Reasons for success: Rapid evolution for desiccation resistance and life-history changes in the polyphagous flyAnastrepha ludens

A trade-off between desiccation resistance and developmental humidity for pupation height in the North Indian seasonal population of Drosophilid-Zaprionus indianus

Drosophila larvae and pupae are vulnerable to seasonal abiotic stressors such as humidity and temperature. In wild low-humidity habitats, desiccation stress can occur as Drosophila larvae forsake wet food in search of a drier pupation site. Henceforth, the hypothesis that developmental humidity impacts pupation height, affecting larval and pupae water balance and fitness-related traits, was examined. Accordingly, warm-adapted Drosophilid- Zaprionus indianus from two seasons were reared under season-specific simulated conditions, with significantly varying relative humidity (summer RH: 40%; rainy RH: 80%), but nearly identical temperatures. A trade-off between pupation height and developmental humidity was observed. Drier summer conditions lead to pupae wandering farther from drier glass surfaces, resulting in higher pupation height (17.3 cm) while rainy pupae prefer wet food, resulting in lower pupation height (7.12 cm). Additionally, density-dependent pupation height was developmental humidity-specific, with most rainy-season pupae pupated on wetter food, while dry summer pupae pupated on glass surfaces or cotton. Nevertheless, flies from far pupation exhibited greater desiccation resistance, fecundity, and copulation duration than those from near pupation. The cuticular lipid mass of larvae and pupae was higher during far-than-near pupation, indicating decreased water loss rates compared to near-pupation. Finally, pupae eclosion (%) was unaffected by greater humidity (85%) in either season. Still, it considerably decreased at lower humidity (RH: 0% and 38%) for rainy pupae, further supporting the selection of low-humidity desiccation resistance in pupae. In conclusion, low humidity is crucial for survival of pre-adult stages of Zaprionus indianus under desiccation stress and for preference of pupation site.

Reproductive behavior of fruit flies: courtship, mating, and oviposition

Many species of the Tephritidae family are invasive and cause huge damage to agriculture and horticulture, owing to their reproductive characteristics. In this review, we have summarized the existing studies on the reproductive behavior of Tephritidae, particularly those regarding the genes and external factors that are associated with courtship, mating, and oviposition. Furthermore, we outline the issues that still need to be addressed in fruit fly reproduction research. The review highlights the implications for understanding the reproductive behavior of fruit flies and discusses methods for their integrated management and biological control. © 2023 Society of Chemical Industry.

Raspberry ketone feeding makes Queensland fruit fly, Bactrocera tryoni (Froggatt), more vulnerable to desiccation but not starvation

BACKGROUND

Queensland fruit fly (Qfly) males exhibit accelerated sexual maturation when their diet is supplemented with raspberry ketone (RK) for 48 h following emergence, which is beneficial for sterile insect technique operation. The present study tests whether RK supplementation makes Qfly more vulnerable to starvation or desiccation.

RESULTS

Flies were fed for 48 h with a yeast hydrolysate and sugar diet (1:3) that contained 0% RK (control), 1.25% RK (low dose) or 5% RK (high dose) to test subsequent vulnerability to starvation and desiccation. RK feeding decreased body weight and water content in males and increased lipid levels in both sexes before exposure to any stress treatment. Under nutritional stress, flies fed the low RK dose, but not the high RK dose, had higher survival than controls. Under desiccation stress, flies fed both the low and high RK doses had lower survival than the controls. Body weight, water content and lipid reserves at death were all affected by RK dose when under nutritional stress, but not when under desiccation stress. In the absence of stress, body weight at death was higher than controls in flies provided with the high RK dose and lipids were lower than controls in flies provided with the low RK dose.

CONCLUSION

Feeding with RK makes Qflies more vulnerable to desiccation but not starvation. In most conditions, it is expected that the disadvantage of increased desiccation vulnerability would be outweighed by the benefits of accelerated sexual maturation in RK-fed young adult Qflies. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Maximum Entropy (MaxEnt) as extreme distribution indicator of two Neotropical fruit fly parasitoids in irrigated drylands of Argentina

The figitid Ganaspis pelleranoi and the braconid Doryctobracon areolatus (Hym: Braconidae, Opiinae) are wide-ranging (from Florida, USA to Argentina) fruit fly parasitoids with tropical and subtropical distribution with a wet and temperate climate. In Argentina, both parasitoid species are thought to be restricted to the subtropical rainforests of the northwest and northeast, locally known as 'Yungas' and 'Paranaense' forests, respectively. However, these species recently have been recorded at the Monte and Thistle of the Prepuna eco-region, an arid region of central-western Argentina. Despite the extreme environmental conditions, anthropic artificial irrigation seems to be playing a fundamental role in fostering the presence and persistence of these species. Maximum Entropy (MaxEnt) models were developed to assess the suitability of these areas to harbor both species. The present work is a first approach to identify suitable areas for the distribution of these two fruit fly biological control agents in the American continent; based on 19 bioclimatic variables. Furthermore, the models resulting from including the new records in the 'Monte' eco-region suggest that local populations may become adapted to particular micro-environmental conditions generated by artificial irrigation. Models revealed that these artificial oases are suitable for G. pelleranoi but seem to be unsuitable for D. areolatus. This first and new approach to the area suitability of these species invites to produce models that reflect actual distribution including more records of presence in oases with similar conditions, thus decreasing the bias of the model generated by over reliance on areas with higher humidity (forest), which correspond to the distribution known before the inclusion of the new records.

Interaction effects of desiccation and temperature stress resistance across Spodoptera frugiperda (Lepidoptera, Noctuidae) developmental stages

Insects encounter multiple overlapping physiologically challenging environmental stressors in their habitats. As such, the ability of insects to withstand these stressors singly or interactively is fundamental in population persistence. Following its invasion in Africa, Spodoptera frugiperda (Lepidoptera: Noctuidae) has successfully established and spread in most parts of the continent. However, the mechanisms behind its successful survival across arid and semi-arid African environments are relatively unknown. Here, we investigated the water balance of S. frugiperda across its developmental stages. Given the relationships between desiccation stress, temperature stress and other life history traits in arid ecosystems, we also measured interaction effects across metrics of these traits. Specifically, we measured basal body water content (BWC), water loss rates (WLRs) and the effects of desiccation pre-treatment on critical thermal minimum (CTmin), critical thermal maximum (CTmax) and fecundity. Body water content and WLR increased with age across larval instars. However, the effects of desiccation environments on WLRs were more dramatic for 5th and 6th larval instars. The 5th and 6th instars exhibited highest BWC and magnitude of WLRs plastic responses following desiccation treatment. The effects of desiccation pre-treatment on temperature tolerance were less apparent, only significantly improving CTmin in 2nd and 3rd larval instars and reducing CTmax in 5th instars. In addition, desiccation pre-treatment showed no significant effects on fecundity. These results show that water balance traits differ with developmental stage, while the effects of desiccation pre-treatment were more dramatic and inconclusive. The differential desiccation resistance, high proportional BWC and no desiccation pre-treatment effects on fecundity may help the species survive in arid and semi-arid environments. This information provides insights into understanding S. frugiperda survival under desiccating arid and semi-arid tropical environments and is significant in predicting pest outbreaks.

Post-mating gene expression of Mexican fruit fly females: disentangling the effects of the male accessory glands

Mating has profound physiological and behavioural consequences for female insects. During copulation, female insects typically receive not only sperm, but a complex ejaculate containing hundreds of proteins and other molecules from male reproductive tissues, primarily the reproductive accessory glands. The post-mating phenotypes affected by male accessory gland (MAG) proteins include egg development, attraction to oviposition hosts, mating, attractiveness, sperm storage, feeding and lifespan. In the Mexican fruit fly, Anastrepha ludens, mating increases egg production and the latency to remating. However, previous studies have not found a clear relationship between injection of MAG products and oviposition or remating inhibition in this species. We used RNA-seq to study gene expression in mated, unmated and MAG-injected females to understand the potential mating- and MAG-regulated genes and pathways in A. ludens. Both mating and MAG-injection regulated transcripts and pathways related to egg development. Other transcripts regulated by mating included those with orthologs predicted to be involved in immune response, musculature and chemosensory perception, whereas those regulated by MAG-injection were predicted to be involved in translational control, sugar regulation, diet detoxification and lifespan determination. These results suggest new phenotypes that may be influenced by seminal fluid molecules in A. ludens. Understanding these influences is critical for developing novel tools to manage A. ludens.

Invasive potential of tropical fruit flies in temperate regions under climate change

Tropical fruit flies are considered among the most economically important invasive species detected in temperate areas of the United States and the European Union. Detections often trigger quarantine and eradication programs that are conducted without a holistic understanding of the threat posed. Weather-driven physiologically-based demographic models are used to estimate the geographic range, relative abundance, and threat posed by four tropical tephritid fruit flies (Mediterranean fruit fly, melon fly, oriental fruit fly, and Mexican fruit fly) in North and Central America, and the European-Mediterranean region under extant and climate change weather (RCP8.5 and A1B scenarios). Most temperate areas under tropical fruit fly propagule pressure have not been suitable for establishment, but suitability is predicted to increase in some areas with climate change. To meet this ongoing challenge, investments are needed to collect sound biological data to develop mechanistic models to predict the geographic range and relative abundance of these and other invasive species, and to put eradication policies on a scientific basis.

The Sterile Insect Technique: Success and Perspectives in the Neotropics

The sterile insect technique (SIT), an environmentally friendly means of control, is currently used against plant, animal, and human pests under the area-wide integrated pest management. It consists in the mass production, sterilization, and release of insects in an affected area where sterile males mate with wild females leading to no reproduction. Here, we review SIT in the Neotropics and focus on particular recent successful cases of eradication of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), as well as effective programs used against the Mexican fruit fly Anastrepha ludens (Loew), the New World screwworm fly Cochliomyia hominivorax (Coquerel)), and the Cactus moth Cactoblastis cactorum (Berg). We examine when SIT does not work and innovations that have made SIT more efficient and also highlight complimentary techniques that can be used in conjunction. We address potential candidate species that could be controlled through SIT, for example Philornis downsi Dodge & Aitken. Finally, we consider the impact of climate change in the context of the use of the SIT against these pests. Given the recent dramatic decline in insect biodiversity, investing in environmentally friendly means of pest control should be a priority. We conclude that SIT should be promoted in the region, and leadership and political will is needed for continued success of SIT in the Neotropics.

Combined Effects of Methoprene and Metformin on Reproduction, Longevity, and Stress Resistance in Anastrepha ludens (Diptera: Tephritidae): Implications for the Sterile Insect Technique

Survival and mating success are traits of quality in mass-reared sterile males. Thus, studying the trade-offs between these traits may help to improve process in the sterile insect technique (SIT). Here, we tested the hypothesis that modifying individual metabolism, especially of energetic reserves, may reduce the negative impact of an early reproduction on the survival of Anastrepha ludens flies. Appling metformin (a drug used to treat type II diabetes) that improves insects' survival, through dietary restriction mimicry, and methoprene (a juvenile hormone analogue) that accelerates the age to reproduction in insects, we explore the dynamic of this trade-off. We fed A. ludens flies with metformin, methoprene, or a mixture of metformin-methoprene for five consecutive days. We determined the effect of these treatments on the fecundity and fertility (number of eggs and percentage of hatching) of females, on sexual maturation and mating success of males, and on the survival of both sexes. The results showed that the acceleration in sexual maturation by the action of methoprene significantly reduced survival in both sexes of two different fly strains. However, adding metformin to the diet buffered this negative effect, without reducing the mating propensity compared with the males treated only with methoprene. The response to metformin was sex-specific since females responded to high doses of the substance, whereas males responded better to low doses. These results suggest that trade-offs between survival and reproduction do not necessarily depend on energy reserves but they are intrinsically related to metabolic regulation and hormonal control.

Desiccation limits recruitment in the pleometrotic desert seed-harvester ant Veromessor pergandei

The desert harvester ant Veromessor pergandei displays geographic variation in colony founding with queens initiating nests singly (haplometrosis) or in groups (pleometrosis). The transition from haplo- to pleometrotic founding is associated with lower rainfall. Numerous hypotheses have been proposed to explain the evolution of cooperative founding in this species, but the ultimate explanation remains unanswered. In laboratory experiments, water level was positively associated with survival, condition, and brood production by single queens. Queen survival also was positively influenced by water level and queen number in a two-factor experiment. Water level also was a significant effect for three measures of queen condition, but queen number was not significant for any measure. Foundress queens excavated after two weeks of desiccating conditions were dehydrated compared to alate queens captured from their natal colony, indicating that desiccation can be a source of queen mortality. Long-term monitoring in central Arizona, USA, documented that recruitment only occurred in four of 20 years. A discriminant analysis using rainfall as a predictor of recruitment correctly predicted recruitment in 17 of 20 years for total rainfall from January to June (the period for mating flights and establishment) and in 19 of 20 years for early plus late rainfall (January-March and April-June, respectively), often with a posterior probability > 0.90. Moreover, recruitment occurred only in years in which both early and late rainfall exceeded the long-term mean. This result also was supported by the discriminant analysis predicting no recruitment when long-term mean early and late rainfall were included as ungrouped periods. These data suggest that pleometrosis in V. pergandei evolved to enhance colony survival in areas with harsh abiotic (desiccating) conditions, facilitating colonization of habitats in which solitary queens could not establish even in wet years. This favorable-year hypothesis supports enhanced worker production as the primary advantage of pleometrosis.

Climate stress resistance in male Queensland fruit fly varies among populations of diverse geographic origins and changes during domestication

Background

The highly polyphagous Queensland fruit fly (Bactrocera tryoni Froggatt) expanded its range substantially during the twentieth century and is now the most economically important insect pest of Australian horticulture, prompting intensive efforts to develop a Sterile Insect Technique (SIT) control program. Using a “common garden” approach, we have screened for natural genetic variation in key environmental fitness traits among populations from across the geographic range of this species and monitored changes in those traits induced during domestication.

Results

Significant variation was detected between the populations for heat, desiccation and starvation resistance and wing length (as a measure of body size). Desiccation resistance was correlated with both starvation resistance and wing length. Bioassay data for three resampled populations indicate that much of the variation in desiccation resistance reflects persistent, inherited differences among the populations. No latitudinal cline was detected for any of the traits and only weak correlations were found with climatic variables for heat resistance and wing length. All three stress resistance phenotypes and wing length changed significantly in certain populations with ongoing domestication but there was also a strong population by domestication interaction effect for each trait.

Conclusions

Ecotypic variation in heat, starvation and desiccation resistance was detected in Australian Qfly populations, and these stress resistances diminished rapidly during domestication. Our results indicate a need to select source populations for SIT strains which have relatively high climatic stress resistance and to minimise loss of that resistance during domestication.

Does the Effect of Irradiation Dose Vary Between Flies Selected and Non-selected to Resist Desiccation? The Case of Anastrepha ludens (Diptera: Tephritidae)

The sterile insect technique (SIT), used to control different species of tephritid fruit flies (Diptera: Tephritidae), is an important element in sustainable agriculture because of its low negative impact on the environment. In SIT, flies are mass produced and sterilized in the laboratory and then released in a target area. However, once released, laboratory flies may confront harass environments that would reduce their performance and consequently SIT efficiency. Selecting flies that resist stressful conditions may help to improve the efficiency of the SIT by releasing males that resist desiccation, for example, ensuring, thus, their survival in environments with low relative humidity. However, the selection process may affect the resistance of flies to the stress of sterilization, since some life history traits are affected. Here, we studied the effect of irradiation on Anastrepha ludens (Loew) (Diptera: Tephritidae) desiccation resistant flies (DR) compared with nonselected flies (NS). We measured the effect of gamma irradiation dose (0, 20, 40, 60, and 80 Gy) on sterility (males and females) and quality parameters (emergence, flight ability, survival, and male sexual performance) in A. ludens adults of the DR and NS (control) strains. Our results indicate that irradiation affected equally the sterility of adults of both strains. None of the quality parameters differed between strains. The only difference was that DR flies survived longer than control flies. Thus, flies that are resistant to desiccation can be used in the SIT without altering the current process of irradiation and packing.

Forecast of export demand based on artificial neural network and fuzzy system theory

This paper analyses the significance and methods of foreign trade export forecasting. The index system of foreign trade export forecasting is determined based on the analysis of foreign trade export forecasting research results. The concepts and principles of artificial neural network and fuzzy system theory are expounded, and their respective advantages and disadvantages as well as their complementarities are analyzed. This paper introduces the types and training algorithms of evolutionary morphological neural network, combines the neural network with the fuzzy system theory, and establishes the prediction model. Finally, the evolutionary morphological neural network model is applied to the prediction of foreign trade export in view of the characteristics of export and considering the influence of various factors, the whole process of establishing evolutionary morphological neural network forecasting model is introduced in detail, and the change range of export is predicted, and the ideal forecasting results are obtained.

Behavioral Responses and Pupa Development Patterns After Hypoxia or Anoxia in a Desiccation-Resistant Anastrepha ludens Strain

The aim of this study was to experimentally test for adult cross-resistance to hypoxia or anoxia in a desiccation-resistant population of Anastrepha ludens Loew. We compared desiccation resistant flies with unselected (control) flies by measuring the effect of pre-emergence hypoxia on some fitness parameters (emergence, flight ability, copulation success, latency to copulation, copulation duration, ovary size). Anoxia effects were determined using eye color changes during pupa development and fly emergence after re-oxygenation. Both strains were negatively affected in all measured parameters when exposed to hypoxia for more than 48 h. However, after hypoxia, control flies showed, in general, shorter latency to mate and longer copula duration than desiccation-resistant flies. Anoxia-induced arrest of pupa development, whereas returning to normoxia conditions induced resumption of development. Anoxia period length (longer than 72 h) increased mortality to 100% in the control line, whereas the desiccation-resistant line survived even at 120 h of anoxia. Thus, pre-release hypoxia must not exceed 24 h in order to maintain insect quality independently of fly type.

Survival ability of Mexican fruit fly males from different strains in presence of the predatory orb-weaving spider Argiope argentata (Araneae: Araneidae)

The sterile insect technique (SIT) is a key element for the integrated management of pest populations of the Mexican fruit fly, Anastrepha ludens, in Mexico. Its success depends on the survival of mass-reared sterile males and their ability to mate with wild females. However, colonization and mass-rearing conditions can adversely affect their ability to avoid predators. To test if colony management strategies could contribute to improve field survival abilities of mass-reared flies, we compared the survival of males exposed to the orb-weaver spider Argiope argentata. Males compared originated from three strains with different colonization strategies: (a) a colony started from field-collected wild flies (replacement), (b) a colony started by hybridizing wild males with mass-reared adapted females (hybrid) and (c) a colony started with mass-reared males selected on the basis of their survival ability and mating competitiveness in field cages (selected). Mass-reared males and wild males were used as controls. Males were exposed to spiders under laboratory cage conditions. Overall, wild males showed better survival ability than mass-reared males. Regarding the colonization approach, wild males survived better than a hybrid, replaced and selected males. We conclude that mass-rearing conditions have a strong negative effect on the ability of males to escape spiders. The colonization systems evaluated did not counter this effect. The lower survival of males from the selected colony suggests that the selection over one generation did not contribute to improve males' predator avoidance and escape abilities and probably needs to be modified. Possible explanations for this and implications on colonization and colony management for SIT purpose are discussed.

Directional selection to improve the sterile insect technique: Survival and sexual performance of desiccation resistant Anastrepha ludens strains

The sterile insect technique (SIT) is an effective, environmentally friendly method for insect control whose success depends on the sexual performance and survival of sterile males. These two parameters are influenced by environmental conditions of target areas, and releasing insects with a higher tolerance to stressful environments can improve SIT efficiency. Directional selection can be used to produce insect strains with higher tolerance to extreme environmental conditions, such as low humidity, for extended periods. We evaluated, under field cage conditions, the sexual competitiveness, sexual compatibility, and survival of strains of Anastrepha ludens (Loew) selected for desiccation resistance to determine the value of directional selection as a possible approach to enhance SIT efficiency. Fly strains (selected and unselected and those mass-reared) were exposed to stressful conditions of low humidity and food and water deprivation for 24 hr before test. As a control, mild conditions without the stressors were used. No differences in sexual competitiveness and sexual compatibility between selected, nonselected, and mass-reared strains were observed when previously exposed to mild conditions. Thus, selection for desiccation resistance does not modified negatively the sexual performance. However, when insects were exposed to stressful conditions, males of selected strains sexually outperform mass-reared males. Additionally, selected strains presented higher survival than mass-reared flies. The approach to integrate directional selection with other technologies in the SIT as well as the implications of using a desiccation-selected strain in the current pest management program is discussed.

Effects of temperature and drought on early life stages in three species of butterflies: Mortality of early life stages as a key determinant of vulnerability to climate change?

Anthropogenic climate change poses substantial challenges to biodiversity conservation. Well‐documented responses include phenological and range shifts, and declines in cold but increases in warm‐adapted species. Thus, some species will suffer while others will benefit from ongoing change, although the biological features determining the prospects of a given species under climate change are largely unknown. By comparing three related butterfly species of different vulnerability to climate change, we show that stress tolerance during early development may be of key importance. The arguably most vulnerable species showed the strongest decline in egg hatching success under heat and desiccation stress, and similar pattern also for hatchling mortality. Research, especially on insects, is often focussed on the adult stage only. Thus, collating more data on stress tolerance in different life stages will be of crucial importance for enhancing our abilities to predict the fate of particular species and populations under ongoing climate change.