Variability of Wing Size and Shape in Three Populations of a Recent Brazilian Invader, Zaprionus indianus (Diptera: Drosophilidae), from Different Habitats

Zaprionus indianus (Diptera: Drosophilidae) is an African species that was introduced in Brazil near the end of the 1990’s decade. To evaluate the adaptive potential of morphological traits in natural populations of this recently introduced species, we have investigated wing size and shape variation at Rio de Janeiro populations only two years after the first record of Z. indianus in Brazil. Significant genetic differences among populations from three distinct ecological habitats were detected. The heritability and evolvability estimates show that, even with the population bottleneck that should have occurred during the invasion event, an appreciable amount of additive genetic variation for wing size and shape was retained. Our results also indicated a greater influence of environmental variation on wing size than on wing shape. The importance of quantitative genetic variability and plasticity in the successful establishment and dispersal of Z. indianus in the Brazilian territory is then discussed.     

Contrasting levels of genotype by environment interaction for life history and morphological traits in invasive populations of Zaprionus indianus (Diptera: Drosophilidae)

It has been demonstrated that phenotypic plasticity and genotype by environment interaction are important for coping with new and heterogeneous environments during invasions. Zaprionus indianus Gupta (Diptera: Drosophilidae) is an Afrotropical invasive fly species introduced to the South American continent in 1999. This species is generalist and polyphagous, since it develops and feeds in several different fruit species. These characteristics of Z. indianus suggest that phenotypic plasticity and genotype by environment interaction may be important in this species invasion process. In this sense, our aim was to investigate the role of genetic variation for phenotypic plasticity (genotype by environment interaction) in Z. indianus invasion of the South American continent. Specifically, we quantified quantitative genetic variation and genotype by environment interactions of morphological and life history traits in different developmental environments, that is, host fruits. This was done in different populations in the invasive range of Z. indianus in Argentina. Results showed that Z. indianus populations have considerable amounts of quantitative genetic variation. Also, genotype by environment interactions was detected for the different traits analyzed in response to the different developmental environments. Interestingly, the amounts and patterns of these parameters differed between populations. We interpreted these results as the existence of differences in evolutionary potential between populations that have an important role in the short‐ and long‐term success of the Z. indianus invasion process.     

Invasive and flexible: niche shift in the drosophilid <Emphasis Type="Italic">Zaprionus indianus</Emphasis> (Insecta,Diptera)

Although predictions of potential distributions of invasive species often assume niche conservatism, recent analyses suggest that niche shifts can also occur. Thus, further studies are necessary to provide a better understanding of niche dynamics and to predict geographic distribution in invaded areas. The present study investigated the niche shift hypothesis at a broad biogeographical scale, using the comprehensive distribution of the invasive species Zaprionus indianus in its native (Africa) and invaded (America and India) ranges. Z. indianus is a very successful invasive species that presents high adaptive flexibility and extreme physiological tolerance. To investigate whether Z. indianus changed its climatic niche from Africa to America and India, multivariate analyses, as well as ecological niche modeling procedures (GARP, MAXENT and Mahalanobis distances), were used. Multivariate analyses showed that the niche spaces of Z. indianus in Africa, India and the Americas were significantly different (Wilks’ λ from a Multivariate Analysis of Variance, MANOVA = 0.115; P < 0.0001). Out of 108 occurrences in America, only 11 (ca 10%) were classified, by Canonical Variate Analysis scores, as belonging to its original range in Africa, whereas only 5% of the 39 occurrences in India were classified as belonging to Z. indianus’ original range. Consensus results from MAXENT, GARP and Mahalanobis distances correctly predicted only 27% of the occurrences in India and 85% of occurrences in America. Thus, all analyses showed that Zaprionus indianus quickly expanded ranges into different environments in the invaded areas, suggesting climatic niche shifts, primarily in India.     

Allozyme variability in an invasive drosophilid,Zaprionus indianus (Diptera: Drosophilidae): comparison of a recently introduced Brazilian population with Old World populations

Colonizing species often go through genetic bottlenecks when new territories are invaded. The South American continent has been recently colonized by a generalist African drosophilid, Zaprionus indianus, which has become an agricultural pest in Brazil in the last five years. In this paper we used allozyme electrophoresis to estimate levels of genetic differentiation of Z. indianus collected from sites 4 300 km apart in Brazil. We also compared the level of polymorphism of the Brazilian populations with that found in laboratory strains from Africa and Asia, to verify if a significant decrease in gene variability has taken place during the invasion process. The populations were polymorphic for three out of the 11 loci investigated. Genetic distances and F_ST indices among Brazilian populations were small and generally non significant, suggesting a colonization from one single propagule followed by a rapid demographic expansion. Ancestral and old populations from Africa and Asia were slightly more heterozygous than those from Brazil. Compared to other drosophilids, Z. indianus appears to be characterized by a low proportion (25%) of polymorphic loci. We suggest that the propagule introduced to Brazil had a sufficient size to carry almost all the polymorphism from the (unknown) origin population, although not the precise allelic frequencies.     

From a non‐target to a target: identification of a fermentation volatile blend attractive to Zaprionus indianus

The African fig fly, Zaprionus indianus Gupta, is rapidly spreading through the New World and is a new potential pest for numerous fruit crops. Methods are needed to detect and monitor Z. indianus. A recent study shows that Z. indianus can be attracted with a mixture of wine and vinegar, but there are no chemical attractants yet identified. This fly was captured incidentally as a non‐target insect in experiments to develop chemical lures, based on wine and vinegar fermentation volatiles, for Drosophila suzukii Matsumura and Drosophila melanogaster Meigen. We then generated testable hypotheses on what combination of these volatiles was involved in Z. indianus attraction to wine and vinegar. We determined through a series of trapping experiments that the blend of ethanol, acetic acid, acetoin, isoamyl acetate, methionol and ethyl hexanoate constitutes a strong attractant for Z. indianus and accounts for its attraction to the combination of wine and vinegar. These results and findings provide the first opportunity to develop a long‐lasting and consistent chemical lure for trapping of Z. indianus. Such a lure in a suitable trap should provide a good means to document the spread of the fly and determine its seasonality and abundance in new areas and crops.     

Spermatogenesis of Zaprionus indianus and Zaprionus sepsoides (Diptera,Drosophilidae): Cytochemical,structural and ultrastructural characterization

Zaprionus indianus is a drosophilid native to the Afrotropical region that has colonized South America and exhibits a wide geographical distribution. In contrast, Z. sepsoides is restricted to certain African regions. The two species differ in the size of their testes, which are larger in Z. indianus than in Z. sepsoides. To better understand the biology and the degree of differentiation of these species, the current study evaluated spermatogenesis in males of different ages by conventional staining techniques and ultrastructural analysis. Spermatogenesis and the ultrastructure of spermatozoa were similar in the two species, and the diploid number was confirmed to be 2n = 12. A greater number of spermatozoa were observed in young Z. indianus (1–3 days old) compared to Z. sepsoides males, which showed a higher frequency of cells at the early stages of spermatogenesis. The head of the sperm was strongly marked by silver staining, lacto-acetic orcein and the Feulgen reaction; the P.A.S. reaction revealed glycogen granules in the testes of both species. Both species presented similar arrangement of microtubules (9+9+2), two mitochondrial derivatives of different size and 64 spermatozoa per bundle. Such similarity within the genus Zaprionus with other species of Drosophila, indicates that these structures are conserved in the family Drosophilidae. The differences observed the number and frequency of sperm cells in the early stages of spermatogenesis, between the young males of Z. indianus and Z. sepsoides, are features that may interfere with reproductive success and be related to the invasive potential of Z. indianus.     

Population genetics and recent colonization history of the invasive drosophilid Zaprionus indianus in Mexico and Central America

Zaprionus indianus, also known as the African fig fly, is an invasive pest of a variety of commercial and native fruit. The species was first reported in Brazil in 1999, but has established itself in much of the New World within the last 10–15 years. We used nucleotide sequences from a segment of the mitochondrial cytochrome c oxidase subunit I (COI) gene to examine haplotype relationships, population structure, and infer the colonization history of Z. indianus in Mexico and Panama. Construction of a haplotype network showed that six COI haplotypes, obtained from flies collected at six localities in Mexico and one in Panama, clustered into three distinct clades. Clade composition was generally consistent in flies from Panama to northwestern Mexico, and analysis of molecular variance indicated no significant structure among populations. Three of the six haplotypes from Mexico and Panama were identical to previously reported haplotypes from Brazil. None of the six haplotypes, however, were shared with previously reported haplotypes from potential source populations in the Old World. The results of our genetic analysis suggest that the invasion of Z. indianus into Central America and Mexico most probably includes a northward migration of individuals from Brazil, with the possibility of at least one additional introduction of Z. indianus to the New World. Additional sequence data from potential source populations in the Old World will be required to confidently determine the number of introductions of Z. indianus into the New World, and to identify the geographic source.     

Long‐term panmixia in a cosmopolitan Indo‐Pacific coral reef fish and a nebulous genetic boundary with its broadly sympatric sister species

Phylogeographical studies have shown that some shallow‐water marine organisms, such as certain coral reef fishes, lack spatial population structure at oceanic scales, despite vast distances of pelagic habitat between reefs and other dispersal barriers. However, whether these dispersive widespread taxa constitute long‐term panmictic populations across their species ranges remains unknown. Conventional phylogeographical inferences frequently fail to distinguish between long‐term panmixia and metapopulations connected by gene flow. Moreover, marine organisms have notoriously large effective population sizes that confound population structure detection. Therefore, at what spatial scale marine populations experience independent evolutionary trajectories and ultimately species divergence is still unclear. Here, we present a phylogeographical study of a cosmopolitan Indo‐Pacific coral reef fish Naso hexacanthus and its sister species Naso caesius, using two mtDNA and two nDNA markers. The purpose of this study was two‐fold: first, to test for broad‐scale panmixia in N. hexacanthus by fitting the data to various phylogeographical models within a Bayesian statistical framework, and second, to explore patterns of genetic divergence between the two broadly sympatric species. We report that N. hexacanthus shows little population structure across the Indo‐Pacific and a range‐wide, long‐term panmictic population model best fit the data. Hence, this species presently comprises a single evolutionary unit across much of the tropical Indian and Pacific Oceans. Naso hexacanthus and N. caesius were not reciprocally monophyletic in the mtDNA markers but showed varying degrees of population level divergence in the two nuclear introns. Overall, patterns are consistent with secondary introgression following a period of isolation, which may be attributed to oceanographic conditions of the mid to late Pleistocene, when these two species appear to have diverged.     

Differences in larval nutritional requirements and female oviposition preference reflect the order of fruit colonization of Zaprionus indianus and Drosophila simulans

Species coexist using the same nutritional resource by partitioning it either in space or time, but few studies explore how species-specific nutritional requirements allow partitioning. Zaprionus indianus and Drosophila simulans co-exist in figs by invading the fruit at different stages; Z. indianus colonizes ripe figs, whereas D. simulans oviposits in decaying fruit. Larvae feed on yeast growing on the fruit, which serves as their primary protein source. Because yeast populations increase as fruit decays, we find that ripe fruit has lower protein content than rotting fruit. Therefore, we hypothesized that Z. indianus and D. simulans larvae differ in their dietary requirements for protein. We used nutritional geometry to assess the effects of protein and carbohydrate concentration in the larval diet on life history characters in both species. Survival, development time, and ovariole number respond differently to the composition of the larval diet, with Z. indianus generally performing better across a wider range of protein concentrations. Correspondingly, we found that Z. indianus females preferred to lay eggs on low protein foods, while D. simulans females chose higher protein foods for oviposition when competing with Z. indianus. We propose the different nutritional requirements and oviposition preference of these two species allows them to temporally partition their habitat.     

Newly invading species exploiting native host-plants: the case of the African Zaprionus indianus (Gupta) in the Brazilian Cerrado (Diptera,Drosophilidae)

The African Zaprionus indianus (Diptera, Drosophilidae) was introduced into the Neotropical Region by the end of the 1990’s, and it became abundant in several types of altered and natural environments. In the Cerrado, the second South American biome in extension, it has been found mainly in open vegetation and during the rainy season. In the current work, we showed that Z. indianus utilizes a major native fruit of the Brazilian Cerrado (Solanum lycocarpum) primarily, all over the fructification period and states of fruit’s decay, confirming the adaptative versatility of this invading fly in new environments.     

Geographical Clines for Quantitative Traits in Natural Populations of a Tropical Drosophilid: Zaprionus Indianus

We analyzed natural populations of Zaprionus indianusin 10 Indian localities along a south-north transect (latitude: 10–31°3 N). Size traits (body weight, wing length and thorax length) as well as a reproductive trait (ovariole number) followed a pattern of clinal variation, that is, trait value increased with latitude. Wing/thorax ratio, which is inversely related to wing loading, also had a positive, but non-significant correlation with latitude. By contrast, bristle numbers (sternopleural and abdominal) exhibited a non-significant but negative correlation with latitude. Sex dimorphism, estimated as the female/male ratio, was very low in Z. indianus, contrasting with results already published in other species. Genetic variations among populations were also analyzed according to other geographic parameters (altitude and longitude) and to climatic conditions from each locality. A significant effect of altitude was found for size traits. For abdominal bristles, a multiple regression technique evidenced a significant effect of both latitude and altitude, but in opposite directions. Genetic variations were also correlated to climate, and mainly with average year temperature. Taking seasonal variations into account failed however to improve the predictability of morphometrical variations. The geographic differentiation of Z.indianusfor quantitative traits suggests adaptive response to local conditions, especially to temperature, but also reveals a complex situation according to traits investigated and to environmental parameters, which does not match results on other drosophilid species.     

hosimary: a new hAT transposon group involved in horizontal transfer

A PCR screening approach was used to search for sequences homologous to a previously described hAT transposon found in Drosophila simulans and Drosophila sechellia, named here as hosimary. In this study, 52 Drosophilidae species were analyzed and these sequences seem to be restricted to some species of the melanogaster group and Zaprionus indianus. These species present variable number of copies and most of those appear to be putatively encoding. The high hosimary sequences similarity among different species and the patchy distribution presented by this transposon strongly support the hypothesis that hosimary was horizontally transferred between the melanogaster group species and Z. indianus.     

One- and two-dimensional polyacrylamide gel analysis of the heat shock proteins of the virilis group of Drosophila

The heat shock proteins of the virilis group of Drosophila are analyzed by one- and two-dimensional polyacrylamide gel analysis. This group consists of the two closely related but distinct virilis and montana phylads. The analysis reveals that some of the heat shock proteins are highly conserved among the two phylads while others are not. The 83-, 72-, and 69-kdalton proteins comigrate in all species examined. There is, however, a noticable trend toward greater molecular weight variability in the smaller heat shock proteins. In general, the heat shock protein patterns within each phylad follow the proposed phylogenetic relationships with some exceptions. D. ezoana and D. littoralis, both members of the montana phylad, exhibit heat shock protein patterns more similar to those of the virilis phylad. The data also demonstrate that the montana phylad has almost two times the heat shock allele members that the virilis phylad has. It is also shown that F₁ and F₂ hybrid flies of crosses between Drosophila species having different patterns of heat shock proteins show Mendelian segregation of alleles. After several generations of inbred growth, however, the pattern of heat shock protein synthesis in reciprocal hybrids each resembles that of the paternal parent. The implications of these findings are discussed.This research was supported in part by Damon Runyon-Walter Winchell Grant DRG-233F to R.M.S. and NIH Grant GM 27611 to R.V.S. R.V.S. is the recipient of an NIH Research Career Development Award.     

Cytogenetics of the parthenogenetic grasshopper Warramaba virgo and its bisexual relatives

A study of the chromosomal location and genomic organization of the ribosomal RNA cistrons in the genus Warramaba, involving in situ hybridization and restriction enzyme analysis as well as C- and N-banding and silver staining, has confirmed that the parthenogenetic species W. virgo has two phylads. These phylads appear to have originated independently by hybridization between the precursors of the present day bisexual species P169 and P196. The clones of the Standard phylad of W. virgo have their 18S+26S rDNA cistrons located in C-bands 4, 44 and 49, while those of the Boulder-Zanthus phylad have them in C-bands 50, 74 and 87.5. The relative numbers of the ribosomal genes at the different sites vary greatly from clone to clone and are closely correlated with the width of the corresponding C- and N-bands. Site 49 of the ribosomal cistrons is present as a separate band in the eastern race A of P196 but has been incorporated into band 50 in the western race B of this species. The former race is assumed to be ancestral to the Standard phylad of W. virgo, the latter to the Boulder-Zanthus phylad, but there has been loss of the 74 and 87.5 sites in the the Standard phylad and the 4 and 44 sites in the Boulder-Zanthus clones. The ribosomal cistrons in W. picta, a species with a primitive karyotype, occur in several sites, only some of which have counterparts in P169 and P196. The 5S rDNA cistrons are located in bands 59.5, 69 and 72.5 in the Standard phylad of W. virgo. — The genomic organization of the 18S+26S rDNA cistrons, as shown by restriction enzyme analysis, is different in the two W. virgo phylads and there are also differences in organization between P196A and P196B. The pattern in P196B and that in the Boulder-Zanthus phylad suggest that they are related. As in the in situ analyses, the genomic organizations of the ribosomal cistrons in both W. virgo phylads are not simply the additive products of those in any known populations of P169 and P196. New repeat lengths indicative of segmental amplification events occur in particular clones of W. virgo. — Throughout the genus Warramaba the N-banding technique stains all bands containing 18S+26S and 5S rDNA cistrons. The Olert silver technique stains band 72.5 in the Standard phylad, but does not correlate with the locations of 18S+26S ribosomal genes.     

Phylogeography of two cryptic species of African desert jerboas (Dipodidae: Jaculus)

The lesser Egyptian jerboa Jaculus jaculus is a desert dwelling rodent that inhabits a broad Arabian–Saharan arid zone. Recently, two distant sympatric lineages were described in North‐West Africa, based on morphometric and molecular data, which may correspond to two cryptic species. In the current study, phylogenetic relationships and phylogeographical structure among those lineages and geographical populations from North Africa and the Middle East were investigated. The phylogeographical patterns and genetic diversity of the cytochrome b gene (1110 bp) were addressed on 111 jerboas from 41 localities. We found that the variation in Africa is partitioned into two divergent mitochondrial clades (10.5% divergence relating to 1.65–4.92 Mya) that corresponds to the two cryptic species: J. jaculus and J. deserti. Diversifications within those cryptic species/clades were dated to 0.23–1.13 Mya, suggesting that the Middle Pleistocene climatic change and its environmental consequences affected the evolutionary history of African jerboas. The third distant clade detected, found in the Middle East region, most likely represents a distinct evolutionary unit, independent of the two African lineages. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ??, ??–??.     

Whole genome sequence resource of Indian Zaprionus indianus

This article documents the whole genome sequence information of the Indian Zaprionus indianus, a member of the fruit fly family Drosophilidae. The sequences were generated on an Illumina platform and reads and whole genome sequence submitted to NCBI to the SRA and BioProject databases, respectively. This is the first Indian Z. indianus whole genome (draft) submitted to the sequence repository with SRA reads. The details of methodology, assembly statistics and functional annotation are presented in this work.     

Mitochondrial DNA phylogeny and the reconstruction of the population history of a species: the case of the European anchovy (Engraulis encrasicolus)

Analysis of mitochondrial DNA restriction fragment length polymorphism in European anchovy (Engraulis encrasicolus) revealed a large number of mitotypes that form two distinct clusters (phylads). Phylad A consists of one common mitotype and many rare secondary mitotypes that are one mutational step removed from the main type. Nucleotide diversity and number of homoplasious changes are low. Phylad B has a complex pattern of mitotype connectedness, high nucleotide diversity, and a large number of homoplasious changes. It is suggested that the two phylads evolved in isolation from each other and that present coexistence is the result of a secondary contact. Moreover, phylad A has a "star" phylogeny, which suggests that it has evolved in a population that experienced a drastic bottleneck followed by an explosion of size. Phylad A is practically the only phylad present in the Black Sea, with its frequency dropping to 85% in the northern Aegean, and to 40% in the rest of Mediterranean and the Bay of Biscay. The Black Sea is, therefore, the most likely place of origin of phylad A. Molecular data are consistent with a population bottleneck in the Black Sea during the last glaciation event and a subsequent exit of phylad A with the outflow into the Aegean following the ice melting. Phylogenetic analysis of anchovy mtDNA provides a reconstruction of population history in the Mediterranean, which is consistent with the geological information.      

Comparison of overwintering survival and fertility of Zaprionus indianus (Diptera: Drosophilidae) flies from native and invaded ranges

Zaprionus indianus is a fly species native to the Afrotropical biogeographic region that invaded the South American continent 20 years ago. Its southernmost record is 34°S in areas with temperate climates with cold winters. To better understand its invasion biology, we investigated physiological responses to winter-like abiotic conditions that may be relevant in Z. indianus geographic expansion. We characterized Z. indianus females reproductive traits (ovarian maturation and fertility) and survival in response to cold treatments with summer-like and winter-like photoperiods. We also compared these traits between native (Yokadouma, Africa) and invasive (Yuto, South America) range wild-derived flies. We showed that Z. indianus females have the ability to arrest ovarian maturation and maintain fertility following recovery from cold stress. The critical temperature for ovarian maturation of this species was estimated at c. 13 °C, an intermediate value between those of tropical and temperate drosophilid species. Wild-derived females from Yuto responded to winter-like photoperiod by slowing down ovarian maturation at low but permissive temperatures of 14 °C and 16 °C and also delayed the start of oviposition after cold treatment. Yuto flies also survived better and recovered 20% faster from chill coma than flies from Yokadouma. These results are consistent with a scenario of local adaptations or phenotypic plasticity in the invaded range, and suggest that photoperiod could act as modulator of ovarian arrest. Conversely, the fact that native range flies showed higher fertility after cold recovery than females from invaded range is not indicative of local adaptation. All in all, our findings report a set of physiological responses that would enable Z. indianus expansion to temperate and cold areas, but also results that are compatible with a limitation to the invasion process.     

Scenario of the spread of the invasive species Zaprionus indianus Gupta, 1970 (Diptera, Drosophilidae) in Brazil

Zaprionus indianus was first recorded in Brazil in 1999 and rapidly spread throughout the country. We have obtained data on esterase loci polymorphisms (Est2 and Est3), and analyzed them, using Landscape Shape Interpolation and the Monmonier Maximum Difference Algorithm to discover how regional invasion occurred. Hence, it was apparent that Z. indianus, after first arriving in São Paulo state, spread throughout the country, probably together with the transportation of commercial fruits by way of the two main Brazilian freeways, BR 153, to the south and the surrounding countryside, and the BR 116 along the coast and throughout the north-east.