, 12, 24, 48, and 72 h and 8, 15, 30, 60, or 90 days after emergence. Heterospecifically reared individuals of both species gradually became tolerant of allospecific individuals from control groups. Moreover, homospecifically reared individuals did not aggress allospecific individuals reared in mixed groups. During the course of familiarization between the species, there were modifications of the chemical recognition signals. In mixed groups, hydrocarbon profiles of both species acquire gradually some of the components characteristic of their heterospecific nestmates. These experiments showed that allospecific recognition required the acquisition of a minimal quantity of allospecific cues. The phenomenon provided an another example of the relationship between tolerance and the chemical cues displayed by both species. The results suggested that the individual recognized the allospecific cues borne on each individual's body surface and/or that each individual learned and memorized allospecific cues during its early life. Therefore, each individual might develop a template encoding the allospecific and the conspecific cues to characterize nestmates.     

小黄花茶群落优势木本植物生态位及种间联结性

赤水桫椤国家级自然保护区是小黄花茶物种原产地,近来研究发现小黄花茶种群具有急速衰退的趋势,其物种濒危机制并不清楚。生态位及种间联结性可反映物种利用资源的能力,研究小黄花茶种群生态位及其与伴生种之间的联结性,对探索小黄花茶群落稳定性具有重要意义。采用典型样地调查法对赤水桫椤国家级自然保护区8个小黄花茶集中分布样地进行群落学调查,选择重要值排序前15个优势木本物种,计算生态位宽度(B_S、B_L)、生态位相似比(C_ik)及重叠值(O_ik)、种间联结系数(AC)以及共同出现百分率(PC)等指标,分析物种生态位与物种联结性之间的关系。结果表明：小黄花茶群落木本物种共63种,小黄花茶重要值(0.21)和生态位宽度值(B_S=2.89,B_L=15.76)均为最大。小黄花茶与其它优势种组成14个种对中C_ik≥0.50的有2对,O_ik≥0.50的有3对,优势种生态位相似性和生态位重叠程度均较低。优势种总体联结性和种间联结性呈不显著负关...     

Kneallhazia carolinensae sp. nov., a microsporidian pathogen of the thief ant, Solenopsis carolinensis

A new species of microsporidia is described from adults of the thief ant, Solenopsis carolinensis, collected in Florida, USA. Morphological and genetic characterization of this new species showed that it is most closely related to the genus Kneallhazia and is therefore formally designated, Kneallhazia carolinensae sp. nov. Masses of ovoid, binucleate spores were localized to fat body of adult workers and measured 6.2 ± 0.1 × 3.1 ± 0.1 μm (fresh) and 6.0 ± 0.1 × 3.4 ± 0.1 μm (fixed). These spores were in direct contact with the cell cytoplasm and contained an isofilar polar filament with 12-15 coils. Blastn analysis revealed that the K. carolinensae 16S rDNA sequence exhibited 91% identity with the 16S rDNA gene of K. solenopsae. The morphological and sequence data support the conclusion that K. carolinensae is a novel microsporidian species distinct from K. solenopsae.     

广西银竹老山资源冷杉群落乔木优势树种生态位与种间联结

群落的物种组成、种间关系及稳定性影响着濒危植物的个体生存与种群动态,开展相关研究对深入认识濒危植物的濒危机制,及科学合理制定解濒策略具有重要价值。研究基于资源冷杉的模式标本产地广西银竹老山资源冷杉国家级自然保护区7个资源冷杉群落固定样地的调查数据,运用生态位测定、方差比率法(VR)、χ²检验、联结系数(AC)和Spearman秩相关检验等方法,分析群落重要值排名前15的乔木优势树种的生态位特征与种间联结性。结果表明:(1)在乔木层中生态位宽度较大的优势树种依次为多脉青冈、资源冷杉、大屿八角、木荷、云南桤叶树与灯笼树;(2)优势树种间的生态位重叠均值为0.699,生态位重叠指数普遍较大,乔木优势树种对环境或资源需求的相似性较大,种间竞争较强,种间关系不稳定。其中,资源冷杉与其它优势树种组成 14个种对中生态位重叠值O_ik≥0.50的有8对,优势树种生态位重叠程度较高,种间竞争较激烈;(3)乔木优势树种总体联结性和种间联结性表现为不显著正联结,暗示银竹老山的资源冷杉群落处于动态发育的演替早期阶段。(4)χ²检验、种间联结系数(AC)和Spearman秩相关检验结果均显示,多数种对间呈不显著联结,种间联结性较弱。(5)优势树种的AC值、Spearman秩相关检验与生态位重叠值之间呈极显著正相关(P＜0.001)。研究显示,广西银竹老山资源冷杉与其优势伴生树种的种间关联性较弱,各物种间呈独立分布格局,资源冷杉群落稳定性较弱。因此,建议加强对保护区内资源冷杉群落原生境的保护,同时开展资源冷杉种群的长期动态监测工作。     

Foraging behavior as a determinant of asymmetric competitive interaction between two ant species in a tropical agroecosystem

This work is concerned with elucidating competitive interactions between two neotropical ants, Solenopsis geminata and Pheidole radoszkowskii, focusing on their foraging behavior. When released from competition from P. radoszkowskii, S. geminata increased its foraging activity. On the other hand, when released from competition from S. geminata, P. radoszkowskii did not respond, demonstrating asymmetric competition between the two species. Foraging experiments showed that P. radoszkowskii is more efficient at finding food resources, whereas S. geminata is better at defending the resources once they are encountered. These differences in foraging behavior appear to permit the coexistence of these two species. The practical implications of the results for the management of ant communities in tropical agroecosystems is discussed with respect to the potential use of ants as natural enemies.     

浙江省红楠生境地群落数量分类和环境解析

为探讨群落结构与环境因子对红楠Machilus thunbergii在浙江省分布及发展的影响,采用双向指示种分类(TWINSPAN)、典范对应分析(CCA)并结合种间联结分析,对浙江省172个红楠生境地群落进行数量分类排序与环境解析。结果表明:(1)TWINSPAN将172个样地群落分成8个群落类型,红楠在群落中为优势种或主要伴生种。群落类型的不同是影响红楠生长及更新的重要原因。(2)海拔高度及坡度是决定红楠分布及发展的主导环境因子。红楠作为优势种的生境地主要特征为海拔900m以下、坡度35°以下。(3)甜槠(Castanopsis eyrei)、青冈(Cyclobalanopsis glauca)、木荷(Schima superba)为群落中的稳定优势种,种间联结结果显示与红楠均为显著正关联。     

Diet does not affect intercolonial fighting in Leptothoracine ants

Summary An experiment examined the effects of diet on brood rearing in colonies ofLeptothorax ambiguus andL. longispinosus and on fighting between colonies of the two species. Colonies fedDrosophila and honey reared more pupae than colonies fed the Bhatkar and Whitcomb (1970) diet. However, diet had no effect on intercolonial fighting.     

昆明红火蚁种群发生特征

【目的】2013年10月云南省元谋县首次发现红火蚁。掌握红火蚁蚁巢各品级发生动态,能为当地红火蚁的防控提供技术支撑。【方法】2015年1—12月,在昆明宜良县对红火蚁蚁巢取样、分离,红火蚁取样、称重,统计红火蚁各品级的头数。【结果】地上蚁巢红火蚁蚁群数量发生高峰期在8—9月,其次是3—4月。蚁后数量比例高峰在3—4月;有翅雌蚁比例高峰在4月,其次是7月;有翅雄蚁比例高峰的在5月,其次是9月;生殖蚁幼虫和蛹比例高峰的3、4和12月。地上蚁巢工蚁、兵蚁、职能蚁幼虫和蛹数量发生的高峰期在8—9月,发生小高峰期在4月。【结论】昆明红火蚁蚁群数量动态有2个峰值,第一个峰值为8—9月,以职能蚁防治为主;第二个蜂值3—4月,以生殖蚁和职能蚁防治为主。该结果为昆明红火蚁防控技术提供了数据支撑。     

Early learning of volatile chemical cues leads to interspecific recognition between two ant species

Nestmate recognition in social insects generally involves matching a label to the template that is acquired through the early learning of non-volatile cuticular hydrocarbon cues. However, a possible role of the volatile chemical cues that exist in the nest, and which may also affect template formation, has not been studied. We investigated this possibility using experimental mixedspecies groups composed of the two ant species Manica rubida and Formica selysi. The experimental set-up either allowed full contact between workers of the two species or interspecific contact was hindered or prohibited by a single or a double mesh. After three months, workers of M. rubida ants were selected as focal ants for aggression tests including the following target ants: F. selysi workers from the same mixed-species group (for each of the three rearing conditions) or from a single-species group (control). Workers of M. rubida were always amicable towards their group-mates, irrespective of the experimental group (contact, single or double mesh). However, M. rubida that were not imprinted on F. selysi, expressed high levels of aggression towards the non-familiar F. selysi workers. The finding that F. selysi workers in the mixed-species groups appeared familiar to their M. rubida group-mates even without physical contact between them, suggests that the volatile cues produced by F. selysi affected nestmate recognition in M. rubida. In an attempt to identify these volatile cues we performed SPME analysis of the head space over groups of F. selysi workers. The findings revealed that F. selysi Dufour’s gland constituents, with undecane as the major product, are released into the head space, rendering them likely candidates to affect template formation in M. rubida. Analysis of Dufour’s gland secretion of F. selysi revealed a series of volatile alkanes, including undecane as a major product. These alkanes were not present in the glandular secretion of M. rubida, whose secretion was mainly composed of isomers of farnesene. We therefore hypothesize that callow M. rubida workers in the mixed-species groups had become imprinted by the above alkanes (in particular undecane, being the major heterospecific volatile in the head space) and incorporated them into their own template. Received 18 October 2007; revised 2 January 2008; accepted 7 January 2008.     

Zombie fire ant workers: behavior controlled by decapitating fly parasitoids

Laboratory observations were conducted on four separate red imported fire ant, Solenopsis invicta, colonies that contained workers parasitized by the decapitating fly, Pseudacteon tricuspis. Parasitized S. invicta workers remained inside the nest during parasitoid larval development and left the nest approximately 8 – 10 hours before decapitation by the parasitoid. When parasitized ants left the nest, they were highly mobile, were responsive to tactile stimuli, and showed minimal defensive behavior. Ants ultimately entered into a grass thatch layer, where they were decapitated and the fly maggots pupariated. This study reveals that parasitized ants exhibit behaviors that are consistent with host manipulation to benefit survival of the parasitoid. Received 9 November 2006; revised 26 January 2007; accepted 7 February.     

不同土壤水盐条件下多枝柽柳(Tamarix ramosissima)对胡杨(Populus euphratica)幼苗的影响

目前胡杨更新困难,种群处于退化阶段,而与其生态位高度重叠的多枝柽柳却在扩张。为探讨多枝柽柳对胡杨生长的影响,本研究设置了3个水平的水分、盐分梯度,对胡杨进行了单种和混种的盆栽控制实验,通过测定胡杨幼苗的生长和存活状况,分析不同水、盐梯度下多枝柽柳如何影响胡杨生长。结果表明:(1)多枝柽柳伴生降低当年生胡杨幼苗的存活率,随着水分条件改善,胡杨存活率提高,而盐分对存活率没有显著的影响。(2)水分、盐分和伴生模式几个因子对胡杨的生长特征的影响存在显著的交互作用(P<0.05)。各水盐条件下,多枝柽柳会不同程度降低胡杨幼苗的株高、主根长和地上地下生物量,而根冠比增大。混种条件下,胡杨幼苗对水盐的响应更为敏感。(3)相对竞争强度对水盐环境有明显的响应(P<0.05),随水分条件改善,地上、地下相对竞争强度降低。多枝柽柳对胡杨的生长产生不良影响的机制是通过快速消耗土壤的水分,从而导致胡杨幼苗水分亏缺。土壤水分条件是胡杨和多枝柽柳幼苗共存的关键因素,在水分供给不足的情况下,对水分偏好的差异导致胡杨无法通过实生苗进行有效的更新从而加剧胡杨种群的衰退,而多枝柽柳更为耐旱的特性使其逐步占据河岸的生境。我们的研究结果强调了两个树种对环境因子的适应性差异决定了河岸带植被发育过程中植物-土壤的相互作用导致胡杨在演替过程中表现出的衰退现象。     

A gregarine parasite ofLeptothorax ants from North America

Summary A gregarine parasite (Neogregarinida, Ophryocystidae) ofLeptothorax ants was found near West-Yellowstone, Montana, USA. Infested pupae are characterized by grey to black coloration, irregular pigmentation of compound eyes, and toothless mandibles. The pathogenic effects closely resemble those in the fire ant,Solenopsis geminata, when infested byMattesia geminata. Infested pupae die. The infection can be transmitted to healthy colonies and to differentLeptothorax species by feeding them with infested pupae.     

Enhanced seed development in the interspecific cross Allium cepa x A. sphaerocephalon through ovary culture

Allium sphaerocephalon pollen tubes grew into styles and penetrated micropyles of Allium cepa, but ovules started to degenerate about 16 days after pollination and no seeds developed. Seeds developed in vitro in ovaries excised from flowers 4 and 7 days after pollination. Seven weeks after culture initiation, seeds had grown in 4 of 96 excised ovaries, cultured on BDS medium supplemented with GA₃. Although the culture medium supported seed maturation within excised ovaries of self-pollinated A. cepa flowers, no viable hybrid seeds were recovered from crosses with A. sphaerocephalon. Extended post-fertilization barriers may have restrained development of hybrid embryos in vitro. Ovary culture followed by in ovulo embryo rescue may be feasible for distant-species hybridization in Allium.