Genetic Variation in the Feeding Behavior of Isofemale Lines of Nesidiocoris tenuis

Zoophytophagous predators provide biocontrol services in various major crops of modern horticulture due to the combination of its predatory capacity and the induction of plant defenses derived from its phytophagy. However, under certain conditions of prey scarcity, these natural enemies can inflict plant damage. Exploitation of genetic variation and subsequent selective breeding on foraging traits is a potential alternative to overcome this inconvenience. In this study, we quantified the genetic variation of phytophagy and zoophagy of Nesidiocoristenuis (Reuter) (Hemiptera: Miridae), a zoophytophagous predator widely used in tomato crops to suppress key pests. We compared nine isofemale lines on their capacity to produce necrotic rings and wilting on tomato plants as a proxy for phytophagy, as well as their efficacy to prey on Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) eggs, as a proxy for zoophagy. Differences between isofemale lines in phytophagy and zoophagy indicated a genetic basis. Variation found in the zoophagy levels was larger than that in phytophagy levels. Our results showed that there is a genetic basis for the variation observed in the feeding behavior of isofemale lines of N.tenuis, highlighting the potential importance of selective breeding for such traits of biocontrol interest.

Paternally Inherited P-Element Copy Number Affects the Magnitude of Hybrid Dysgenesis in Drosophila simulans and D. melanogaster

Transposable elements (TEs) are repetitive regions of DNA that are able to self-replicate and reinsert themselves throughout host genomes. Since the discovery of TEs, a prevalent question has been whether increasing TE copy number has an effect on the fitness of their hosts. P-elements (PEs) in Drosophila are a well-studied TE that has strong phenotypic effects. When a female without PEs (M) is crossed to a male with them (P), the resulting females are often sterile, a phenomenon called hybrid dysgenesis (HD). Here, we used short- and long-read sequencing to infer the number of PEs in the genomes of dozens of isofemale lines from two Drosophila species and measured whether the magnitude of HD was correlated with the number of PEs in the paternal genome. Consistent with previous reports, we find evidence for a positive correlation between the paternal PE copy number and the magnitude of HD in progeny from ♀M × ♂ P crosses for both species. Other crosses are not affected by the number of PE copies. We also find that the correlation between the strength of HD and PE copy number differs between species, which suggests that there are genetic differences that might make some genomes more resilient to the potentially deleterious effects of TEs. Our results suggest that PE copy number interacts with other factors in the genome and the environment to cause HD and that the importance of these interactions is species specific.

Identifying genomic markers associated with female re-mating rate in Drosophila pseudoobscura by replicated bulk segregant analysis

ABSTRACTIdentifying loci associated with a phenotype is a critical step in many evolutionary studies. Most methods require large sample sizes or breeding designs that can be prohibitively difficult. Here we apply a rarely used approach to identify SNP loci associated with a complex phenotype. We mate siblings from isofemale lines isolate genotypes from three wild populations. After phenotyping we perform whole genome sequencing of isofemale lines from the extremes of the phenotypic distribution of each population and identify SNPs that are consistently fixed for alternative alleles across line pairs. The focal phenotype is female remating rate in the fly Drosophila pseudoobscura, defined as the willingness of a female to mate with a second male after her first mating. This is an integral part of mating system evolution, sexual selection and sexual conflict, and is a quantitative polygenic trait.About 200 SNPs are consistently fixed for alternate alleles in the three pairs of isofemale lines. We use different simulation approaches to explore how many SNPs would be expected to be fixed. We find the surprising result that we uncover fewer observed fixed SNPs than are expected by either simulation approach. We also complete functional analyses of these SNPs. Many lie near genes or regulatory regions known to be involved in Drosophila courtship and mating behaviours, and some have previously been associated with re-mating rates in Genome-Wide Association Studies. Given the small sample size, these results should be treated with caution. Nevertheless, this study suggests that even from a relatively small number of isofemale lines established from wild populations, it is possible to identify candidate loci potentially associated with a complex quantitative trait. However, further work is required to understand modelling the expected distribution of differences.

Genetic variation and phenotypic plasticity in circadian rhythms in an armed beetle, Gnatocerus cornutus (Tenebrionidae)

Circadian rhythms, their free-running periods and the power of the rhythms are often used as indicators of biological clocks, and there is evidence that the free-running periods of circadian rhythms are not affected by environmental factors, such as temperature. However, there are few studies of environmental effects on the power of the rhythms, and it is not clear whether temperature compensation is universal. Additionally, genetic variation and phenotypic plasticity in biological clocks are important for understanding the evolution of biological rhythms, but genetic and plastic effects are rarely investigated. Here, we used 18 isofemale lines (genotypes) of Gnatocerus cornutus to assess rhythms of locomotor activity, while also testing for temperature effects. We found that total activity and the power of the circadian rhythm were affected by interactions between sex and genotype or between sex, genotype and temperature. The males tended to be more active and showed greater increases in activity, but this effect varied across both genotypes and temperatures. The period of activity varied only by genotype and was thus independent of temperature. The complicated genotype–sex–environment interactions we recorded stress the importance of investigating circadian activity in more integrated ways.

The relationship of Wolbachia infection and different phenotypes in the Drosophila melanogaster natural populations from radioactively polluted and clear areas in Ukraine

Aim. The study was performed to investigate the relationship between Wolbachia infection and phenotypes that distinct from wild-type of Drosophila melanogaster from different localities in Ukraine including those from Chornobyl Exclusion Zone during 2013–2014. Methods. We have established isofemale lines from populations: Uman’, Inkerman, Odesa, Varva, Kyiv, Drogobych, Yaniv, Poliske, Chornobyl, and Chornobyl Nuclear Power Plant (NPP). The ambient radiation (µSv/h) was measured in the sample sites. The flies were reared in the laboratory through two generations. We carried out the observation of F2 flies for visibly detectable phenotypes. According to whether the trait was inherited, observations were separated into three categories: with deviations of posterior cross-vein (C2) (incomplete penetrance), visible phenotypic changes (non-inherited) and mutations (inherited). Polymerase chain reaction (PCR) with primers specific to the 16S rRNA and Wolbachia surface protein (wsp) genes were used to determine infection presence in isofemale lines of the flies established for each population. Results. Examination of different phenotypes indicates that the highest mutation rate (but not C2 and not inherited changes) is in populations from Chornobyl Exclusion Zone and, therefore, connection with ambient radiation was detected (p = 0.0241). Generalized mixed linear regression has shown evidence that the presence of phenotypes with defects of C2 vein varies with endosymbiont infection presence (p = 0.03473) in the populations from radioactively polluted areas. Conclusion. Wolbachia is not related to occurring phenotypes neither with phenotypic changes nor with mutations, at least in surveyed populations. However, C2 defected phenotypes relates to the bacterial presence in populations from the contaminated area. Nonetheless, the origin of this relationship is unknown and the mechanisms of such a connection require further research. Keywords: Drosophila melanogaster, Wolbachia, endosymbiont, ambient radiation, mutation, phenotypic change, posterior cross-vein.