Evaluation of identification methods for cryptic Bactrocera dorsalis (Diptera: Tephritidae) specimens: combining morphological and molecular techniques.

The potential for population genomics to elucidate invasion pathways of a species is limited by taxonomic identification issues. The Oriental fruit fly pest, Bactrocera dorsalis (Hendel) belongs to a complex in which several sympatric species are attracted to the same lure used in trapping and are morphologically cryptic and/or reported to hybridize. In this study, we evaluated the taxonomic ambiguity between B.

Evaluation of 96-well high-throughput DNA extraction methods for 16S rRNA gene metabarcoding.

Gaining meaningful insights into bacterial communities associated with animal hosts requires the provision of high-quality nucleic acids. Although many studies have compared DNA extraction methods for samples with low bacterial biomass (e.g.

Domestication provides durum wheat with protection from locust herbivory.

Lower plant resistance to herbivores following domestication has been suggested as the main cause for higher feeding damage in crops than in wild progenitors. While herbivore compensatory feeding has also been proposed as a possible mechanism for raised damage in crops with low nutritional quality, predictions regarding the effects of plant domestication on nutritional quality for herbivores remain unclear. In particular, data on primary metabolites, even major macronutrients, measured in the organs consumed by herbivores, are scarce.

Faeces' odours attract gregarious locust hoppers.

Collective motion is one of the most impressive common features of gregarious locusts: once formed, bands and swarms get moving for long distances. It was shown that visual perception of neighbours plays a key role in maintaining marching behaviour at a local scale. But at a larger scale, mechanisms underlying band cohesion are less understood.

Does Host Plant Drive Variation in Microbial Gut Communities in a Recently Shifted Pest?

Biotic interactions can modulate the responses of organisms to environmental stresses, including diet changes. Gut microbes have substantial effects on diverse ecological and evolutionary traits of their hosts, and microbial communities can be highly dynamic within and between individuals in space and time. Modulations of the gut microbiome composition and their potential role in the success of a species to maintain itself in a new environment have been poorly studied to date.

Additive genetic variance for traits least related to fitness increases with environmental stress in the desert locust, .

Under environmental stress, previously hidden additive genetic variation can be unmasked and exposed to selection. The amount of hidden variation is expected to be higher for life history traits, which strongly correlate to individual fitness, than for morphological traits, in which fitness effects are more ambiguous. However, no consensual pattern has been recovered yet, and this idea is still debated in the literature.

Integrative taxonomy confirms that Gregarina garnhami and G. acridiorum (Apicomplexa, Gregarinidae), parasites of Schistocerca gregaria and Locusta migratoria (Insecta, Orthoptera), are distinct species.

Orthoptera are infected by about 60 species of gregarines assigned to the genus Gregarina Dufour, 1828. Among these species, Gregarina garnhami Canning, 1956 from Schistocerca gregaria (Forsskål, 1775) was considered by Lipa et al. in 1996 to be synonymous with Gregarina acridiorum (Léger 1893), a parasite of several orthopteran species including Locusta migratoria (Linné, 1758).

A young age of subspecific divergence in the desert locust inferred by ABC random forest.

Dating population divergence within species from molecular data and relating such dating to climatic and biogeographic changes is not trivial. Yet it can help formulating evolutionary hypotheses regarding local adaptation and future responses to changing environments. Key issues include statistical selection of a demographic and historical scenario among a set of possible scenarios, and estimation of the parameter(s) of interest under the chosen scenario.

On the relative role of climate change and management in the current desert locust outbreak in East Africa.

While large-scale monitoring, early detection and control can greatly reduce desert locust invasions, global change is most likely to affect conditions that promote the transition from solitary to gregarious populations. Although climate change scenarios point to an increase in aridity and further desertification in vast areas of Africa, some regions that have been at the origin of past outbreaks are likely to see a reversed trend (i.e.

Deciphering host-parasitoid interactions and parasitism rates of crop pests using DNA metabarcoding.

An accurate estimation of parasitism rates and diversity of parasitoids of crop insect pests is a prerequisite for exploring processes leading to efficient natural biocontrol. Traditional methods such as rearing have been often limited by taxonomic identification, insect mortality and intensive work, but the advent of high-throughput sequencing (HTS) techniques, such as DNA metabarcoding, is increasingly seen as a reliable and powerful alternative approach. Little has been done to explore the benefits of such an approach for estimating parasitism rates and parasitoid diversity in an agricultural context.

Exploring the relationship between tychoparthenogenesis and inbreeding depression in the Desert Locust, .

Tychoparthenogenesis, a form of asexual reproduction in which a small proportion of unfertilized eggs can hatch spontaneously, could be an intermediate evolutionary link in the transition from sexual to parthenogenetic reproduction. The lower fitness of tychoparthenogenetic offspring could be due to either developmental constraints or to inbreeding depression in more homozygous individuals. We tested the hypothesis that in populations where inbreeding depression has been purged, tychoparthenogenesis may be less costly.

Climate-driven geographic distribution of the desert locust during recession periods: Subspecies' niche differentiation and relative risks under scenarios of climate change.

The desert locust is an agricultural pest that is able to switch from a harmless solitarious stage, during recession periods, to swarms of gregarious individuals that disperse long distances and affect areas from western Africa to India during outbreak periods. Large outbreaks have been recorded through centuries, and the Food and Agriculture Organization keeps a long-term, large-scale monitoring survey database in the area. However, there is also a much less known subspecies that occupies a limited area in Southern Africa.

Extra Molting and Selection on Nymphal Growth in the Desert Locust.

In insects, extra-molting has been viewed as a compensatory mechanism for nymphal growth that contributes to optimize body weight for successful reproduction. However, little is known on the capacity of extra-molting to evolve in natural populations, which limits our understanding of how selection acts on nymphal growth. We used a multi-generational pedigree, individual monitoring and quantitative genetics models to investigate the evolution of extra-molting and its impact on nymphal growth in a solitarious population of the desert locust, Schistocerca gregaria.

Evidence for high dispersal ability and mito-nuclear discordance in the small brown planthopper, Laodelphax striatellus.

Understanding dispersal ability in pest species is critical for both theoretical aspects of evolutionary and population biology and from a practical standpoint, such as implementing effective forecasting systems. The small brown planthopper (SBPH), Laodelphax striatellus (Fallén), is an economically important pest, but few data exist on its dispersal ability. Here, we used mitochondrial and nuclear markers to elucidate the population genetic structure of SBPH and of the parasitic bacterium Wolbachia throughout temperate and subtropical China.

Demographic processes shaping genetic variation of the solitarious phase of the desert locust.

Between plagues, the solitarious desert locust (Schistocerca gregaria) is generally thought to exist as small populations, which are particularly prone to extinction events in arid regions of Africa and Asia. Given the high genetic structuring observed in one geographical area (the Eritrean coast) by former authors, a metapopulation dynamics model involving repeated extinction and colonization events was favoured. In this study, we assessed the validity of a demographic scenario involving temporary populations of the solitarious phase of the desert locust by analysing large-scale population genetic data.

Microsatellite markers for the Chameleon grasshopper (Kosciuscola tristis) (Orthoptera: Acrididae), an Australian Alpine Specialist.

A set of polymorphic loci was characterised using an enrichment library for the Australian alpine specialist, the chameleon grasshopper (Kosciuscola tristis), an atypical grasshopper known for its remarkable temperature-controlled colour change. The number of alleles per locus ranged from three to 20 and observed heterozygosity from 0.16 to 0.

Mitochondrial genomes reveal the global phylogeography and dispersal routes of the migratory locust.

The migratory locust, Locusta migratoria, is the most widely distributed grasshopper species in the world. However, its global genetic structure and phylogeographic relationships have not been investigated. In this study, we explored the worldwide genetic structure and phylogeography of the locust populations based on the sequence information of 65 complete mitochondrial genomes and three mitochondrial genes of 263 individuals from 53 sampling sites.

Isolation and characterization of twelve polymorphic microsatellite Loci for the cocoa mirid bug Sahlbergella singularis.

Mirids are the primary pests affecting cocoa production in Africa, but no genetic studies have been conducted on these insects. Here we report the isolation and characterization of 12 polymorphic microsatellite loci for Sahlbergella singularis. A microsatellite-enriched genomic DNA library was developed and screened to identify marker loci.

Long microsatellites and unusually high levels of genetic diversity in the Orthoptera.

Much remains to be learned about the mutational processes governing the evolution of microsatellite repeat regions and the associated levels of genetic diversity observed at microsatellite markers across populations or species. An extensive survey of microsatellite variation in 210 insect species from six major orders revealed that within Orthopterans, which are characterized by giant genomes, levels of genetic diversity were ~20% higher and microsatellite repeat arrays were longer than in any other group. Because of the mutation dependence on repeat length, this result suggests a higher microsatellite loci mutation rate in the Orthoptera.

Taxa-specific heat shock proteins are over-expressed with crowding in the Australian plague locust.

Most heat shock proteins (Hsps) function as molecular chaperones that help organisms to cope with stress. Although the best empirical evidence is related to heat shock, there is evidence that Hsps and their encoding genes are involved in resistance to other ecologically relevant types of stresses such as those imposed by high population density. We quantified density-dependent gene expression of large (i.

Evaluation of potential reference genes for reverse transcription-qPCR studies of physiological responses in Drosophila melanogaster.

Drosophila melanogaster is one of the most important genetic models and techniques such as reverse transcription quantitative real-time PCR (RT-qPCR) are being employed extensively for deciphering the genetics basis of physiological functions. In RT-qPCR, the expression levels of target genes are estimated on the basis of endogenous controls. The purpose of these reference genes is to control for variations in RNA quantity and quality.

Challenges to assessing connectivity between massive populations of the Australian plague locust.

Linking demographic and genetic dispersal measures is of fundamental importance for movement ecology and evolution. However, such integration can be difficult, particularly for highly fecund species that are often the target of management decisions guided by an understanding of population movement. Here, we present an example of how the influence of large population sizes can preclude genetic approaches from assessing demographic population structuring, even at a continental scale.

Assessment and validation of a suite of reverse transcription-quantitative PCR reference genes for analyses of density-dependent behavioural plasticity in the Australian plague locust.

Background: The Australian plague locust, Chortoicetes terminifera, is among the most promising species to unravel the suites of genes underling the density-dependent shift from shy and cryptic solitarious behaviour to the highly active and aggregating gregarious behaviour that is characteristic of locusts. This is because it lacks many of the major phenotypic changes in colour and morphology that accompany phase change in other locust species. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) is the most sensitive method available for determining changes in gene expression.

Outbreaks, gene flow and effective population size in the migratory locust, Locusta migratoria: a regional-scale comparative survey.

The potential effect of population outbreaks on within and between genetic variation of populations in pest species has rarely been assessed. In this study, we compare patterns of genetic variation in different sets of historically frequently outbreaking and rarely outbreaking populations of an agricultural pest of major importance, the migratory locust, Locusta migratoria. We analyse genetic variation within and between 24 populations at 14 microsatellites in Western Europe, where only ancient and low-intensity outbreaks have been reported (non-outbreaking populations), and in Madagascar and Northern China, where frequent and intense outbreak events have been recorded over the last century (outbreaking populations).