Acetylcholinesterase is the primary target of organophosphates (OPs) and carbamates in insects. As gene mutation has been verified as an important mechanism of insecticide resistance in insects, in this study, we investigated the status of OPs resistance and the polymorphism of ace gene (that encodes acetylcholinesterase) in housefly (Musca domestica L) field populations in Guizhou Province, China. Bioassays showed that the houseflies had 142.16–303.54-fold resistance to dichlorvos (DDVP) and 122.13–363.98-fold resistance to temephos. Molecular analysis revealed resistance-causing mutations of ace gene at loci of 260, 342 and 407 in the housefly populations, with a total frequency of 55%, 100% and 94%, respectively. In addition, 11 combinations of ace mutation were observed across the detected populations. The most frequently detected combination was L/V+A/V+Y, followed by L+A+Y and L/V+A+Y. No significant relationship was found between single mutation/combination mutations and DDVP resistance. These results indicate that the OPs resistance is prevalent among the housefly populations in Guizhou Province, with a similar pattern of allele mutation of ace across China. The target resistance can not fully account for the resistance of houseflies to OPs in Guizhou.

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Hybridization between species is likely to be associated with a new ecological impact. However, in termites, reports of hybridization mostly focus on hybrid zones caused by species invasion or the development of initial-stage colonies. In this study, we combined microsatellite genotyping with mitochondrial DNA sequencing to investigate the hybridization and adaptive introgression between two sympatric, long-differentiated related termite species, Reticulitermes flaviceps and R. chinensis, in nature. Similar levels of mitochondrial and nuclear genetic diversity were found in R. flaviceps and R. chinensis. Asymmetric interspecific genetic differentiation was observed between mitochondrial and nuclear genes, with high genetic divergence found in mitochondrial DNA but low genetic divergence in nuclear genes. Our results indicated a lack of mitochondrial gene exchange in R. flaviceps and R. chinensis but unconstrained nuclear introgression between them. This asymmetric genetic differentiation between nuclear and cytoplasmic material strongly suggests that there is interspecific hybridization between R. flaviceps and R. chinensis in nature, which provides new insight into the dynamics of hybridization and its potential consequences for speciation in termites.

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Background: Vector control has been a key strategy in malaria prevention and elimination for decades. However, insecticide resistance is becoming a serious threat to vector control. Anopheles sinensis is one of the important transmission vectors for malaria in Guizhou Province, China. However, little is known on insecticide resistance status and related mechanism. In this study, the diversity and frequency of the major insecticide resistance associated genes such as voltage-gated sodium channel (vgsc) and acetylcholinesterase-1 ( ace-1 ) genes that encoded the target proteins of Pyrethroids and OPs were investigated in field populations.Methods: Adult mosquitoes were collected from 12 sampling sites across Guizhou by lamp trapping. Female An. sinensis were identified by morphological and molecular identification. Genomic DNA was extracted to amplify vgsc and ace-1 gene fragments. PCR products were sequenced bi-directly. Mutations of vgsc gene at locus 1014 and that of ace-1 at locus 119 were analyzed using MEGA 7.1 software, and the frequencies of mutations were calculated respectively.Results: 5 kdr mutation alleles at the locus 1014 of vgsc gene as a result of three amino acid replacements ( namely 1014F/C/S) in 548 samples of 12 An. sinensis populations. The total frequency of kdr mutation alleles was 27.4%, of which the TTT/C (F) allele had a highest mutation frequency of 22.5%. The top three mutation genotypes were from XiShui, TongZhi and DeJiang populations collected in north Guizhou. There were three alleles at locus 119 in ace-1 gene with 49.47% of GGC/G, 0.17% of GGT/G and 50.36% of AGC/S. The 100% frequency of mutation genotypes (GS, SS) was found in CeHeng, LuoDian and SanDu populations gathered in southwest Guizhou.Conclusion: A diverse genetic mutations of vgsc and ace-1 genes are found in An. sinensis in Guizhou. There are a significant geographical heterogeneities of allele frequency among different populations in Guizhou. A high frequency of kdr mutation (>44 %) in north Guizhou. The 119S mutation of ace-1 gene is present at a high frequency in most An. sinensis populations in Guizhou, especially in the previously highly endemic malaria regions. These findings suggest continued monitoring of the genotypic diversity of insecticides resistance genes may assist to formulate a region-customized resistance management strategies.