Mechanisms of interspecific competition among an invasive and two native fire ants

The mechanisms of interspecific competition among an invasive and two native Solenopsis fire ant forms were investigated in a series of laboratory experiments. In separate trials each with a different food resource, the native S. geminata × xyloni retrieved the greatest amount of a protein- and lipid-rich artificial food resource and a high protein natural food resource, and the native S. geminata retrieved the greatest amount of a high carbohydrate food resource. In trials investigating aspects of interference competition at the colony level, the invasive S. invicta proved to be initially more aggressive than S. geminata , but less aggressive than S. geminata × xyloni . Solenopsis invicta eventually controlled more of the foraging arenas against both native forms when colonies were equivalent by worker biomass, but not when colonies were equivalent by worker number. When paired with S. invicta , S. geminata suffered a significantly greater proportional reduction in both workers and entire colonies when colonies were initially standardized by worker biomass, but not when colonies were standardized by worker number. When paired with S. invicta , a significantly greater proportional reduction of workers occurred in S. geminata × xyloni , regardless of how colonies were standardized. In pairwise trials at the individual level, majors always exhibited significantly less mortality than minors, regardless of the Solenopsis form. The majors of both native forms suffered significantly less mortality than those of S. invicta . Superiority in colony-level interference ability appears to be an important mechanism allowing S. invicta to displace native Solenopsis forms. The ability of S. invicta to reach high population densities, because of intrinsic biological characteristics or an escape from natural enemies, plays an important contributory role. Similar mechanisms may underlie the success of other invasive ant species.     

Native ant responses to Solenopsis invicta buren reduction using broadcast baits

A pilot study was conducted to investigate the impact of Solenopsis invicta management with an insect growth regulator bait (s-methoprene) on native ant species and to determine the responses of these species to S. invicta reduction. This invasive species alters the diversity and structure of different trophic levels of arthropod assemblages. Despite advances in S. invicta management using biological control agents, poison baits remain as the primary tool for effective fire ant management. However, the effect of these products on native ants is relatively unknown. Understanding these effects is critical to the development of S. invicta management strategies that include conservation of native ants. Native ants compete with S. invicta to some degree and can bolster efforts to release and establish exotic biological control agents to more effectively manage S. invicta. The study was carried out in Mumford, TX. Two treatments were used: a bait treatment that reduced S. invicta densities and a control. The treatments were randomly assigned to 1.33-ha blocks, replicated four times, and periodically inspected using complementary sampling techniques (pitfall traps, baited vials, manual collections, and nest surveys). Sixteen ant species were found among the two treatments. After S. invicta reduction, significant increases in densities of several other ant species were observed. Species within the assemblage shifted from the dominance by S. invicta to the dominance of the native pyramid ant, Dorymyrmex flavus McCook, which showed the most significant increase in bait treated blocks and was found to persist at densities significantly higher than the control for >2 yr after the last bait treatment. A temporary change in diversity was observed, indicating that use of a poison bait for S. invicta management benefited numerous resident species in the ant assemblage.     

Interspecific competition between Solenopsis invicta and two native ant species, Pheidole fervens and Monomorium chinense

This study was designed to understand the effects of the interspecific competition between red imported fire ant, Solenopsis invicta Buren and two native ant species, Pheidole fervens Smith and Monomorium chinense Santschi, by conducting colony interference and individual confrontation tests under laboratory conditions. The colony interference test showed that both native ant species, owing to their numerical advantage, killed the Solenopsis invicta virus-1 (SINV-1)-infected or healthy queens of S. invicta. Significantly less time was required for M. chinense to kill all SINV-1-infected S. invicta compared with the time required to kill the healthy S. invicta. Compared with healthy S. invicta, SINV-1-infected S. invicta spent a longer time eliminating the P. fervens colonies. In confrontation tests, M. chinense killed a significantly higher number of infected S. invicta minors than they did healthy minors, but the number of S. invicta majors (either infected or healthy) killed was substantially less. This study found that the viral infection weakened the competitive ability of S. invicta and made them prone to be eliminated by M. chinense but not by P. fervens.     

Detection of Thelohania solenopsae (Microsporidia: Thelohaniidae) in Solenopsis invicta (Hymenoptera: Formicidae) by multiplex PCR

Oligonucleotide primer pairs were designed to unique areas of the small subunit (16S) rRNA gene of Thelohania solenopsae and a region of the Gp-9 gene of Solenopsis invicta. Multiplex PCR resulted in sensitive and specific detection of T. solenopsae infection of S. invicta. The T. solenopsae-specific primer pair only amplified DNA from T. solenopsae and T. solenopsae-infected S. invicta. This primer pair did not produce any amplification products from DNA preparations from uninfected S. invicta, seven additional species of microsporidia (including Vairimorpha invictae), or Mattesia spp. The Gp-9-specific primers recognized and amplified DNA from Solenopsis xyloni, Solenopsis richteri, Solenopsis geminata, the invicta/richteri hybrid, and monogyne and polygyne S. invicta, but not from T. solenopsae, and, as such, served as a positive control verifying successful DNA preparation. Multiplex PCR detected T. solenopsae in worker fire ants infected with as few as 5000 spores. Furthermore, multiplex PCR detected T. solenopsae in all developmental stages of S. invicta. However, detection could be made more sensitive by using only the T. solenopsae-specific primer pair; ants infected with as few as 10 spores were able to be discerned. Multiplex PCR detection of T. solenopsae offers the advantages of a positive control, a single PCR amplification, detection of all developmental stages, and increased sensitivity and specificity compared with microscopy.     

两种火蚁与黑头酸臭蚁上颚形态及其超微结构观察

应用扫描电镜和光学显微镜观察了红火蚁Solenopsis invicta Buren、热带火蚁Solenopsis geminata Fabricius和黑头酸臭蚁Tapinoma melanocephalum Fabricius的上颚类型及形态特征。头宽和上颚长度测量结果表明:两种火蚁的头宽和上颚大小具有连续性特征,黑头酸臭蚁工蚁仅1个类型,3种蚂蚁中黑头酸臭蚁的上颚最小,其前端具4个锋利切齿叶,后部有一排小而钝的臼齿叶,上颚内缘较光滑。在形态上,红火蚁的大、中、小型工蚁与热带火蚁工蚁的上颚区别不大,表面纹理光滑,都具4个锋利小齿,上颚内缘也比较光滑;热带火蚁兵蚁上颚仅3个小齿且较钝,其上颚内缘凹面比两种火蚁工蚁的深且纹理粗糙,推测红火蚁工蚁不仅用于筑巢,还用于防御,而热带火蚁兵蚁的强壮上颚可能主要用于磨碎食物,而非保卫蚁巢。     

入侵中国大陆的红火蚁的鉴定及发生为害调查

根据形态特征鉴定结果首次证实红火蚁SolenopsisinvictaBuren入侵中国大陆 ,并调查了广东省吴川市红火蚁发生为害情况。调查结果表明 ,发生区内部分地点红火蚁发生密度较高 ,主要发生于较稳定的生态环境中 ,如荒坡、草地、长满杂草的田埂等。红火蚁已对当地农业生产、人们的身体健康、日常生活等造成了不利影响。此外 ,Cytb基因序列分析结果表明 ,采自美国佛罗里达和广东吴川的红火蚁与采自广东 4个地方的热带火蚁S .geminata (Fabr.)两物种间有 61个变异位点 ,种内变异为 0。限制性酶切多态实验 (RFLP)的结果显示 ,BamHI酶在红火蚁的特异扩增片段中有一个识别位点 ,而在热带火蚁中无酶切位点 ;MspI酶在热带火蚁的扩增片段中也有一个识别位点 ,而在红火蚁中无识别位点。有酶切位点的扩增产物在酶切后分别获得近 2 0 0bp与 2 5 0bp的片段各一带。因此 ,用PCR RFLP的方法可以简单快速地鉴别红火蚁和热带火蚁。     

红火蚁及其他两种蚂蚁毒腺细菌鉴定与多样性分析(英文)

【目的】本研究旨在分析红火蚁Solenopsis invicta毒腺细菌群落多样性,并与热带火蚁Solenopsis geminata和聚纹双刺猛蚁Diacamma rugosum比较毒腺细菌群落差异。【方法】采用Illumine Hiseq 2500测序平台对红火蚁(工蚁、有翅蚁和蚁后)、热带火蚁(工蚁)及聚纹双刺猛蚁(工蚁)毒腺细菌群落16S rRNA基因V3-V4区测序,基于测序数据进行生物信息学分析。【结果】变形菌门(Proteobacteria)在红火蚁工蚁、有翅蚁和蚁后以及热带火蚁工蚁毒腺中占优势,而厚壁菌门(Firmicutes)在聚纹双刺猛蚁工蚁毒腺中占优势。与红火蚁工蚁和有翅蚁相比,柔壁菌门(Tenericutes)在红火蚁蚁后毒腺中更丰富。广州红火蚁蚁后毒腺中假单胞杆菌Pseudomonas相对丰度显著高于其在有翅蚁及工蚁中的。螺原体Spiroplasma相对丰度在热带火蚁毒腺中显著高于在聚纹双刺猛蚁工蚁毒腺中的。毒腺中细菌多样性分析发现,芽孢杆菌属Bacillus和乳酸杆菌属Lactobacillus在广西红火蚁工蚁中的相对丰度显著高于在广州红火蚁工蚁中的。然而,乳酸杆菌属细菌在聚纹双刺猛蚁工蚁毒腺中的相对丰度显著高于广西的热带火蚁工蚁毒腺中的。【结论】毒腺细菌组成和多样性在3种不同种类蚂蚁工蚁和红火蚁不同品级中存在差异。     

Aggressive interactions between Solenopsis invicta and Linepithema humile (Hymenoptera: Formicidae) under laboratory conditions

The Argentine ant, Linepithema humile (Mayr), and the red imported fire ant, Solenopsis invicta Buren, are natural agonists in their country of origin. Since the first report of L. humile in California in 1907 its range expanded statewide, displacing native ant species wherever it spread. Since the discovery of established populations of S. invicta in southern California in 1998, it has been restricted to discrete areas of southern California. However, as these discrete populations expand, they are encountering large populations of L. humile, which are effective competitors for available resources and are particularly aggressive in their encounters with other ant species such as S. invicta. Most Dolichoderine ants such as L. humile do not prefer to forage on baits made with defatted corn grit and soybean oil typically used in red imported fire ant control programs. Applications of these baits in areas where distributions of these species overlap might selectively affect populations of S. invicta and give L. humile a competitive advantage. Three laboratory experiments were conducted to determine the competitive outcomes between S. invicta pitted against L. humile: 1) agonistic behavior of workers in small arenas, 2) colony interactions with different population ratios, and 3) the effects of pyriproxyfen on the competitiveness of S. invicta against L. humile. Populations of S. invicta consisting of major workers killed more L. humile than did minors or a mixture of majors and minors. When paired against L. humile colonies consisting of 1,100 workers, colonies consisting of 38 S. invicta workers were easily defeated by L. humile. Colonies consisting of 450 S. invicta workers plugged their nest entrances, but they were ultimately defeated by L. humile after 13 d. The S. invicta colonies consisting of 1,100 workers took control of the bridge connecting the colonies, invaded the L. humile colony, killed the Argentine ant queens, and removed their brood. Pyriproxyfen-treated fire ant workers took significantly longer to chase the Argentine ants from a connecting bridge than did untreated fire ants. Thus, fire ant baits may have long-term effects on intercolonial aggression between S. invicta and L. humile, especially when Argentine ant populations are high in the summer.     

红火蚁与两种本地蚂蚁间的干扰竞争

为了探讨重大入侵生物红火蚁Solenopsis invicta Buren与本地蚂蚁的竞争机制以及红火蚁成功入侵的机理, 本研究以红火蚁和2种本地蚂蚁黑头酸臭蚁Tapinoma melanocephalum (Fabricius)及亮红大头蚁Pheidole fervida Smith为材料, 室内测定了红火蚁分别与黑头酸臭蚁、亮红大头蚁之间在个体水平和种群水平上的攻击性和攻击强度。一对一攻击试验结果表明：红火蚁和黑头酸臭蚁之间攻击级别多集中在Ⅲ级, 即竞争优势明显的红火蚁对黑头酸臭蚁缺乏激烈的攻击, 只是在相互攻击时多摆出威胁姿势; 红火蚁与亮红大头蚁之间攻击性较强, 尤其是红火蚁中型和小型工蚁与亮红大头蚁兵蚁之间的攻击性（3.35和3.30）显著强于红火蚁大型工蚁与亮红大头蚁兵蚁的攻击性（2.70）。群体攻击试验结果表明：与黑头酸臭蚁群体攻击的红火蚁各处理组合中, 无死亡红火蚁出现, 而黑头酸臭蚁死亡率为31.80%; 而与亮红大头蚁群体攻击中, 红火蚁死亡率为0.20%~12.00%, 而亮红大头蚁平均死亡率为49.91%。可见, 红火蚁的群体攻击能力强于黑头酸臭蚁和亮红大头蚁, 其中红火蚁与亮红大头蚁间的相互攻击程度激烈, 死亡率较高, 而与黑头酸臭蚁间的攻击程度较弱, 可能由于黑头酸臭蚁化学防御对本身起到一定的保护作用, 这为进一步加强红火蚁发生区本地蚂蚁优势种--黑头酸臭蚁的保护利用提供理论基础。     

Phylogeographic structure of the fire ant Solenopsis invicta in its native South American range: roles of natural barriers and habitat connectivity

We generated mitochondrial DNA (mtDNA) sequence data from 402 individuals of the fire ant Solenopsis invicta collected from 11 native populations and analyzed these data using a combination of demographic, phylogenetic, and phylogeographic methods to infer features of the evolutionary history of this species. Prior expectations regarding high levels of genetic structure and isolation by distance among populations were supported by the data, but we also discovered several unanticipated patterns. Our analyses revealed a major genetic break between S. invicta mtDNA haplotypes that coincides with the Mesopotamia wetlands region of South America, resulting in two higher level nested clade groupings. In addition, we identified contrasting patterns of genetic differentiation within these two major groups, which may reflect differences in connectivity of suitable habitat in different parts of the native range of S. invicta. Our study represents the first attempt to understand the phylogeographic history of S. invicta across its native range.     

Contrasting exotic Solenopsis invicta and native Forelius pruinosus ants as mutualists with Catalpa bignonioides, a native plant

Abstract. 1. The suitability of the red imported fire ant Solenopsis invicta Buren and a native ant Forelius pruinosus (Roger) as participants in a food-for-protection mutualism with a native nectaried tree Catalpa bignonioides Walter was compared.
2. The mean mortality of folivore larvae of Ceratomia catalpae Boisduval was similar for S. invicta and F. pruinosus although S. invicta attacked fewer caterpillar aggregations and was a devastating pupal predator. Solenopsis invicta also differed from the native ant in that it attacked the parasitoid Cotesia congregata Say, another plant mutualist, and visited extrafloral nectaries less frequently.
3. Habitats invaded by S. invicta are characterised by a scarcity of both herbivores and of beneficial insects that visit extrafloral nectaries. The plants do not require protection, and extrafloral nectaries are visited rarely. Although plants are defended incidentally by S. invicta , the insect-plant mutualism therein is greatly simplified or defunct.     

Use of ribosomal DNA sequence data to characterize and detect a neogregarine pathogen of Solenopsis invicta (Hymenoptera: Formicidae)

A neogregarine parasite of the red imported fire ant, Solenopsis invicta, was discovered recently in Florida and tentatively placed in the Mattesia genus based on morphological characterization. S. invicta infected with this Mattesia species exhibited a characteristic yellowing of the cuticle which was designated Mattesia "yellow-head disease" (YHD). The 18S rRNA gene sequence from Mattesia YHD was elucidated and compared with the neogregarine pathogens, Mattesia geminata and Ophriocystis elektroscirrha. The sequence data support the previous conclusion that Mattesia YHD is a new species that infects S. invicta. Furthermore, high sequence identity between Mattesia YHD, M. geminata (95.7%), and O. elektroscirrha (86.2%) correctly place the YHD organism in the Mattesia genus and Neogregarinorida order. Oligonucleotide primer pairs were designed to unique areas of the 18S rRNA genes of Mattesia YHD and S. invicta. Multiplex PCR resulted in sensitive and specific detection of Mattesia YHD infection of S. invicta.     

不同方法对红火蚁社会型鉴定效果的比较

红火蚁Solenopsis invicta Buren的社会型——单蚁后(Monogyne)和多蚁后(Polygyne)型的鉴定方法众多,对于鉴定方法之间的比较较少。为了探究鉴定红火蚁社会型的有效实验方案,本研究对采集自中国南方的红火蚁种群样品进行了生物学观察,并采用了几种常用的方法对样品社会型进行了测定,此外还对比了4种不同DNA聚合酶在实验中的效果。多重PCR技术(Multiplex Polymerase Chain Reaction)、Gp-9 b等位基因扩增两种方法成功率高,能准确鉴定红火蚁社会型。4对同时扩增B、b等位基因的引物成功率不高。实验结果表明,将多重PCR技术、Gp-9 b等位基因扩增,与生物学观察相结合,能更准确地对红火蚁社会型进行鉴定。在PCR实验中选用具有适度保真性和热启动效果的DNA聚合酶能提高红火蚁社会型鉴定的准确性。     

Experimental evidence that the introduced fire ant, Solenopsis invicta, does not competitively suppress co-occurring ants in a disturbed habitat

1. The fire ant, Solenopsis invicta, is a globally distributed invasive ant that is largely restricted to disturbed habitats in its introduced range. For more than half a century, biologists have believed its success results from superior competitive abilities relative to native ant species, as well as an escape from their natural enemies. 2. We used large volumes of hot water to kill fire ant colonies, and only fire ant colonies, on experimental plots in pastures, and found that populations and diversity of co-occurring ants did not subsequently increase. 3. These results are contrary to classical predictions and indicate that S. invicta is not a superior competitor that suppresses native ants, and that the low diversity and abundance of native ants in degraded ecosystems does not result from interaction with fire ants. Instead, other factors such as prior disturbance and recruitment limitation may be the primary limiting factors for native species in these habitats.     

Similarity in venom alkaloid chemistry of alate queens of imported fire ants: implication for hybridization between Solenopsis richteri and S. invicta in the Southern United States

Both cis- and trans-2-methyl-6-undecylpiperidines, MC11P, have been previously reported as the major components of the venom of alate queens of the imported fire ants, Solenopsis richteri (black) and S. invicta (red). To identify the minor components of venom alkaloids from alate queens and compare the venom alkaloid chemistry of alate queen of their hybrid (S. richteri×S. invicta) with that of the two parental fire ant species (S. richteri and S. invicta), silica-gel short-column chromatography was utilized for separating cis-stereoisomers of venom alkaloids from trans-stereoisomers. GC/MS Analyses of venom-alkaloid chemistry of alate queens demonstrated that fewer alkaloid peaks were detected in the chromatograms of the alate queens compared to those of workers. Three new compounds, 7, 12, and 13, were detected as minor components in the venom of alate queens of all three fire ant species. Alate queens of hybrid fire ants showed cis- and trans-alkaloid patterns similar to those of the parental species. Similarity in venom-alkaloid chemistry of alate queens of S. richteri and S. invicta, and their hybrid may indicate their reproductive compatibility in the hybrid zone in southern United States, where all three species occur sympatrically.     

中国和美国红火蚁毒腺生物碱组分的比较分析

【目的】比较两个入侵地红火蚁Solenopsis invicta毒腺生物碱成分及相对含量的地区间差异。【方法】以在中国广东省惠州、 广州、 深圳、 东莞、 珠海和美国阿拉巴马州采集的红火蚁工蚁为材料, 用正己烷溶剂浸提48 h获得浸提液, 将浸提液进行硅胶柱层析分离, 用气相色谱-质谱联用仪（GC-MS）分析其所含的生物碱成分及其相对含量。【结果】红火蚁毒腺生物碱含顺式生物碱组分和反式生物碱组分。通过总离子图对比, 得到了7种顺式生物碱、 8种四氢吡啶和7种反式生物碱, 并计算得到这些组分的相对百分含量。【结论】中国广东省5个地区红火蚁生物碱组成无差别, 相对含量略有差异, 惠州种群和深圳种群差别最大, 其他地区间没有差别。中美两国入侵地的红火蚁种群生物碱成分种类无差别, 其各个组分之间相对含量略有差异, 美国阿拉巴马州种群与中国深圳种群各组分相对含量差别最大, 与中国广州种群差别最小。另外, 在检测的中国广东样品中, 只确认了红火蚁的存在, 提示杂合蚁与黑火蚁还未传入中国。     

Repellency of callicarpenal and intermedeol against workers of imported fire ants (Hymenoptera: Formicidae)

Callicarpenal and intermedeol are two insect-repellent terpenoids isolated from leaves of American beautyberry (Callicarpa americana L.; Verbenaceae) and Japanese beautyberry (Callicarpa japonica Thunb.). The repellency of these two terpenoids against workers of red imported fire ants, Solenopsis invicta Buren, black imported fire ants, Solenopsis richteri Forel, and a hybrid of these two species was evaluated using digging bioassays. In a multiple choice digging bioassay using two colonies from each species and their hybrid, callicarpenal showed significant repellency at concentration as low as 50 ppm against both red imported fire ant colonies and 6.25 ppm against all black imported fire ant and hybrid colonies. Intermedeol showed significant repellency at concentration as low as 1.50 ppm against both red imported fire ant colonies and 6.25 ppm against all black imported fire ant and hybrid colonies. In total, 15 colonies, five colonies from each species and the hybrid, were tested on callicarpenal and intermedeol at 50 ppm in a two-choice digging bioassay. Both callicarpenal and intermedeol showed repellency against all colonies, and intermedeol showed significantly greater repellency than callicarpenal against both species and their hybrid.     

红火蚁入侵对玉米植株上节肢动物群落的影响

在农业生态系统中,入侵性红火蚁Solenopsis invicta Buren是一种贪婪的节肢动物捕食者,会不加区分地攻击害虫和有益昆虫。本文以玉米地作为研究生境,系统调查并探讨红火蚁入侵对玉米植株上节肢动物群落的影响。结果表明,红火蚁入侵使得玉米地内节肢动物的种类下降了64.7%,而减少的种类主要隶属于半翅目、鳞翅目和双翅目,并且这种负面影响主要体现在玉米生长后期。随着玉米植株上红火蚁数量的增加,相应的节肢动物群落物种丰富度、多样性和均匀度指数减少,生态优势度指数增加。进一步通过系统聚类分析表明,红火蚁发生区玉米植株上节肢动物类群结构在时间序列上波动较大,其入侵已显著影响了生境内节肢动物群落。     

红火蚁入侵对广东多种生境中蚂蚁类群的影响

采用陷阱法和诱饵诱集法研究了深圳红火蚁发生区和未发生区蚂蚁的类群多样性和相似性.结果表明:草坪和荒草地红火蚁发生区域的蚂蚁物种数明显减少,且草坪中蚂蚁种类减少的程度(6种)大于荒草地 (3种).红火蚁入侵后荔枝园、荒草地和草坪的蚂蚁优势种发生了明显改变,红火蚁替代了原来的优势蚂蚁种类,在数量上占据了主导地位,在荒草地和草坪这种优势种的改变更为明显.对蚂蚁类群指数的分析表明:红火蚁入侵荒草地和草坪后蚂蚁类群的多样性、均匀度降低,优势度明显增大;而荔枝园中蚂蚁类群多样性指数、均匀度指数均增大,优势度指数降低.荔枝园、荒草地和草坪的红火蚁发生区和未发生区蚂蚁类群相似性系数不同,分别为0.6316、0.5882和0.2941.     

Isolation, characterization, and molecular identification of bacteria from the red imported fire ant (Solenopsis invicta) midgut

Bacteria were isolated and cultured from the red imported fire ant (Solenopsis invicta) midgut. The small-subunit ribosomal RNA gene, (16s rRNA gene, approximately 1500 bp) was amplified from bacterial genomic DNA using the polymerase chain reaction and consensus sequence primers. Restriction fragment length polymorphism analysis revealed 10 unique profiles, indicating that at least 10 different bacteria are present in red imported fire ant midguts. The 16s rRNA gene sequence was determined for these isolates and queried against the NCBI genetic database. The results identified all isolates to at least the genus level. Antibiotic resistance profiles and biochemical activities were also determined for these species. This work provides the basis for a wider characterization of bacterial distributions in fire ant colonies and provides strains suitable for genetic manipulation to develop novel methods of fire ant control.