Drosophilid Assemblages Research Articles

Host Preferences Shown by Drosophilids (Diptera) in a Commercial Fruit and Vegetable Distribution Center Follow the Wild Neotropical Pattern.

Although drosophilids have been extensively studied in laboratories worldwide, their ecology is still relatively poorly understood. This is unfortunate because some species are currently expanding their geographic distribution and infesting fruit crops. Here, we investigated the relationship between drosophilids and potential plant hosts in a commercial fruit and vegetable distribution center in the Neotropical region. We collected discarded fruits and vegetables from this commercial center during two time periods (2007-2008 and 2017-2018). Resources were weighted and individually monitored in the laboratory. The drosophilids that emerged were identified, and the relationship between them and their resources was explored. From the 99,478 kg of potential hosts collected, we identified 48 plant taxa, from which 48,894 drosophilids of 16 species emerged. On both collecting occasions, drosophilid assemblages were strongly dominated by basically the same exotic species, which explore a broader range of resources, especially those of exotic origin, when compared to neotropical drosophilids. These results are concerning because the studied site, Along with other urban markets around the world, might be acting as sources of generalist widespread species that disperse to surrounding natural vegetation and contribute to biotic homogenization.

Assemblage of drosophilids (Diptera, Drosophilidae) inhabiting flooded and nonflooded areas in the extreme South of Brazil

Several studies on the potential use of drosophilid assemblages as bioindicator systems have been carried out in the last years. Nevertheless, the successful application of these organisms in these systems requires adequate filling of several knowledge gaps. In this sense, little is known about drosophilid assemblages in wetlands and flooded areas. The present study provides the first survey of drosophilid species inhabiting such environments in the extreme South of Brazil and compares general beta-diversity patterns between assemblages of flooded versus nonflooded areas. The specimens were collected with banana-baited traps, and the assemblages recovered in eight wetlands of the southernmost coast of Brazil were compared to those recovered from seven nonflooded areas of the Pampa and Atlantic Forest biomes. A total of 5028 and 2571 individuals encompassing 27 and 37 species were collected in the flooded and nonflooded areas, respectively. The differential species composition patterns presented between these areas was statistically supported, which seems to be related to the lower beta-diversity presented by swamps, especially in regard to dominance patterns. So, the open and climatically harsher environment provided by wetlands possibly constitutes a hostile environment for the entry and, mainly, for the persistence of several native Drosophilidae species, in contrast to some exotic and more plastic species (as Drosophila simulans and Zaprionus indianus). Since the diversity gradient of flooded areas does not seem to be related to the conservation status of the swamp, our results question the use of Drosophilidae species as bioindicators of environmental disturbance and antropic influence in wetlands.

Measuring the variability of the drosophilid assemblages associated with forests of the Brazilian savanna across temporal and spatial scales

The relevant scales over which specific communities vary must be identified to address fundamental ecological questions and to advance the conservation of biological diversity. In this study, the variation among drosophilid assemblages associated with forests was quantified at a large temporal–spatial scale. Our results are based on data collected in four conservation units (CUs) in the Brazilian savanna across four seasons and two years. The primary component of variation occurred at the temporal scale: it was three times greater than that of the spatial scale. Significant variability was also found in the interaction between seasons and CUs. Measuring the temporal and spatial variability of drosophilid diversity in forests contributed to the improvement of the methodological framework supporting such assemblages as bioindicators and provided important insights into the mechanisms behind the dynamic patterns in time and space that ultimately can improve our understanding of Cerrado biodiversity.

Environmental determinants on the assemblage structure of Drosophilidae flies in a temperate-subtropical region.

The species composition and the relative abundance of species in an insect community can vary in time and space for many reasons, including climatic variables and habitat preferences. Drosophilids were collected each quarter from April 2011 to April 2012 (five collections in all) in a natural area of the Pampa biome, considering three environments: open field, forest edge and the interior of forest patches. Kruskal-Wallis and chi-square tests were used to examine the effects of temporal and spatial components on the drosophilid assemblage. Four diversity measures: S obs , S rar , H' and E var were used to evaluate the community structure. A total of 7164 drosophilids belonging to 51 species were collected. The interaction of species in each environment varied among sampling periods. The abundance of both Neotropical and exotic species was affected by temporal and spatial components. The species of the D. repleta group were predominantly more abundant in the open field, but they migrated to the forest patches during periods of thermal stress. Generally, diversity was greatest in the interior of forest patches. Nevertheless, temporal components appear to be the predominant environmental determinant of the characteristics of the drosophilid community of the Pampas. Furthermore, the forest patches appear to act as a center of recolonization, reinforcing their importance in the maintenance of biodiversity in the Pampas; this function will be even more important in the future, when the temperatures will, most likely, be higher.

Spatial and temporal dynamics of drosophilid larval assemblages associated to fruits

The study of organisms and their resources is critical to further understanding population dynamics in space and time. Although drosophilids have been widely used as biological models, their relationship with breeding and feeding sites has received little attention. Here, we investigate drosophilids breeding in fruits in the Brazilian Savanna, in two contrasting vegetation types, throughout 16 months. Specifically, larval assemblages were compared between savannas and forests, as well as between rainy and dry seasons. The relationships between resource availability and drosophilid abundance and richness were also tested. The community (4,022 drosophilids of 23 species and 2,496 fruits of 57 plant taxa) varied widely in space and time. Drosophilid assemblages experienced a strong bottleneck during the dry season, decreasing to only 0.5% of the abundance of the rainy season. Additionally, savannas displayed lower richness and higher abundance than the forests, and were dominated by exotic species. Both differences in larval assemblages throughout the year and between savannas and gallery forests are consistent with those previously seen in adults. Although the causes of this dynamic are clearly multifactorial, resource availability (richness and abundance of rotten fruits) was a good predictor of the fly assemblage structure.

Drosophilid Species (Diptera) in the Brazilian Savanna are Larger in the Dry Season

Abstract Recently, interest in the effects of global climate change on biological communities has grown substantially. Both historical records and model predictions indicate that temperatures and aridity will likely increase in the continental interiors, although the effects of increased aridity have been less studied. The Brazilian savanna has a strong annual dry season, during which time drosophilid populations experience bottlenecks. In this study, we monitored a drosophilid assemblage in the core area of the Brazilian savanna throughout 1 yr. We then compared fly wings collected in the dry and rainy seasons for two common drosophilid species, Drosophila mercatorum Patterson & Wheeler and Drosophila simulans Sturtevant. Drosophilid abundance and richness decreased significantly in the dry season, confirming previous findings. In addition, although no significant differences in wing shape were observed for flies collected during the two seasons, the wing size of both focal species was significantly higher in the dry season. Considering the reported association between Drosophila Fallén wing size and body size, we deduced that the flies were larger in the dry season. D. mercatorum and D. simulans were also found at higher relative abundances in the dry season, when most species were not collected in the field. The observed difference in wing size could have been the result of biotic or abiotic factors, such as larval density and climate. More efforts are necessary to untangle the factors that lie behind this pattern, but it is possible that increased size is an advantageous trait when struggling against dry conditions.

The relative roles of habitat heterogeneity and disturbance in drosophilid assemblages (Diptera,Drosophilidae) in theCerrado

AbstractThe Brazilian Cerrado, a vegetation mosaic considered to be a unique savannah hotspot, contains a great diversity of insects. It is uncertain how communities of insects in the Cerrado respond, at local scale, to the strong heterogeneity of the biome or to the increasing levels of anthropogenic disturbance.This study examines the relative importance of habitat heterogeneity and human disturbance for the structure of drosophilid assemblages in this biome.Our results are based on standardised monthly sampling at 25 sites (3 conserved forests, 4 disturbed forests, 8 conserved savannahs, and 10 disturbed savannahs) throughout 1 year.The assemblage compositions differed across habitats. The conserved forests had a singular drosophilid assemblage characterised by typical narrow‐ranging neotropical species. Assemblages from savannahs and disturbed forests contained more exotic species than those from conserved forests. The assemblages of disturbed forests were more similar to those of the savannahs than to those of the conserved forests. Savannah assemblages did not differ from each other; these assemblages shared a great number of both exotic and neotropical species widespread in neotropical regions.At the reserve scale, the strong natural heterogeneity of the Cerrado is the primary factor impacting the structure of drosophilid assemblages. Nevertheless, disturbance explained the differences in assemblage structure between the conserved and disturbed forests. Even low disturbance levels in forests could cause a decrease in heterogeneity and begin to impoverish these environments, leading to the biotic homogenisation of this currently rich biome.

Temporal and vertical drosophilid (Insecta; Diptera) assemblage fluctuations in a neotropical gallery forest

The drosophilids of a gallery forest in the Brazilian savanna were investigated to identify the temporal and vertical patterns in the community structure of these insects. Twelve monthly collections were performed (December 2007 to November 2008) in three vertical strata of the forest (0, 4 and 8 m heights) using 30 traps baited with fermented banana. The drosophilid assemblage was composed of 61 species (7,623 individuals), experienced temporal fluctuations and was vertically stratified. Both the diversity and abundance of the flies were very low during the dry season, a time when the assemblages were dominated by the exotic species Drosophila simulans, whereas the community showed an increased abundance and richness of neotropical species and showed vertical stratification in the wet season. Rare species were found primarily at the ground level (flies usually associated with neotropical forests) or in the canopy, which harbors species currently associated with open vegetation, little-studied neotropical species and most likely several new species. These changes, which reflect drosophilid adaptations to different environments, involve a shifting of the ecological niches occupied by the flies in the forest over time. This process of change is termed niche construction. Thus, we conclude that this complex and dynamic community structure, which is related to the interaction of several environmental factors associated with different forest environments, contributes to the high diversity of gallery forests in the Brazilian savanna.

High Abundance of Neotropical Drosophilids (Diptera: Drosophilidae) in Four Cultivated Areas of Central Brazil

The drosophilid assemblages of four cultivated areas (soy, bean, corn, and orange plantations) grown in the core of the Neotropical region were analyzed by comparing their abundances and compositions. The collections, which were gathered using 38 banana traps, captured 12,560 drosophilids, including nine Neotropical and six exotic species. Most of the flies were collected in the bean (43%) and soy (42%) fields. The composition and relative abundance of species also varied among cultivated areas, with orange orchards presenting the highest relative abundance of exotics due to the dominance of the Afrotropical Zaprionus indianus (Gupta). Crop plantations were dominated by a Neotropical species, Drosophila cardini (Sturtevant), which has been shown to be well adapted to dry and disturbed environments. We discuss the drosophilid assemblages of the cultivated areas, comparing them with assemblages from neighbor urban and natural environments. The low drosophilid richness found in this study is similar to the richness found in urban environments and lower than the drosophilid richness of forests, supporting a pattern already known for other taxa. The high abundance of drosophilids in cultivated areas, as well as the dominance of a Neotropical species (D. cardini) in the crop assemblages, was a surprising result.

Drosophilid Assemblages at Different Urbanization Levels in the City of Porto Alegre, State of Rio Grande do Sul, Southern Brazil

The present study analyzed the drosophilid assemblages in different levels of urbanization in the city of Porto Alegre, Rio Grande do Sul, Brazil. Collections were carried out in 2008 in three different environments: a highly urbanized area-"Jardim Botânico," a forested area with intermediary urbanization-"Parque Gabriel Knijnik," and in a relatively well-preserved forested area, although threatened by the urban growth-"Morro Santana." In Jardim Botânico, 36 species belonging to four genera were found, with high abundance of exotic species as Drosophila simulans Sturtevant and Zaprionus indianus (Gupta). In Parque Gabriel Knijnik, 33 species that belonged to four genera were found, with higher abundances of native species belonging to the Drosophila tripunctata species group and Drosophila willistoni species subgroup, and lower abundance of exotic species. As for Morro Santana, 32 species and three genera were found, with higher abundances of native groups, low representativeness of exotic species, and absence of Zaprionus indianus. The analysis of the Jaccard index showed higher similarity in the species composition between samples collected in summer and autumn, and between samples collected in winter and spring. On the other hand, the Morisita index differentiated Jardim Botânico from the other two studied sites. Our results show that Morro Santana is an important area of native biodiversity, reinforcing, therefore, the inclusion of this area in the project for the creation of an ecological corridor as proposed by the Ministry of the Environment of Brazil.

Biological Invasions in the Amazonian Tropical Rain Forest: The Case of Drosophilidae (Insecta, Diptera) in Ecuador, South America

ABSTRACTThere have been few reports of invasions in continental rain forests, especially for exotic animals. This study provides original data concerning the potential of exotic drosophilid species to colonize the Amazonian tropical rain forest. To investigate if the structure of drosophilid assemblages differed in response to anthropogenic disturbance, we performed a taxonomic survey at six sites within the Yasuni National Park in Ecuadorian Amazonia along a disturbance gradient from pristine to clearcut artificial forest. A total of 7425 individuals from 34 species were collected of which seven species were exotic. There was significant variation in the assemblage composition along this disturbance gradient; 31 percent of which was explained by the presence of exotic species, particularly at the most disturbed sites, through nonmetric multidimensional scaling and SIMPER analyses. These results confirm the susceptibility of continental rain forests to invasion by exotic species. There is an urgent need to develop and implement monitoring systems, for example, based on drosophilid assemblage surveys, to detect exotic invasions in continental tropical forests.

Seasonal dynamics of a drosophilid (Diptera) assemblage and its potencial as bioindicator in open environments

Drosophila Fallen, 1823 (Diptera, Drosophilidae) is for long a well-established model organism for genetics and evolutionary research. The ecology of these flies, however, has only recently been better studied. Recent papers show that Drosophila assemblies can be used as bioindicators of forested environment degradation. In this work the bioindicator potential of drosophilids was evaluated in a naturally opened environment, a coastal strand-forest (restinga). Data from nine consecutive seasonal collections revealed strong temporal fluctuation pattern of the majority of Drosophila species groups. Drosophila willistoni group was more abundant at autumns, whereas D. cardini and D. tripunctata groups were, respectively, expressive at winters and springs, and D. repleta group at both seasons. The exotic species D. simulans Sturtevant, 1919 (from D. melanogaster group) and Zaprionus indianus Gupta, 1970 were most abundant at summers. Overall, the assemblage structure did not show the same characteristics of forested or urban environments, but was similar to the forests at winters and to cities at summers. This raises the question that this locality may already been under urbanization impact. Also, this can be interpreted as an easily invaded site for exotic species, what might lead to biotic homogenization and therefore can put in check the usage of drosophilid assemblages as bioindicators at open environments.

Drosophilids (Insecta, Diptera) as Tools for Conservation Biology

We advocate the use of drosophilid flies as biological models on biological conservation by presenting a case study in the Cerrado at landscape scale. We analyzed the drosophilid assemblage in the Parana Valley, together with a baseline data from Federal District. We found four different drosophilid assemblages structured in both local and regional scales. Our study confirms the importance of the Parana Valley as a diversity center, and the urgency in creating reserves in the region to protect its biological uniqueness. Analyzing drosophilid assemblage composition could help for understanding Cerrado biodiversity by perceiving and focusing it in different scales, and therefore, helping for more accurate and efficient reserve selection, design and placement. Drosophilids can be very useful to study the patterns and processes related to biodiversity and also how human activities affect it, permitting the elaboration of efficient conservation strategies, and improving projections about what might happen in the future.

The drosophilid fauna (Diptera, Drosophilidae) of the transition between the Pampa and Atlantic Forest Biomes in the state of Rio Grande do Sul, southern Brazil: first records

Although studies on drosophilid (Diptera, Drosophilidae) assemblages have become relatively abundant in the past decades, many environments remain to be searched. The present study investigates the composition, the species abundances and the richness of the drosophilid assemblages in two localities of the municipality of Cruz Alta, northwestern region of the state of Rio Grande do Sul, a point of contact between the biomes Atlantic Forest and Pampa: (i) an urban area (2007), constituted by a domestic orchard with Citrus trees, and (ii) a forested area, in Centro de Educação, Pesquisa e Proteção Ambiental - CEPPA (2008/2009), of Universidade de Cruz Alta, located in a fragment of riparian forest. Collections were conducted using fermented banana-baited traps and repeated periodically. A total of 7,428 individuals were caught, belonging to two subfamilies, six genera and 53 species. In the urban area, 22 species were found, from two genera (N = 2,421), while in the forested area 46 species were found, from six genera (N = 5,007). Six exotic species were found, markedly more abundant in the urban area, where they corresponded to 95% of the specimens, in comparison to 50% in the forest. Between the Neotropical species, the most common were Drosophila maculifrons Duda and D. polymorpha Dobzhansky & Pavan. Only D. simulans Sturtevant was captured in all samples in both localities. The present survey represents the first records for the state of Rio Grande do Sul of the D. canalinea and D. virilis species groups and the species D. arassari Cunha & Frota-Pessoa, D. fuscolineata Duda, D. nigricruria Patterson & Mainland, D. papei Bächli & Vilela, D. senei Vilela, D. trifilum Frota-Pessoa, D. virilis Sturtevant, Leucophenga maculosa (Coquillett) and Rhinoleucophenga obesa (Loew). Furthermore, it also represents the first record for the state of the genera Amiota Loew, Leucophenga Mik and Rhinoleucophenga Hendel and of the subfamily Steganinae. So, the present survey raises the number of drosophilid species recorded for the state from 66 to 75, the number of genera from five to eight, and subfamilies from one to two.

Temporal Dynamics and Resource Availability for Drosophilid Fruit Flies (Insecta, Diptera) in a Gallery Forest in the Brazilian Savanna

Seasonality can cause severe bottlenecks in natural populations, even leading to local extinction. Large variation in resource availability may explain the bottlenecks, but the role of these variations is still poorly understood. The goal of this study was to analyze if temporal variations in the guild of drosophilids breeding in fruits ofMauritia flexuosa(Arecaceae) can be explained by the shortage of this resource during the dry season. Fruits ofM. flexuosawere collected over one year in a gallery forest located in the Central Brazilian Savanna. The drosophilid assemblage varied over time, with a lower density of species and of individuals in the dry season, when the percentage of colonized fruits was also smaller. These findings suggest that although the fruits were available during the dry season, they were underused. This way, the resource availability does not seem to regulate the community in the dry season.

Drosophilid assemblages as a bioindicator system of human disturbance in the Brazilian Savanna

According to the Convention on Biological Diversity (CBD) the development of bioindicators is extremely necessary to achieve the conservation targets by 2010, and insects are considered an effective group for this goal. Drosophilids are regarded as potential indicators, although this idea remains untested. Therefore, we followed up a protocol to test the drosophilid potential indicator for human disturbance in the Brazilian Savanna, one of the richest and most threatened tropical biomes in the world. Sampling was undertaken in one urban environment and two biological reserves, representing four habitat types (undisturbed gallery forest, disturbed gallery forest, undisturbed savanna, and urban environment). We examined differences in the drosophilid assemblages among habitat types and used the Indicator Value (IndVal) method to point out the indicator species. We also tested the two-stage indicator validation, a protocol recently proposed in the literature, to validate the indicator species for undisturbed gallery forest and savannas, in independent samples. The assemblage variables varied mainly in undisturbed gallery forests, and reflected changes from an undisturbed to a disturbed stage. The IndVal associated with the two-stage protocol showed reliable characteristic species, which are very helpful for diagnostic surveys. Likewise, species that can detect changes in the habitats were also found. We found a set of indicators, which together may be very efficient for both assessing and reflecting a variety of conditions, improving the confidence of the bioindication system, expanding the taxonomic options for bioindicators, and therefore, contributing to the conservation of this region.

Drosophilids (Diptera) from an Atlantic Forest Area in Santa Catarina, Southern Brazil

The present work aims at knowing the faunal composition of drosophilids in forest areas of southern Brazil. Besides, estimation of species richness for this fauna is briefly discussed. The sampling were carried out in three well-preserved areas of the Atlantic Rain Forest in the State of Santa Catarina. In this study, 136,931 specimens were captured and 96.6% of them were identified in the specific level. The observed species richness (153 species) is the largest that has been registered in faunal inventories conducted in Brazil. Sixty-three of the captured species did not fit to the available descriptions, and we believe that most of them are non-described species. The incidence-based estimators tended to give rise to the largest richness estimates while the abundance based give rise to the smallest ones. Such estimators suggest the presence from 172.28 to 220.65 species in the studied area. Based on these values, from 69.35 to 88.81% of the expected species richness were sampled. We suggest that the large richness recorded in this study is a consequence of the large sampling effort, the capture method, recent advances in the taxonomy of drosophilids, the high preservation level and the large extension of the sampled fragment and the high complexity of the Atlantic Rain forest. Finally, our data set suggest that the employment of estimators of richness for drosophilid assemblages is useful but it requires caution.

Application of the quadratic entropy indices for diversity studies of drosophilid assemblages

Most diversity indices widely used in ecology (e.g. the Shannon-Wiener index and the Gini-Simpson index) do not reflect taxonomic or other differences among species. Quadratic entropy, proposed by C.R. Rao (1982), takes these differences into account. The aim of this paper is to demonstrate the application of this diversity index in investigations of drosophilid species diversity. Quadratic entropy and Simpson index values are also compared. The elements of the difference matrix in the quadratic form are taxonomic differences (distances) among the species. The difference is defined by the position of the lowest-ranking taxon containing both species. According to the results, the Gini-Simpson index and the taxonomic quadratic entropy are positively correlated. The observed differences are due to the fact that assemblages with greater taxonomic distances produce greater quadratic entropy. Drosophilid species can be assigned to specific life habit classes, more specifically to resource types. After postulating differences between the types, we used the quadratic entropy measure to analyse resource diversity. These kinds of examinations approximate to an operative association of species diversity and environmental diversity.

Randomness and aggregation: analysis of dispersion in an epiphytic chironomid community

SUMMARY1. Patterns of dispersion in a chironomid community on the submersed macrophyte Myriophyllum spicatum were analysed.2. Random dispersion commonly occurred throughout the year, with an average of 40% of all species being observed with random spatial patterns. The frequency of occasions with random dispersion varied among chironomid species, ranging from 3.3% in Rheotanytarsus curtistylus to 56% in Thienemanniella majuscula.3. Estimates of the negative binomial parameter k show that 26% of all cases demonstrate strong aggregation (0 < k < 1.0) while nearly half (47%) have quasi‐random dispersion. Interspecific variation in k was not significant statistically when all the species were considered together, although a pairwise comparison between two abundant species Tvetenia calvescens and Rheotanytarsus curtistylus demonstrated a marginally significant difference. When different instars were compared, the percentage frequency of strong aggregation (0 < k < 1.0) declined from first instars (49%) to later instars (II‐38%, III‐24% and IV‐27%).4. Variance/mean and m*—m regressions (m* is Lloyd's mean crowding statistic and m is the sample mean) both fitted the data well, but there was little indication of significant interspecific variation in parameter values, particularly the slope of regression.5. Dispersion patterns were examined along with the analysis of spatial overlap in this community. Forty‐two per cent of species‐pairs with reduced spatial overlap (spatially ‘segregated’ pairs) contained one or both species with random dispersion, while the corresponding value for spatially unsegregated pairs was 57%. This suggests that spatial segregation is not necessarily caused by strong, independent aggregation of both species. Comparing spatially segregated vs. unsegregated pairs, the former tend to have one species with a stronger tendency of aggregation than species of the latter.6. Patterns of dispersion observed were considered in the light of ‘random patch formation’. Random patch formation emphasizes the stochasticity of patch‐forming processes as well as the stochastically dynamic nature of resultant patches. Unlike terrestrial drosophilid assemblages, where strong aggregation is a predominant pattern, this chironomid community demonstrates widely varying degrees of dispersion with high occurrence of randomness, reflecting the stochasticity of dispersal and recolonization processes. It is suggested that, in terms of species coexistence, more emphasis should be placed on stochasticity rather than on aggregation in this type of community.