应用多元 PCR 技术对我国红火蚁社会型的鉴定

红火蚁 Solenopsis invicta Buren 蚁群存在着单后型和多后型。不同型的红火蚁在行为及生态上存在着较大的差异,因此社会型的鉴别是一个地区制定正确的红火蚁监控技术的关键步骤。本文利用多元 PCR 技术首次对采自我国 4 省 16 个县(市、区)的 120 个红火蚁蚁群的社会型进行了鉴别。结果表明：我国的红火蚁多后型与单后型共存,但以多后型为主。多后型与单后型的比约为 4∶1 (97∶23),但会因地区的不同而异： 如广东多后型与单后型的比例最低,约为 3∶1 (66∶20),而广西的多后型与单后型的比为 7∶1 (21∶3)。最后,根据我国红火蚁的发生危害情况对这些结果进行了讨论。     

红火蚁的社会型及其相关基因Gp-9的研究综述

红火蚁Solenopsis invicta Buren的蚁巢具有2种基本的社会组织形态:单后型和多后型。蚁巢中蚁后的数量是由工蚁和蚁后的基因型共同决定的。红火蚁的Gp-9基因编码一种气味结合蛋白并控制这种社会多态性的表达。Gp-9基因的发现首次证明单个基因在昆虫复杂的社会行为中起关键的作用。从红火蚁的社会型特征、Gp-9基因与不同社会型的关系以及Gp-9基因的相关研究对该领域的研究进展进行综述。     

A simple genetic basis for complex social behaviour mediates widespread gene expression differences

A remarkable social polymorphism is controlled by a single Mendelian factor in the fire ant Solenopsis invicta. A genomic element marked by the gene Gp‐9 determines whether workers tolerate one or many fertile queens in their colony. Gp‐9 was recently shown to be part of a supergene with two nonrecombining variants, SB and Sb. SB/SB and SB/Sb queens differ in how they initiate new colonies, and in many physiological traits, for example odour and maturation rate. To understand how a single genetic element can affect all these traits, we used a microarray to compare gene expression patterns between SB/SB and SB/Sb queens of three different age classes: 1‐day‐old unmated queens, 11‐day‐old unmated queens and mated, fully reproductive queens collected from mature field colonies. The number of genes that were differentially expressed between SB/SB and SB/Sb queens of the same age class was smallest in 1‐day‐old queens, maximal in 11‐day‐old queens and intermediate in reproductive queens. Gene ontology analysis showed that SB/SB queens upregulate reproductive genes faster than SB/Sb queens. For all age classes, genes inside the supergene were overrepresented among the differentially expressed genes. Consistent with the hypothesized greater number of transposons in the Sb supergene, 13 transposon genes were upregulated in SB/Sb queens. Viral genes were also upregulated in SB/Sb mature queens, consistent with the known greater parasite load in colonies headed by SB/Sb queens compared with colonies headed by SB/SB queens. Eighteen differentially expressed genes between reproductive queens were involved in chemical signalling. Our results suggest that many genes in the supergene are involved in regulating social organization and queen phenotypes in fire ants.     

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。     

Venom alkaloids of monogyne and polygyne forms of the red imported fire ant, <Emphasis Type="Italic">Solenopsis invicta</Emphasis>, in Taiwan

Both monogyne and polygyne colonies of Solenopsis invicta now occupy Taiwan. Although venom alkaloids of these ants have been described and synthesized, we here report on a quantitative analysis of the two social forms for the first time. The alkaloids were studied by gas chromatography coupled to mass spectrometry (GC-MS), and six major venom alkaloids were detectable in both types of workers. Both C₁₃:C_13:1 and C₁₅:C_15:1 ratios in alkaloid venom of monogyne workers were statistically higher than that of polygyne workers, but the sum of proportions of unsaturated alkaloids of polygyne workers was significantly higher than that of monogyne workers, regardless of growth temperature, sampling seasons or geographic location. Results of this study demonstrate that the difference in the proportions of unsaturated alkaloids and the ratios of C₁₃:C_13:1 and C₁₅:C_15:1 alkaloids might be a good indicator for differentiating monogyne and polygyne forms of S. invicta. Received 20 February 2008; revised 4 July 2008; accepted 5 August 2008.     

红火蚁多蚁后型种群有效蚁巢局域分布的空间相关性

应用地统计学的方法分析了红火蚁多蚁后型种群有效蚁巢的空间变异规律,建立了多个间隔距离与半方差值的球状模型.对吴川市调查样地的研究表明, 多个样地不同方向上红火蚁有效蚁巢不同间隔距离上的半方差值呈明显规律性变化,表现为随着间隔距离的增大,半方差值增大,具有空间依赖性.其5个球状模型的变程分别为9.1、7.6、23.5、7.5和14.5 m,平均为12.4 m.在这些距离内的抽样空间上任何两点红火蚁有效蚁巢数量间存在相关关系.所建模型块金常数占基台的比例,即空间不连续性较大,分别为0.7034、0.9247、0.4398、1.1196和0.4624,表明红火蚁有效蚁巢分布存在一定的空间随机性和结构性.深圳市的5块样地10个方向上有7个方向半方差值随间隔距离呈明显规律性变化,表现为空间依赖性,变程分别为14.5、11.2、10.8、17.6、11.3、9.9和12.8 m,平均为12.6 m.     

Interaction of an entomopathogen with an insect social form: an epizootic of Thelohania solenopsae (Microsporidia) in a population of the red imported fire ant, Solenopsis invicta

This is the first report of Thelohania solenopsae infections in monogyne (single-queen) Solenopsis invicta colonies in the field. In a 0.2-ha plot near Baton Rouge, Louisiana, inter-colony prevalence was 63% infection in June, 1999, when the population was 100% monogyne. In February, 2000, 21% of 33 monogyne and 90% of 10 polygyne colonies were infected. By May, 2001, the polygyne colonies had disappeared and only one of 34 monogyne colonies was infected, the final detection of T. solenopsae in the plot. Colony size did not differ significantly among the four types (monogyne versus polygynexinfected versus uninfected).     

Unusual Behavior of Polygyne Fire Ant Queens on Nuptial Flights

This study reports previously undescribed behavior of fire ant queens (Solenopsis invicta) on their nuptial flights. We captured large numbers of alate (winged) queens flying at low altitudes in dense swarms that were virtually devoid of males. We assayed the genotypes of these alate queens at the locus Gp-9, which exhibits strong genotype frequency differences between monogyne (single-queen) and polygyne (multiple-queen) populations, and found that almost all of these low-flying queens originated from polygyne colonies. Comparisons of mtDNA haplotype distributions of these queens to those of alates leaving polygyne nests suggest that the flying queens had not dispersed more than a few hundred meters. Moreover, the proportion of flying queens that were mated did not differ significantly from the proportion of reproductive queens that were mated within the same sites. Thus the flight behavior appears to occur subsequent to mating. We suggest that the flying queens are sampling the local environment in order to select a suitable landing site. Such a site would contain established polygyne nests into which the queens may be adopted as new reproductives.     

Successful establishment of the invasive fire ant Solenopsis invicta in Taiwan: insights into interactions of alternate social forms

Aim Understanding the factors underlying the successful establishment of invasive ant species is critical for developing quarantine strategies to prevent additional invasions as well as for determining how such species overcome the selective pressures in invaded areas. Although several studies have revealed differences in the social organization and population genetics of invasive ants in their native and introduced ranges, few studies have considered the potential interactions between alternate social forms within newly‐invaded areas simply because many invasive ants are characterized as polygyne or unicolonial. Location Taoyuan and Chiayi County, Taiwan. Methods Both social forms (polygyne and monogyne) of the red imported fire ant, Solenopsis invicta, occur in two separately invaded areas in Taiwan (Taoyuan and Chiayi). We employed intensive sampling methods and diagnostic polymerase chain reaction assays to determine the distribution of these two social forms in both infested areas in Taiwan. Results The distribution of social forms differs dramatically between the two infested areas, consistent with different invasion histories regarding the original make‐up of individuals comprising the initial founder group. The Taoyuan population likely was colonized initially by ants of both social forms, with the subsequent spread characterized by continuous outward movement of the two forms, particularly the monogyne form. In contrast, the initial founders of the Chiayi population likely were of the polygyne social form only, suggesting the monogyne social form in this population appeared only recently and likely arose directly from polygyne queens converting to the alternate social form. Main conclusions Our results provide detailed insights into the invasion history of S. invicta in Taiwan and suggest that the distinct reproductive biology of the two social forms may have shaped the current distribution of S. invicta in these infested areas and that the dynamics of two forms may affect the long‐term persistence and potential for spread of this pest ant species.