Juan José Fanara

Insecticides are valuable and widely used tools for the control of insect pests. However, we know very little about the genes and processes involved in the key steps of the poisoning sequence. Besides, the excessive and indiscriminate use of insecticides is generating mechanisms of resistance in various insect pests. To improve our understanding of insecticide toxicity, we need a powerful model organism to help describe the processes underlying insecticide poisoning and the use of genomic tools to identify and analyze the genetic basis of the toxicological response of the insecticides. In this context, we associate variation in toxicological response with genomic variation, to identify genetic polymorphisms underlying the different steps of the insect (genotype)‐response (phenotype)‐insecticide (environment) interaction. We investigate the genetic factors involved in the toxicological response of D. melanogaster lines when exposed to spinosad and lambda‐cyhalothrin through the measured of KT₅₀ in adult males. Since the genomes of all lines evaluated are completely sequenced, we performed a Genome Wide Association Study that enabled us to identify genetic polymorphisms and candidate genes responsible for the overall phenotypic variation. Most of the candidate genes detected exhibited insecticide‐specific effect and play roles in the toxicodynamics as AstC‐R1, Dh44‐R, stan, Ca‐β, AgmNAT, Acox57D‐d, Btk, CarT, dpr8, Pkd2, and Shab and the toxicokinetics like for example ckd, Hr38, robo2, Toll‐4, Eglp2, and Prip of spinosad and lambda‐cyhalothrin. Finally our results suggest that in the case of lambda‐cyhalothrin genotypes exhibiting resistance phenotypes (higher KT₅₀) also displaying a less constant (robust) response.

The history of biodiversity is closely related to the history of the evolution of species interactions. Diversity can be reduced by competitive exclusion in species with similar ecology that live in the same spatial region. Zaprionus indianus Gupta is a pest species that has colonized the American continent in the last 20 years. The expansion of this species in Argentina can generate competition, a major event of the ecology of insect communities exploiting ephemeral and fragmented resources. Zaprionus indianus has shown an overlapping in the breeding and feeding resources and in the distribution with Drosophila melanogaster Meigen and D. simulans Sturtevant in north-eastern Argentina. In this study, we analyzed the effect of interspecific competition between larvae of these species reared in cultured media prepared from three natural fruits. Our results revealed that D. simulans has a lower competitive ability with respect to the other species. On the other hand, both the successful colonization of Z. indianus and the differences observed in nature in the relative abundance of these three species between samples of collected and emerged adults cannot be attributed only to effects of interspecific competition.

The capacity to lay eggs inside healthy fruits rather than on decaying plant matter differentiates insect fruit pests from domestic species. This niche differentiation has been previously proposed to be an adaptation to avoid competition. We hypothesize that pest species will be more strongly affected by competition. We compare the impact of larvae density on fitness traits between Drosophila pests ( Drosophila suzukii (Matsumura, 1931); Zaprionus indianus Gupta, 1970) and domestic species ( Drosophila immigrans Sturtevant, 1921; Drosophila melanogaster Meigen, 1830). We assessed the effect of crowding on adult emergence and development time. Viability decreased gradually with density for D. immigrans and D. suzukii, while for D. melanogaster and Z. indianus it remained high. Development time increased with density; this was stronger on Z. indianus and D. immigrans than on D. suzukii, which had a moderate increase, and D. melanogaster, which did not change. Contrary to expectations, the distinct patterns observed were not related to each species' domestic or pest lifestyle. In fact, patterns consistent with either scramble or contest type of competition were observed on both pest and domestic species, respectively. These findings challenge prior beliefs regarding competition effects among Drosophila pest species and provide information relevant to integrated pest management.

Dehydration is a stress factor for organisms inhabiting natural habitats where water is scarce. Thus, it may be expected that species facing arid environments will develop mechanisms that maximize resistance to desiccation. Insects are excellent models for studying the effects of dehydration as well as the mechanisms and processes that prevent water loss since the effect of desiccation is greater due to the higher area/volume ratio than larger animals. Even though physiological and behavioral mechanisms to cope with desiccation are being understood, the genetic basis underlying the mechanisms related to variation in desiccation resistance and the context-dependent effect remain unsolved. Here we analyze the genetic bases of desiccation resistance in Drosophila melanogaster and identify candidate genes that underlie trait variation. Our quantitative genetic analysis of desiccation resistance revealed sexual dimorphism and extensive genetic variation. The phenotype-genotype association analyses (GWAS) identified 71 candidate genes responsible for total phenotypic variation in desiccation resistance. Half of these candidate genes were sex-specific suggesting that the genetic architecture underlying this adaptive trait differs between males and females. Moreover, the public availability of desiccation data analyzed on the same lines but in a different lab allows us to investigate the reliability and repeatability of results obtained in independent screens. Our survey indicates a pervasive micro-environment lab-dependent effect since we did not detect overlap in the sets of genes affecting desiccation resistance identified between labs.

Insect flight is a complex trait involved in different behaviors, from the search for sexual partners, food, or breeding sites. Many studies have postulated the adaptive advantages of certain morphological traits in relation to increased flight capacity, such as low values of wing loading or high values of wing:thorax ratio and wing–aspect ratio. However, few studies have evaluated the relationship between variables related to flight and morphological traits in Drosophila. This work aimed to study morphological traits in males and females of two pairs of sibling species: Drosophila buzzatii Patterson and Wheeler‐Drosophila koeferae Fontdevila and Wasserman, and Drosophila melanogaster Meigen‐Drosophila simulans Sturtevant, and to analyze its relationship with flight. We detected the highest proportion of flight time in D. koepferae and D. simulans compared to D. buzzatii and D. melanogaster, respectively. Our results also revealed sexual dimorphism, with males exhibiting a higher proportion of flight time than females. Surprisingly, we did not find a general pattern to explain the relationship between morphology and the proportion of flight time because associations varied depending upon the analyses (considering all groups together or each sex‐species combination separately). Moreover, these associations explained a low percentage of variation, suggesting that other nonmorphological components related to flight, such as physiological variables, should be taken into account. This work allowed us to show the variability and complexity of an aspect of flight, suggesting that the adaptive role of the morphological traits studied might have been overestimated.

Dehydration is a stress factor that affects organisms in certain natural habitats, so it is to be expected that populations will develop mechanisms that maximize resistance to desiccation. Insects are an excellent model for studying the effects of dehydration as well as the mechanisms and processes that prevent the effects of water loss since the effect of desiccation is greater owing to the higher area: volume ratio than larger animals. Even though physiological and behavioral mechanisms to cope with desiccation are being understood, the genetic basis underlying the mechanisms related to variation in desiccation resistance and the context-dependent effect remain unresolved. We analyzed the genetic bases of desiccation resistance in Drosophila melanogaster and identified candidate genes that underlie trait variation. Our quantitative genetic analysis of variation in desiccation resistance revealed sexual dimorphism and extensive genetic variation. The phenotype-genotype association analyses (GWAS) identified 71 candidate genes responsible for total phenotypic variation in desiccation resistance. Half of these candidate genes were sex-specific suggesting that the genetic architecture underlying this adaptive trait differs between males and females. Moreover, the public availability of desiccation data analyzed on the same lines but in a different lab allows us to investigate the reliability and repeatability of the results obtained in independent phenotype screens. These analyses indicate a pervasive micro-environment lab-dependent effect since we did not detect overlap between our own estimates of desiccation resistance and the results obtained in another lab.

Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) is an invasive pest species that uses a wide variety of commercial fruit as a breeding and feeding resource. The damage to the fruit generated by D. suzukii´ oviposition causes considerable economic losses. Therefore, the maintenance of D. suzukii in the lab conditions constitutes a fundamental tool for research proposal. Two of the determining factors affecting the lab rearing conditions are the culture medium and density. In this study, we evaluated the impact of these factors on three components associated with fitness: development time, larval-adult viability and body size, comparing the effects of three culture media: cornmeal (polenta), mashed potato and plum when the flies were reared at three densities: 10, 30 and 50 larvae per 5ml of culture medium. Our results revealed that the flies reared the cornmeal culture medium and at lower densities provide the better conditions for the maintenance of D. suzukii under lab conditions.

Drosophila suzukii Matsumura, 1931 (Diptera: Drosophilidae) is an invasive pest species that causes damage to fruit crops due to premature deterioration of ripe fruits by oviposition inside them. A review of D. suzukii detections in Argentina was carried out and we updated this list with the results of our sampling in the Northwest, Cuyo and Northeast regions. The surveys carried out determined the first detections in the provinces of Jujuy and Córdoba, revealing the continuous geographical expansion of this species.

In phytophagous insects, oviposition behaviour is an important component of habitat selection and, given the multiplicity of genetic and environmental factors affecting its expression, is defined as a complex character resulting from the sum of interdependent traits. Here, we study two components of egg‐laying behaviour: oviposition acceptance (OA) and oviposition preference (OP) inDrosophila melanogasterusing three natural fruits as resources (grape, tomato and orange) by means of no‐choice and two‐choice experiments, respectively. This experimental design allowed us to show that the results obtained in two‐choice assays (OP) cannot be accounted for by those resulting from no‐choice assays (OA). Since the genomes of all lines used are completely sequenced, we perform a genome‐wide association study to identify and characterize the genetic underpinnings of these oviposition behaviour traits. The analyses revealed different candidate genes affecting natural genetic variation of both OA and OP traits. Moreover, our results suggest behavioural and genetic decoupling between OA and OP and that egg‐laying behaviour is plastic and context‐dependent. Such independence in the genetic architectures of OA and OP variation may influence different aspects of oviposition behaviour, including plasticity, canalization, host shift and maintenance of genetic variability, which contributes to the adoption of adaptive strategies during habitat selection.