Wood feeding and social living: Draft genome of the subterranean termite Reticulitermes lucifugus (Blattodea; Termitoidae)

Insecticide resistance in social insects: assumptions, realities, and possibilities

Insecticide resistance is an evolved ability to survive insecticide exposure. Compared with nonsocial insects, eusocial insects have lower numbers of documented cases of resistance. Eusocial insects include beneficial and pest species that can be incidentally or purposely targeted with insecticides. The central goal of this review is to explore factors that either limit resistance or the ability to detect it in eusocial insects. We surveyed the literature and found that resistance has been documented in bees, but in other pest groups such as ants and termites, the evidence is more sparse. We suggest the path forward for better understanding eusocial resistance should include more tractable experimental models, comprehensive geographic sampling, and targeted testing of the impacts of social, symbiont, genetic, and ecological factors.

Molecular phylogeny and morphology reveal two new entomopathogenic species of Ophiocordyceps (Ophiocordycipitaceae, Hypocreales) parasitic on termites from China

Two new termite-pathogenic species, Ophiocordycepsglobiperitheciata and O.longistipes, are described from Yunnan Province, China. Six-locus (ITS, nrSSU, nrLSU, tef-1α, rpb1 and rpb2) phylogenetic analyses in combination with morphological observations were employed to characterize these two species. Phylogenetically, O.globiperitheciata is most closely related to Hirsutellacryptosclerotium and O.communis, whereas O.longistipes shares a sister relationship with O.fusiformis. However, O.globiperitheciata differs from H.cryptosclerotium by parasitizing Blattodea and producing clavate, unbifurcated stromata. Ophiocordycepsglobiperitheciata is distinguished from O.communis by multiple stromata, shorter asci and ascospores. Ophiocordycepslongistipes differs from O.fusiformis in producing larger stromata, perithecia, asci and ascospores, as well as smaller citriform or oval conidia. Morphological descriptions of the two new species and a dichotomous key to the 19 termite-pathogenic Ophiocordyceps species are presented.

Candidate target genes of the male-specific expressed Doublesex in the termite Reticulitermes speratus

Eusocial insects such as termites, ants, bees, and wasps exhibit a reproductive division of labor. The developmental regulation of reproductive organ (ovaries and testes) is crucial for distinguishing between reproductive and sterile castes. The development of reproductive organ in insects is regulated by sex-determination pathways. The sex determination gene Doublesex (Dsx), encoding transcription factors, plays an important role in this pathway. Therefore, clarifying the function of Dsx in the developmental regulation of sexual traits is important to understand the social evolution of eusocial insects. However, no studies have reported the function of Dsx in hemimetabolous eusocial group termites. In this study, we searched for binding sites and candidate target genes of Dsx in species with available genome information as the first step in clarifying the function of Dsx in termites. First, we focused on the Reticulitermes speratus genome and identified 101 candidate target genes of Dsx. Using a similar method, we obtained 112, 39, and 76 candidate Dsx target genes in Reticulitermes lucifugus, Coptotermes formosanus, and Macrotermes natalensis, respectively. Second, we compared the candidate Dsx target genes between species and identified 37 common genes between R. speratus and R. lucifugus. These included several genes probably involved in spermatogenesis and longevity. However, only a few common target genes were identified between R. speratus and the other two species. Finally, Dsx dsRNA injection resulted in the differential expression of several target genes, including piwi-like protein and B-box type zinc finger protein ncl-1 in R. speratus. These results provide valuable resource data for future functional analyses of Dsx in termites.

Genomic signatures of eusocial evolution in insects

The genomes of eusocial insects allow the production and regulation of highly distinct phenotypes, largely independent of genotype. Although rare, eusociality has evolved convergently in at least three insect orders (Hymenoptera, Blattodea and Coleoptera). Despite such disparate origins, eusocial phenotypes show remarkable similarity, exhibiting long-lived reproductives and short-lived sterile workers and soldiers. In this article, we review current knowledge on genomic signatures of eusocial evolution. We confirm that especially an increased regulatory complexity and the adaptive evolution of chemical communication are common to several origins of eusociality. Furthermore, colony life itself can shape genomes of divergent taxa in a similar manner. Future research should be geared towards generating more high-quality genomic resources, especially in hitherto understudied clades, such as ambrosia beetles and termites. The application of more sophisticated tools such as machine learning techniques may allow the detection of more subtle convergent genomic footprints of eusociality.