Global population genetic structure and demographic trajectories of the black soldier fly, Hermetia illucens

Background The black soldier fly (Hermetia illucens) is the most promising insect candidate for nutrient-recycling through bioconversion of organic waste into biomass, thereby improving sustainability of protein supplies for animal feed and facilitating transition to a circular economy. Contrary to conventional livestock, genetic resources of farmed insects remain poorly characterised. We present the first comprehensive population genetic characterisation of H. illucens. Based on 15 novel microsatellite markers, we genotyped and analysed 2862 individuals from 150 wild and captive populations originating from 57 countries on seven subcontinents. Results We identified 16 well-distinguished genetic clusters indicating substantial global population structure. The data revealed genetic hotspots in central South America and successive northwards range expansions within the indigenous ranges of the Americas. Colonisations and naturalisations of largely unique genetic profiles occurred on all non-native continents, either preceded by demographically independent founder events from various single sources or involving admixture scenarios. A decisive primarily admixed Polynesian bridgehead population serially colonised the entire Australasian region and its secondarily admixed descendants successively mediated invasions into Africa and Europe. Conversely, captive populations from several continents traced back to a single North American origin and exhibit considerably reduced genetic diversity, although some farmed strains carry distinct genetic signatures. We highlight genetic footprints characteristic of progressing domestication due to increasing socio-economic importance of H. illucens, and ongoing introgression between domesticated strains globally traded for large-scale farming and wild populations in some regions. Conclusions We document the dynamic population genetic history of a cosmopolitan dipteran of South American origin shaped by striking geographic patterns. These reflect both ancient dispersal routes, and stochastic and heterogeneous anthropogenic introductions during the last century leading to pronounced diversification of worldwide structure of H. illucens. Upon the recent advent of its agronomic commercialisation, however, current human-mediated translocations of the black soldier fly largely involve genetically highly uniform domesticated strains, which meanwhile threaten the genetic integrity of differentiated unique local resources through introgression. Our in-depth reconstruction of the contemporary and historical demographic trajectories of H. illucens emphasises benchmarking potential for applied future research on this emerging model of the prospering insect-livestock sector.Additional co-authors: Santos Rojo, Chrysantus M. Tanga, Rudolf Meier, Clint Rhode, Christine J. Picard, Chris D. Jiggins, Florian Leiber, Jeffery K. Tomberlin, Martin Hasselmann, Wolf U. Blanckenhorn, Martin Kapun & Christoph Sandroc

Global population genetic structure and demographic trajectories of the black soldier fly, Hermetia illucens

Background The black soldier fly (Hermetia illucens) is the most promising insect candidate for nutrient-recycling through bioconversion of organic waste into biomass, thereby improving sustainability of protein supplies for animal feed and facilitating transition to a circular economy. Contrary to conventional livestock, genetic resources of farmed insects remain poorly characterised. We present the first comprehensive population genetic characterisation of H. illucens. Based on 15 novel microsatellite markers, we genotyped and analysed 2862 individuals from 150 wild and captive populations originating from 57 countries on seven subcontinents. Results We identified 16 well-distinguished genetic clusters indicating substantial global population structure. The data revealed genetic hotspots in central South America and successive northwards range expansions within the indigenous ranges of the Americas. Colonisations and naturalisations of largely unique genetic profiles occurred on all non-native continents, either preceded by demographically independent founder events from various single sources or involving admixture scenarios. A decisive primarily admixed Polynesian bridgehead population serially colonised the entire Australasian region and its secondarily admixed descendants successively mediated invasions into Africa and Europe. Conversely, captive populations from several continents traced back to a single North American origin and exhibit considerably reduced genetic diversity, although some farmed strains carry distinct genetic signatures. We highlight genetic footprints characteristic of progressing domestication due to increasing socio-economic importance of H. illucens, and ongoing introgression between domesticated strains globally traded for large-scale farming and wild populations in some regions. Conclusions We document the dynamic population genetic history of a cosmopolitan dipteran of South American origin shaped by striking geographic patterns. These reflect both ancient dispersal routes, and stochastic and heterogeneous anthropogenic introductions during the last century leading to pronounced diversification of worldwide structure of H. illucens. Upon the recent advent of its agronomic commercialisation, however, current human-mediated translocations of the black soldier fly largely involve genetically highly uniform domesticated strains, which meanwhile threaten the genetic integrity of differentiated unique local resources through introgression. Our in-depth reconstruction of the contemporary and historical demographic trajectories of H. illucens emphasises benchmarking potential for applied future research on this emerging model of the prospering insect-livestock sector.Peer reviewe

A comparative phenetic and cladistic analysis of the genus Holcaspis Chaudoir (Coleoptera: Carabidae)

The systematics of the endemic New Zealand carabid genus Holcaspis are investigated, using phenetic and cladistic methods, to construct phenetic and phylogenetic relationships. Three different character data sets: morphological, allozyme and random amplified polymorphic DNA (RAPD) based on the polymerase chain reaction (PCR), are used to estimate the relationships. Cladistic and morphometric analyses are undertaken on adult morphological characters. Twenty six external morphological characters, including male and female genitalia, are used for cladistic analysis. The results from the cladistic analysis are strongly congruent with previous publications. The morphometric analysis uses multivariate discriminant functions, with 18 morphometric variables, to derive a phenogram by clustering from Mahalanobis distances (D²) of the discrimination analysis using the unweighted pair-group method with arithmetical averages (UPGMA). In contrast to the cladistic analysis, the phonetic clustering results in a less useful estimation of affinities of the genus. However, this analysis reveals a method with a relatively high probability of assigning an individual to the correct species (70%-100%). Therefore morphometric analysis is shown to be useful for species identification. Allozyme data are derived by electrophoresis using a cellulose acetate medium. A total of 42 alleles of 13 presumptive loci from 10 enzyme systems are used for cladistic and phenetic analysis of 13 Holcaspis species. A phenogram is generated by UPGMA clustering using a genetic distance matrix. Cladograms are constructed using both independent alleles and loci as characters. The cladograms from both allele and locus data are highly congruent with the phenogram derived from the genetic similarity matrix data. Intraspecific allozyme variation is also investigated with a limited number of populations and a relatively confined range of sample sites. A high degree of heterozygosity is revealed in H. oedicnema. The mean genetic similarity among the Holcaspis species is I= 0.382±0.142 and the mean genetic distance is D= l.055±0.143. Molecular data are used in the intraspecific variation study and to estmate species relationships of Holcaspis. Optimal RAPD-PCR conditions such as primer concentration, magnesium chloride concentration and RAPD-PCR programme, are established for reproducible and informative amplifying of banding patterns of Holcaspis species. A total of 271 band positions are scored for all individuals studied and are subjected to both cladistic and phenetic analysis to estimate the species relationships. Phenograms using UPGMA are generated from both simple matching similarity coefficients and Jaccard's similarity coefficients. The resulting two phenograms are identical. Principal coordinate analysis is also used to demonstrate the relationships among species. The results are congruent with the phenograms. However, the pattern of species relationships is indistinct. The cladogram generated from cladistic analysis shows relatively high congruence with the phenogram. In addition, the results from RAPD-PCR are much more congruent with the results from allozyme data than with the morphological data. The RAPD-PCR technique is, therefore, promising as a new tool for estimating phylogenetic relationships. In addition, the results show that the RAPD-PCR technique is a constructive, quick method for species grouping. From both RAPD-PCR and allozyme data, H. oedicnema shows extreme intraspecific variation that suggests that H. oedicnema is a species complex. To assess the best fit of phylogenetic relationships of the Holcaspis species, three character data sets: morphological, allozyme, and RAPD-PCR, are tested for congruence using both character congruence and taxonomic congruence method. The result indicates that the character congruence method of all character data sets combined produced a more informative result than the taxonomic congruence method. This study confirms the previous indication that H. punctigera and H. mordax are closely related both morphologically and genetically. The study suggests that H. ovatella is most genetically distinct from the rest of the Holcaspis species and that H. oedicnema is a genetically diverse species

Evaluation of colour traps to monitor insect vectors of sugarcane white leaf phytoplasma

Abstract The present study was conducted to evaluate the attractiveness of various colour sticky traps and light tarps at sugarcane field in Phandon village, Kumpawapi district, Udon Thani Province, Northeast region of Thailand for the insect vectors of sugarcane white leaf phytoplasma, the leafhoppers Matsumuratettix hiroglyphicus (Matsumura) and Yamatotettix flavovittatus Matsumura to. In sticky traps experiment, yellow, blue, white, green, orange and colorless (control) were used. A higher number of the putative vectors, Matsumuratettix hiroglyphicus and Yamatotettix flavovittatus were trapped on blue and yellow as compared to white, orange, green and colorless (control) sticky traps. In light traps experiment, yellow, green, black light-blue and black color light sources were used. With regard to treatment colour light traps with black light-blue trapped significantly higher numbers of both leafhoppers followed by black, green and yellow traps. The light traps were found significantly more attractive to both species of insect vectors compared to sticky traps, as lower number of insect vectors were trapped on sticky traps. In conclusion, a trap with black light-blue colour was the best attractive equipment for monitoring the of insect vectors of sugarcane white leaf phytoplasma in sugarcane fields

Different effects of earthworms and ants on soil properties of paddy fields in North-East Thailand

International audienceAs soil engineers, earthworms and ants play major roles in soil functioning, especially in modifying soil physical and chemical properties. This study was con- ducted in a very constraining environment, i.e., paddy fields which have anoxic conditions (approximately four months per year), and which are affected by soil salinisa- tion during the dry period (approximately eight months per year). This study points out that despite those very adverse conditions, soil invertebrates must be taken into account in the dynamic of soil organic and mineral properties in paddy fields. The effects of one earthworm species, Glyphodrillus sp., and an ant species, Epelysidris sp., on soil physical and chemical properties were determined through elemental soil physical and chemical properties (texture, pH, con- ductivity, C and N contents) and near infrared reflectance spectroscopy (NIRS) in order to evaluate their ability to influence soil organic matter quality. PCA processed with NIRS data clearly showed that biogenic structures (ant sheetings and earthworm casts) were separated from the control surrounding soil. Earthworms and ants affected differently soil properties. Glyphodrillus sp. increased the SOM content and decreased the pH on the surface of the soil. These effects were attributed to an increase in fine particle content (clay). Conversely, Epelysidris sp. only increased the content of coarse particles (sand) and did not influence either soil pH or SOM content. Soil conductivity was found to be very variable but was not significantly affected by soil invertebrates. These results show the potential of soil macro-fauna to create heterogeneity at small spatial scale and to modify the quality of surface soils even under adverse conditions like saline paddy fields

Indoor resting behavior of Aedes aegypti (Diptera: Culicidae) in northeastern Thailand

BACKGROUND: Aedes aegypti is a vector of several arboviruses, notably dengue virus (DENV), which causes dengue fever and is often found resting indoors. Culex spp. are largely nuisance mosquitoes but can include species that are vectors of zoonotic pathogens. Vector control is currently the main method to control dengue outbreaks. Indoor residual spraying can be part of an effective vector control strategy but requires an understanding of the resting behavior. Here we focus on the indoor-resting behavior of Ae. aegypti and Culex spp. in northeastern Thailand. METHODS: Mosquitoes were collected in 240 houses in rural and urban settings from May to August 2019 at two collection times (morning/afternoon), in four room types (bedroom, bathroom, living room and kitchen) in each house and at three wall heights (< 0.75 m, 0.75-1.5 m, > 1.5 m) using a battery-driven aspirator and sticky traps. Household characteristics were ascertained. Mosquitoes were identified as Ae. aegypti, Aedes albopictus and Culex spp. Dengue virus was detected in Ae. aegypti. Association analyses between urban/rural and within-house location (wall height, room), household variables, geckos and mosquito abundance were performed. RESULTS: A total of 2874 mosquitoes were collected using aspirators and 1830 using sticky traps. Aedes aegypti and Culex spp. accounted for 44.78% and 53.17% of the specimens, respectively. Only 2.05% were Ae. albopictus. Aedes aegypti and Culex spp. rested most abundantly at intermediate and low heights in bedrooms or bathrooms (96.6% and 85.2% for each taxon of the total, respectively). Clothes hanging at intermediate heights were associated with higher mean numbers of Ae. aegypti in rural settings (0.81 [SEM: 0.08] vs. low: 0.61 [0.08] and high: 0.32 [0.09]). Use of larval control was associated with lower numbers of Ae. aegypti (yes: 0.61 [0.08]; no: 0.70 [0.07]). All DENV-positive Ae. aegypti (1.7%, 5 of 422) were collected in the rural areas and included specimens with single, double and even triple serotype infections. CONCLUSIONS: Knowledge of the indoor resting behavior of adult mosquitoes and associated environmental factors can guide the choice of the most appropriate and effective vector control method. Our work suggests that vector control using targeted indoor residual spraying and/or potentially spatial repellents focusing on walls at heights lower than 1.5 m in bedrooms and bathrooms could be part of an integrated effective strategy for dengue vector control

Bacterial challenge-associated metabolic phenotypes in Hermetia illucens defining nutritional and functional benefits

Black soldier fly (BSF, Hermetia illucens) is popular for its applications in animal feed, waste management and antimicrobial peptide source. The major advantages of BSF larva include their robust immune system and high nutritional content that can be further developed into more potential agricultural and medical applications. Several strategies are now being developed to exploit their fullest capabilities and one of these is the immunity modulation using bacterial challenges. The mechanism underlying metabolic responses of BSF to different bacteria has, however, remained unclear. In the current study, entometabolomics was employed to investigate the metabolic phenoconversion in response to either Escherichia coli, Staphylococcus aureus, or combined challenges in BSF larva. We have, thus far, characterized 37 metabolites in BSF larva challenged with different bacteria with the major biochemical groups consisting of amino acids, organic acids, and sugars. The distinct defense mechanism-specific metabolic phenotypes were clearly observed. The combined challenge contributed to the most significant metabolic phenoconversion in BSF larva with the dominant metabolic phenotypes induced by S. aureus. Our study suggested that the accumulation of energy-related metabolites provided by amino acid catabolism is the principal metabolic pathway regulating the defense mechanism. Therefore, combined challenge is strongly recommended for raising BSF immunity as it remarkably triggered amino acid metabolisms including arginine and proline metabolism and alanine, aspartate and glutamate metabolism along with purine metabolism and pyruvate metabolism that potentially result in the production of various nutritional and functional metabolites