Bridgehead effect and multiple introductions shape the global invasion history of a termite.

Native to eastern Asia, the Formosan subterranean termite Coptotermes formosanus (Shiraki) is recognized as one of the 100 worst invasive pests in the world, with established populations in Japan, Hawaii and the southeastern United States. Despite its importance, the native source(s) of C. formosanus introductions and their invasive pathway out of Asia remain elusive. Using ~22,000 SNPs, we retraced the invasion history of this species through approximate Bayesian computation and assessed the consequences of the invasion on its genetic patterns and demography. We show a complex invasion history, where an initial introduction to Hawaii resulted from two distinct introduction events from eastern Asia and the Hong Kong region. The admixed Hawaiian population subsequently served as the source, through a bridgehead, for one introduction to the southeastern US. A separate introduction event from southcentral China subsequently occurred in Florida showing admixture with the first introduction. Overall, these findings further reinforce the pivotal role of bridgeheads in shaping species distributions in the Anthropocene and illustrate that the global distribution of C. formosanus has been shaped by multiple introductions out of China, which may have prevented and possibly reversed the loss of genetic diversity within its invasive range.

Profiling the Functional Diversity of Termite Mound Soil Bacteria as Revealed by Shotgun Sequencing.

Profiling the metabolic processes performed by bacteria is vital both for understanding and for manipulating ecosystems for industrial or research purposes. In this study we aim to assess the bacterial functional diversity in termite mound soils with the assumption that significant differences will be observed in the functional diversity of bacteria between the termite mound soils and their surrounding soils and that each environment has a distinguishing metabolic profile. Here, metagenomic DNA extracted from termite mound soils and their corresponding surrounding soils, which are 10 m apart, were sequenced using a shotgun sequencing approach. Our results revealed that the relative abundances of 16 functional categories differed significantly between both habitats. The α diversity analysis indicated no significant difference in bacterial functional categories within the habitats while the ß diversity showed that the bacterial functional categories varied significantly between the termite mound soils and the surrounding soil samples. The variations in soil physical and chemical properties existing between the two environments were held accountable for the differences in bacterial functional structure. With the high relative abundance of functional categories with unknown function reported in this study, this could signify the likelihood of getting novel genes from termite mound soils, which are needed for research and commercial applications.

Fine-tuned intruder discrimination favors ant parasitoidism.

A diversity of arthropods (myrmecophiles) thrives within ant nests, many of them unmolested though some, such as the specialized Eucharitidae parasitoids, may cause direct damage to their hosts. Ants are known to discriminate between nestmates and non-nestmates, but whether they recognize the strength of a threat and their capacity to adjust their behavior accordingly have not been fully explored. We aimed to determine whether Ectatomma tuberculatum ants exhibited specific behavioral responses to potential or actual intruders posing different threats to the host colony and to contribute to an understanding of complex ant-eucharitid interactions. Behavioral responses differed significantly according to intruder type. Ants evicted intruders that represented a threat to the colony's health (dead ants) or were not suitable as prey items (filter paper, eucharitid parasitoid wasps, non myrmecophilous adult weevils), but killed potential prey (weevil larvae, termites). The timing of detection was in accordance with the nature and size of the intruder: corpses (a potential source of contamination) were detected faster than any other intruder and transported to the refuse piles within 15 min. The structure and complexity of behavioral sequences differed among those intruders that were discarded. Workers not only recognized and discriminated between several distinct intruders but also adjusted their behavior to the type of intruder encountered. Our results confirm the previously documented recognition capabilities of E. tuberculatum workers and reveal a very fine-tuned intruder discrimination response. Colony-level prophylactic and hygienic behavioral responses through effective removal of inedible intruders appears to be the most general and flexible form of defense in ants against a diverse array of intruders. However, this generalized response to both potentially lethal and harmless intruders might have driven the evolution of ant-eucharitid interactions, opening a window for parasitoid attack and allowing adult parasitoid wasps to quickly leave the natal nest unharmed.

Comparison of the gut microbiota froms oldier and worker castes of the termite Reticulitermes grassei

The bacterial microbiota from the whole gut of soldier and worker castes of the termite Reticulitermes grassei was isolated and studied. In addition, the 16S rDNA bacterial genes from gut DNA were PCR-amplified using Bacteria-selective primers, and the 16S rDNA amplicons subsequently cloned into Escherichia coli. Sequences of the cloned inserts were then used to determine closest relatives by comparison with published sequences and with sequences from our previous work. The clones were found to be affiliated with the phyla Spirochaetes, Proteobacteria, Firmicutes, Bacteroidetes, Actinobacteria, Synergistetes, Verrucomicrobia, and candidate phyla Termite Group 1 (TG1) and Termite Group 2 (TG2). No significant differences were observed with respect to the relative bacterial abundances between soldier and worker phylotypes. The phylotypes obtained in this study were compared with reported sequences from other termites, especially those of phylotypes related to Spirochaetes, Wolbachia (an Alphaproteobacteria), Actinobacteria, and TG1. Many of the clone phylotypes detected in soldiers grouped with those of workers. Moreover, clones CRgS91 (soldiers) and CRgW68 (workers), both affiliated with ‘Endomicrobia’, were the same phylotype. Soldiers and workers also seemed to have similar relative protist abundances. Heterotrophic, poly-β-hydroxyalkanoate-accumulating bacteria were isolated from the gut of soldiers and shown to be affiliated with Actinobacteria and Gammaproteobacteria. We noted that Wolbachia was detected in soldiers but not in workers. Overall, the maintenance by soldiers and workers of comparable axial and radial redox gradients in the gut is consistent with the similarities in the prokaryotes and protists comprising their microbiota (AU)

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Susceptibility of Nasutitermes ehrhardti (Isoptera: Termitidae) to Bacillus thuringiensis subspecies

The effects of Bacillus thuringiensis (Bt) Berliner on the termite Nasutitermes ehrhardti (Isoptera, Termitidae) were evaluated under laboratory conditions. From 55 Bt subspecies assayed in vivo under controlled conditions seven were found to be pathogenic in the subspecies yunnanensis, huazhongiensis, brasiliensis, colmeri and kurstaki (less than 72 percent of mortality), particularly sooncheon and roskildiensis (100 percent mortality at the seventh day after the bacteria application). The LC50 for subspecie sooncheon corresponded to 47x10(8),()66.2x10(6) and 5.1x10(5) cells/ml, at the third, fifth and seventh day, respectively. For the subspecie roskildiensis the LC50 corresponded to 30.8x10(5), 48.4x10(6) and 16.8x10(4) cells/ml, at the third, fifth and seventh day, respectively. The results show that the two most pathogenic subspecies effectively may be studied with regard to control the termite N. ehrhardti