Diversity and dynamics of microbial communities in brown planthopper at different developmental stages revealed by high-throughput amplicon sequencing.

The microbiome associated with brown planthopper (BPH) plays an important role in mediating host health and fitness. Characterization of the microbial community and its structure is prerequisite for understanding the intricate symbiotic relationships between microbes and host insect. Here, we investigated the bacterial and fungal communities of BPH at different developmental stages using high-throughput amplicon sequencing. Our results revealed that both the bacterial and fungal communities were diverse and dynamic during BPH development. The bacterial communities were generally richer than fungi in each developmental stage. At 97% similarly, 19 phyla and 278 genera of bacteria were annotated, while five fungal phyla comprising 80 genera were assigned. The highest species richness for the bacterial communities was detected in the nymphal stage. The taxonomic diversity of the fungal communities in female adults was generally at a relatively higher level when compared to other developmental stages. The most dominant phylum of bacteria and fungi at each developmental stage all belonged to Proteobacteria and Ascomycota, respectively. A significantly lower abundance of bacterial genus Acinetobacter was recorded in the egg stage when compared to other developmental stages, while the dominant fungal genus Wallemia was more abundant in the nymph and adult stages than in the egg stage. Additionally, the microbial composition differed between male and female adults, suggesting that the microbial communities in BPH were gender-dependent. Overall, our study enriches our knowledge on the microbial communities associated with BPH and will provide clues to develop potential biocontrol techniques against this rice pest.

DNA barcoding evaluation and implications for phylogenetic relationships in ladybird beetles (Coleoptera: Coccinellidae).

Ladybird beetles (Coleoptera: Coccinellidae), with broad morphological diversity, wide geographic distribution and substantial agricultural significance, are a challenging group for taxonomists and phylogenetics. As a promising tool to identify and discover new species, DNA barcoding might offer significant potential for identification, taxonomy and phylogeny of ladybird beetles. In the present study, a total of 1364 COI (cytochrome C oxidase subunit I) sequences representing 128 species from 52 genera of ladybird beetles were screened for barcoding evaluation and phylogenetic analysis. Our results from the barcoding analysis revealed that COI displays a similar level of species identification efficiency (nearly 90%) either based on Kimura two-parameter (K2P) distances calculation or on simplified neighbour-joining (NJ) tree construction. The phylogenetic relationships within the family Coccinellidae was analyzed by Bayesian-inference (BI) method. The phylogenetic results confirmed the monophyly of the subfamilies Microweisinae and Coccinellinae sensu Slipinski (2007), and suggested that the subfamilies Coccidulinae, Chilocorinae and Scymninae are paraphyletic. However, the phylogenetic relationships among different subfamilies are not clearly defined and thus remain to be thoroughly studied. Overall, our study confirmed the usefulness of DNA barcoding for coccinellid species identification and phylogenetic inference.

Assessing the effectiveness of mitochondrial COI and 16S rRNA genes for DNA barcoding of farmland spiders in China.

DNA barcoding has been widely used to identify and discover new species in a wide range of taxa. In order to assess the effectiveness of COI (cytochrome C oxidase subunit I) and 16S (16S ribosomal RNA) in the discrimination of spiders, we have generated 289 barcodes for a total of 56 farmland spider species from 14 different families for the first time in China. Our results reveal that the standard barcoding marker COI can be used to distinguish the farmland spiders both in species and family level by NJ tree-based method, despite the absence of a barcode gap between the intra- and inter-specific genetic divergences. 16S has a lower species identification success as compared with COI. However, almost 98% of the species can be correctly distinguished for both COI and 16S when a threshold of 3% nucleotide divergence was used for species discrimination. Our study significantly improves the barcode reference sequence library for Chinese farmland spiders, and will be very useful in pest management and eco-environmental monitoring and protection.