Drosophila Immigrans Research Articles

Density-dependent development in pest and domestic Drosophilidae species

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.

Simple and Rapid PCR-RFLP based species identification in Drosophila suzukii and Drosophila immigrans larvae

Wild fruit fly larvae can be distinguished at the family level such as Drosophilidae and Tephritidae larvae are based on size or spiracles arrangement, but such visual distinction is more intricate between Drosophilid species. In the present study, to identify the Drosophila immigrans and Drosophila suzukii species at the larval stage, we employed a simple, rapid PCR-RFLP experiment. Wild suspected larvae from Drosophila immigrans and Drosophila suzukii species were collected from 3 different geographical regions. DNA was isolated and a PCR-RFLP profile was developed using the XmnI restriction enzyme. Sequencing of the mitochondrial COI gene from larvae was performed to evaluate the species. PCR-RFLP analysis from Drosophila suzukii wild larvae generated three distinct bands with 120bp, 210bp and 250bp. Similarly, Drosophila immigrans generated 2 distinct bands with 270bp and 310bp. Restriction digestion products from both the larvae and adult flies were the same, hence the accuracy of the PCR-RFLP profile developed from both suspected wild larvae and adult flies was 100%. Sequencing analysis confirms that wild field collected larvae belong to Drosophila suzukii and Drosophila immigrans. Present study clearly shows that PCR‐RFLP is a fast, simple, inexpensive and accurate molecular method and it can be successfully used for species identification at the early stages of the life cycle of Drosophila species.

Mitochondrial polymorphism shapes intrapopulation behavioural variation in wild Drosophila.

Intrapopulation variation in behaviour, including activity, boldness and aggressiveness, is becoming more widely recognized and is hypothesized to substantially affect ecological and evolutionary dynamics. Although previous studies used candidate-gene approaches and genome-wide association analyses to identify genes correlated with variations in activity and aggressiveness, behavioural variation may not be fully captured in the nuclear genome, as it does not account for mitochondrial genomes. Mitochondrial genes encode products that are key regulators of the cellular energy-producing pathways in metabolic processes and are thought to play a significant role in life-history and reproductive traits. In this study, we considered many isofemale lines of Drosophila immigrans established from two wild populations to investigate whether intrapopulation variation in the mitochondrial genome affected activity level within this species. We identified two major haplogroups in these populations, and activity levels in both larvae and adults differed significantly between the two haplogroups. This result indicated that intrapopulation variation in activity level may be partially controlled by mitochondrial genes, along with the interaction between nuclear and mitochondrial genes and the age of individual organisms.

Demographic parameters of Trichopria drosophilae in three host species

AbstractTrichopria drosophilae Perkins (Hymenoptera: Diapriidae) is a cosmopolitan endoparasitoid of the pupal stages of Drosophila suzukii Matsumura (Diptera: Drosophilidae) and other Drosophila species around the world. It is also considered as a potential biocontrol agent of this pest. Here we describe the effects of three hosts (D. suzukii, Drosophila melanogaster Meigen, and Drosophila immigrans Sturtevant) on the demographic parameters of T. drosophilae. Adult female T. drosophilae that emerged from D. immigrans and D. suzukii were larger than those that emerged from D. melanogaster. Fertility was 18% greater for T. drosophilae that developed on D. immigrans and D. suzukii, compared with those developing on D. melanogaster. The net reproductive rate of T. drosophilae was higher on D. immigrans and D. suzukii (R0 = 25.25 and 26.51) than on D. melanogaster (R0 = 22.53). However, the generation time was longer on D. immigrans and D. suzukii (T = 20.38 and 19.59 days, respectively) than on D. melanogaster (T = 17.20 days), perhaps due to their larger size. This favored the intrinsic rate of natural increase of T. drosophilae reproducing on D. melanogaster (rm = 0.181) compared with those reproducing on D. immigrans and D. suzukii (rm = 0.158 and 0.167, respectively). Parasitism rate of D. suzukii by T. drosophilae was 53% regardless of the host species from which the parasitoid had emerged. The implications of these results are discussed in the context of biological control of D. suzukii.

Intrapopulation genetic variation in the level and rhythm of daily activity in Drosophila immigrans.

Genetic diversity within a population, such as polymorphisms and personality, is considered to improve population performance because such intraspecific variations have the potential to alleviate the competition for a limited resource or the risk of predation and sexual harassment at a population level. Variation in the level and rhythm of daily activity in a population could also affect population performance by directly altering ecological, social, and sexual interactions among individuals. However, it remains to be elucidated whether such intra‐population variation in the level and rhythms of daily activity exists in a natural population. Here, we investigated the genetic variation in daily activity within a single natural population of Drosophila immigrans. We established 21 isofemale lines from a single natural population and measured larval activity level and the level and daily pattern of adult activity over a 24 hr period. Larval activity level significantly varied among isofemale lines. Likewise, the activity level in the adult stage significantly varied among lines. The significant variation was also found in the daily pattern of adult activity; some lines showed greater activity level in the daytime, and others showed greater activity level in the night. Our results consistently suggest that there is a genetic variation in behavioral activity in a natural population, probably contributing to shaping the population performance.

Allopatric sibling species pair Drosophila nasuta nasuta and Drosophila nasuta albomicans exhibit expression divergence in ovarian transcriptomes.

Drosophila nasuta nasuta and Drosophila nasuta albomicans represent cross fertile members of the immigrans species group of Drosophila with an allopatric mode of distribution exhibiting characteristic novelties. Illumina sequencing technology and de novo transcriptome assembling strategies were used for the current study. The analysis revealed 8% of the transcriptome to be differentially expressed between the ovaries of these two species, of which 9% was related to female reproduction. The majority of the differentially expressed genes were enriched for genetic information processing pathways, biosynthesis, and metabolism-related pathways. SNPs in D. n. albomicans transcriptome was double in number than in D. n. nasuta and only 5% of these SNPs were fixed. Ka/Ks ratios indicated the lineages were under strong purifying selection. The genes which are differentially expressed are evolving at a similar rate as that of genes with conserved expression. Thus, the current findings provide useful insights on the expression dynamics during incipient species divergence of D. n. nasuta and D. n. albomicans since their divergence time of~0.5 million years.

Production and evolution pattern of “fruity smell” aggregation pheromones in genus Drosophila

AbstractInsects produce pheromones to serve a range of ecological functions throughout their lifetime. The chemical composition, production pattern, and interspecies specificity provide information for carrying out their function and biological significance. Several species of Drosophila produce a class of volatile esters considered as “fruity smells”; however, the production pattern and ecological functions of these “fruity smell” volatiles in genus Drosophila are poorly understood. Here, using the headspace solid‐phase microextraction (SPME) method, we tested the production pattern of volatile pheromones in Drosophila immigrans and factors that possibly affected pheromone production, including mating, feeding conditions, age of adult flies, and geographical distribution. We also explored the evolution and production pattern of volatile pheromones in 14 species of genus Drosophila. Our result showed that male D. immigrans adult flies produce three male‐specific volatile ester pheromones, which are also considered as “fruity smell” chemicals, in a relatively stable pattern. In addition, a series of “fruity smell” ester pheromones with similar structure and chemical properties were found to appear in the species of D. virilis and D. immigrans species group, but not in the species of D. melanogaster species group. The ester volatile pheromone production of male flies has a correspondence with the female's demand for host plants. Integrating the production and evolution pattern of these volatile chemicals, we inferred the interaction between insects and host plants reflected in the Drosophila “fruity smell” pheromones.

Comparison of the Antennal Sensilla and Compound Eye Sensilla in Four Drosophila (Diptera: Drosophilidae) Species

Antennal sensilla and compound eyes of fruit flies, Drosophila melanogaster (Meigen), Drosophila suzukii (Matsumura), Drosophila immigrans (Sturtevant), and Drosophila hydei (Sturtevant) (all Diptera: Drosophilidae), were observed with stereoscopic microscopy and scanning electron microscopy. The results showed that the antenna consists of 3 segments: a proximal scape, a pedicel, and a flagellum composed of a funiculus and a dendritic arista. Six morphologically distinct types of sensilla were observed on the antenna: chaetica, microtrichia, trichoid (Tr I, Tr II), basiconic, clavate, and coeloconic (Co I, Co II). Basiconic sensilla were significantly shorter than other sensilla in the funiculus of D. melanogaster. The number of clavate sensillae was less than other sensilla in the funiculus of D. melanogaster and D. immigrans, but was greater in D. suzukii and D. hydei. Moreover, coeloconic sensilla were absent in D. suzukii and D. hydei. The length and abundance of the chaetica sensilla on the compound eyes were different significantly among the 4 species. Drosophila hydei had chaotic sensilla with the greatest length and abundance; they were lowest for D. suzukii. Based on the previous literature, the possible functions of these sensilla are discussed. We inferred that fruit flies may regulate their behaviors according to the information detected by these sensilla.

Effect of Cherry Cultivar and Trapping Height on Population Dynamics of Drosophila Fruit Flies in Cherry Orchards in Northern China

In recent years, fruit flies (Drosophila spp.: Drosophilidae) have become an increasingly serious problem for cherry production in northern China. In this study, we examined the species composition and dynamics of fruit flies in cherry orchards using lure-baited traps placed at different heights, and in 3 different cherry cultivars, from Apr through Sep 2014 to 2016 in Qingdao, Shandong Province, China. The total number of fruit flies increased from yr to yr. Four species were captured: Drosophila melanogaster Meigen, Drosophila suzukii Matsumura, Drosophila hydei Sturtevant, and Drosophila immigrans Sturtevant (all Diptera: Drosophilidae). The dominant species was D. melanogaster, with 66.7% of the total captured, followed by D. suzukii (29.7%). Drosophila hydei and D. immigrans accounted for only 3.0 and 0.6%, respectively, and for these last 2 species, no peak period in abundance was observed. In general, Drosophila spp. appeared in Apr, and peaked around mid-Jul. Over the 3 yr span of the study, peak fruit fly abundance occurred later each yr, being at the end of Jun in 2014, and in the middle of Jul in 2015 and 2016. There were significant differences in the number of Drosophila species among cherry cultivars, as well as in the number of Drosophila trapped at different heights. The cultivar maturing in the middle of the season (cv. ‘Van') attracted the most fruit flies. The optimal height for trap placement was at 1 m above ground level, which is recommended as a standard height for Drosophila spp. population monitoring.

The development of drosophilid species (Diptera, Drosophilidae) in different strawberry cultivars

Drosophilids were not considered to be agricultural pests as they develop in overripe and fermented fruits. With the arrival of invasive species of Drosophila suzukii (Matsamura, 1931) in Europe the status of drosophilids was changed as the species is able to develop in healthy, unwounded and ripening fruits causing economic losses in production of softskinned fruits. The first economic damages from D. suzukii in Croatia where observed in production of fresh market strawberry. The aim of this study was to determine which species of drosophilids can develop in strawberry fruits. The samples of fruits of three strawberry cultivars (‘Albion’, ‘Portola’ and ‘San Andreas’) were collected during the harvest season of 2016 at greenhouse cultivation farm near Zagreb (N 45° 41′ 24″, E 16° 24′ 0″). From each cultivar 50 samples of fully ripened fruit were randomly selected and placed into the chamber for insect development to a specific temperature and humidity regime. After development of flies, three drosophilid species: Drosophila immigrans Sturtevant, 1921 ; Drosophila simulans Sturtevant, 1919 and D. suzukii were identified. An analysis of variance showed statistically more drosophilids in cultivar ‘Albion’ compared to the other two cultivars. It was concluded that species D. immigrans and D. simulans can also develop in strawberries and damage the fruits if the fruit is primarily damaged by D. suzukii and also that drosophilids prefer the cultivar ‘Albion’ for development.

Cold acclimation conditions constrain plastic responses for resistance to cold and starvation in Drosophila immigrans.

ABSTRACTIn montane Drosophila species, cold-induced plastic changes in energy metabolites are likely developed to cope with cold and starvation stress. Adult Drosophila immigrans reared at 15°C were acclimated at 0°C or 7°C for durations of up to 6 days (fed or unfed conditions). Such flies were tested for plastic changes in resistance to cold or starvation stress as well as for possible accumulation and utilization of four energy metabolites (body lipids, proline, trehalose and glycogen). Adults acclimated at 7°C revealed a greater increase in cold tolerance than flies acclimated at 0°C. Different durations of cold acclimation at 7°C led to increased level of body lipids only in fed flies which were utilized under starvation stress. However, such plastic responses were not observed in the flies acclimated at 0°C, which remained unfed due to chill-coma. These observations suggest a possible role of feeding to improve starvation resistance only in the flies acclimated at 7°C with food. Cold acclimated D. immigrans flies revealed improved cold resistance through a possible reshuffling of trehalose and glycogen; and starvation-induced proline which was utilized under cold stress durations. Finally, greater reduction in mean daily fecundity due to cold or starvation was observed in 0°C acclimated flies as compared to 7°C acclimated flies. Thus, cold acclimation conditions (0°C or 7°C) greatly impact resistance to cold and starvation in D. immigrans.

Evolving doublesex expression correlates with the origin and diversification of male sexual ornaments in the Drosophila immigrans species group.

Male ornaments and other sex-specific traits present some of the most dramatic examples of evolutionary innovations. Comparative studies of similar but independently evolved traits are particularly important for identifying repeated patterns in the evolution of these traits. Male-specific modifications of the front legs have evolved repeatedly in Drosophilidae and other Diptera. The best understood of these novel structures is the sex comb of Drosophila melanogaster and its close relatives. Here, we examine the evolution of another male foreleg modification, the sex brush, found in the distantly related Drosophila immigrans species group. Similar to the sex comb, we find that the origin of the sex brush correlates with novel, spatially restricted expression of the doublesex (dsx) transcription factor, the primary effector of the Drosophila sex determination pathway. The diversity of Dsx expression patterns in the immigrans species group closely reflects the differences in the presence, position, and size of the sex brush. Together with previous work on sex comb evolution, these observations suggest that tissue-specific activation of dsx expression may be a common mechanism responsible for the evolution of sexual dimorphism and particularly for the origin of novel male-specific ornaments.

Vertically transmitted rhabdoviruses are found across three insect families and have dynamic interactions with their hosts.

A small number of free-living viruses have been found to be obligately vertically transmitted, but it remains uncertain how widespread vertically transmitted viruses are and how quickly they can spread through host populations. Recent metagenomic studies have found several insects to be infected with sigma viruses (Rhabdoviridae). Here, we report that sigma viruses that infect Mediterranean fruit flies (Ceratitis capitata), Drosophila immigrans, and speckled wood butterflies (Pararge aegeria) are all vertically transmitted. We find patterns of vertical transmission that are consistent with those seen in Drosophila sigma viruses, with high rates of maternal transmission, and lower rates of paternal transmission. This mode of transmission allows them to spread rapidly in populations, and using viral sequence data we found the viruses in D. immigrans and C. capitata had both recently swept through host populations. The viruses were common in nature, with mean prevalences of 12% in C. capitata, 38% in D. immigrans and 74% in P. aegeria. We conclude that vertically transmitted rhabdoviruses may be widespread in a broad range of insect taxa, and that these viruses can have dynamic interactions with their hosts.

Concerted Evolution of the Replication-Dependent Histone Gene Family in Drosophila immigrans

The replication-dependent histone genes in Drosophila immigrans were analyzed for elucidating the evolutionary mechanism of the histone multigene family. A region of approximately 3.9 kb containing H2A-H2B-H1 genes was cloned. Six independent clones were sequenced and analyzed for nucleotide variability. The average nucleotide sequence identity in the region among repetitive copies was more than 99%, indicating that the histone multigene family in D. immigrans has evolved in a concerted fashion and with a similar level as in D. melanogaster. Amino acid variants were found at a low frequency. Analysis of the GC content at the 3rd codon position of histone genes revealed that a change in GC content, i.e., a decrease, observed in D. hydei and D. americana has occurred after the divergence of an ancestor of these two species from D. immigrans.

Cold and desiccation stress induced changes in the accumulation and utilization of proline and trehalose in seasonal populations of Drosophila immigrans

Changes in the levels of energy metabolites can limit survival ability of Drosophila species under stressful conditions but this aspect has received less attention in wild populations collected in different seasons. We tested cold or desiccation triggered changes in the accumulation or utilization of two energy metabolites (trehalose and proline) in Drosophila immigrans flies reared under season specific environmental conditions. Such D.immigrans populations were subjected to different durations of cold (0°C) or desiccation stress (5% RH) or dual stress. We found stress induced effects of cold vs desiccation on the levels of trehalose as well as for proline. Different durations of cold stress led to accumulation of trehalose while desiccation stress durations revealed utilization of trehalose. In contrast, there was accumulation of proline under desiccation and utilization of proline with cold stress. Since accumulation levels were higher than utilization of each energy metabolite, the effects of dual stress showed additive effect. However, there was no utilization of total body lipids under cold or desiccation stress. We observed significant season specific differences in the amount of energy metabolites but the rate of metabolism did not vary across seasons. Stress triggered changes in trehalose and proline suggest possible link between desiccation and cold tolerance. Finally, stress specific (cold or desiccation) compensatory changes in the levels of trehalose and proline suggest possible energetic homeostasis in D.immigrans living under harsh climatic conditions of montane localities.

Is Drosophila nasuta Lamb (Diptera, Drosophilidae) currently reaching the status of a cosmopolitan species?

In early March 2015, three males and two females of one unknown species of Drosophila were collected from a compost pile and some garbage cans in the west region of the city of São Paulo, state of São Paulo, Brazil. Morphologically it is easily identified by the presence of the following conspicuous features: a brownish dorsal stripe along pleura, an entirely iridescent silvery-whitish frons when seen directly from the front, and a row of cuneiform setae on anteroventral side of femur of foreleg; the former two traits being more evident in males. The species was easily reared in a modified banana-agar medium and two isofemale lines were established allowing to obtain mitotic cells showing a diploid chromosome number of 2n=8. Based both on morphological and chromosomal features, in addition to the geographical distribution, we concluded that the unknown flies belong to Drosophila nasuta Lamb, 1914, a tropical species of the nasuta subgroup of the Drosophila immigrans species group. Photomicrographs of male imagines, terminalia, mitotic and meiotic metaphase plates, as well as of female mitotic metaphase, are included.

Simpler is better: fewer non‐target insects trapped with a four‐component chemical lure vs. a chemically more complex food‐type bait for Drosophila suzukii

AbstractBaits – fermented food products – are generally attractive to many types of insects, which makes it difficult to sort through non‐target insects to monitor a pest species of interest. We test the hypothesis that a chemically simpler and more defined attractant developed for a target insect is more specific and attracts fewer non‐target insects than a chemically more complex food‐type bait. A four‐component chemical lure isolated from a food bait and optimized for the spotted wing drosophila (SWD), Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), was compared to the original wine/vinegar bait to assess the relative responses of non‐target insects. In several field experiments in Washington State, USA, it was shown that numbers of pest muscid flies, cutworm and armyworm moths, and pest yellowjackets were reduced in traps baited with the chemical lure compared to the wine/vinegar bait. In other field experiments in the states of Washington, Oregon, and New York, numbers of non‐target drosophilid flies were also reduced in traps baited with the chemical lure relative to wine/vinegar bait. In Washington, numbers of Drosophila melanogaster Meigen and Drosophila obscura Fallen species groups and Drosophila immigrans Sturtevant were reduced in the chemical lure traps, whereas in New York, D. melanogaster and D. obscura species groups, D. immigrans, Drosophila putrida Sturtevant, Drosophila simulans Sturtevant, Drosophila tripunctata Loew, and Chymomyza spp. numbers were reduced. In Oregon, this same effect was observed with the D. melanogaster species group. Taken together, these results indicate that the four‐component SWD chemical lure will be more selective for SWD compared to fermentation baits, which should reduce time and cost involved in trapping in order to monitor SWD.

Drosophila curviceps Species-Group (Diptera: Drosophilidae) from India, with Description of a New Species and Redescription of a Known Species

The Drosophila curviceps species subgroup is upgraded to a species-group independent from the Drosophila immigrans species group to which it has belonged, but its subgeneric assignment is still undetermined, i.e., incertae sedis. A new species, Drosophila teresae Pradhan & Sati, sp. nov., collected from Darjeeling and Uttarakhand in the Himalaya region, India is described, and supplementary and revised description for Drosophila mukteshwarensis Joshi et al. (Entomon (India) 30:75–84, 2005) is provided.

What Determines Host Acceptance and Suitability in Tropical AsianDrosophilaparasitoids?

For successful parasitism, parasitoid females must oviposit and the progeny must develop in individual hosts. Here, we investigated the determinants of host acceptance for oviposition and host suitability for larval development of Drosophila parasitoids from Bogor and Kota Kinabalu (≍1,800 km northeast of Bogor), Indonesia, in tropical Asia. Asobara pleuralis (Ashmead) from both localities oviposited frequently (>60%) in all of the drosophilid species tested, except the strain from Kota Kinabalu oviposited rarely (10%) in Drosophila eugracilis Bock & Wheeler. Leptopilina victoriae Nordlander from both localities only oviposited frequently (>77%) in species from the Drosophila melanogaster species group except D. eugracilis (<3.7%), whereas Leptopilina pacifica Novković & Kimura from Bogor oviposited frequently (>85%) only in species from the Drosophila immigrans species group. Thus, host acceptance appeared to be affected by host taxonomy, at least in Leptopilina species. Host suitability varied considerably, even among closely related drosophilid species, which suggests that the host suitability is at least in part independent of host taxonomy and that it has been determined via parasitoid-host coevolutionary interactions (i.e., arms race). Host acceptance did not always coincide with host suitability, i.e., parasitoids sometimes oviposited in unsuitable host species. Geographic origin strongly affected the host acceptance and suitability in the A. pleuralis-D. eugracilis parasitoid-host pair, whereas it only weakly affected the acceptability and suitability in other parasitoid-host combinations.

Patterns of molecular evolution of the germ line specification gene oskar suggest that a novel domain may contribute to functional divergence in Drosophila

In several metazoans including flies of the genus Drosophila, germ line specification occurs through the inheritance of maternally deposited cytoplasmic determinants, collectively called germ plasm. The novel insect gene oskar is at the top of the Drosophila germ line specification pathway, and also plays an important role in posterior patterning. A novel N-terminal domain of oskar (the Long Oskar domain) evolved in Drosophilids, but the role of this domain in oskar functional evolution is unknown. Trans-species transgenesis experiments have shown that oskar orthologs from different Drosophila species have functionally diverged, but the underlying selective pressures and molecular changes have not been investigated. As a first step toward understanding how Oskar function could have evolved, we applied molecular evolution analysis to oskar sequences from the completely sequenced genomes of 16 Drosophila species from the Sophophora subgenus, Drosophila virilis and Drosophila immigrans. We show that overall, this gene is subject to purifying selection, but that individual predicted structural and functional domains are subject to heterogeneous selection pressures. Specifically, two domains, the Drosophila-specific Long Osk domain and the region that interacts with the germ plasm protein Lasp, are evolving at a faster rate than other regions of oskar. Further, we provide evidence that positive selection may have acted on specific sites within these two domains on the D. virilis branch. Our domain-based analysis suggests that changes in the Long Osk and Lasp-binding domains are strong candidates for the molecular basis of functional divergence between the Oskar proteins of D. melanogaster and D. virilis. This molecular evolutionary analysis thus represents an important step towards understanding the role of an evolutionarily and developmentally critical gene in germ plasm evolution and assembly.