Transposable elements P and gypsy in natural populations of Drosophila willistoni

Chromosome mapping of retrotransposon AviRTE in a neotropical bird species: Trogon surrucura (Trogoniformes; Trogonidae)

Avian genomes are characterized as being more compact than other amniotes, with less diversity and density of transposable elements (TEs). In addition, birds usually show bimodal karyotypes, exhibiting a great variation in diploid numbers. Some species present unusually large sex chromosomes, possibly due to the accumulation of repetitive sequences. Avian retrotransposon-like element (AviRTE) is a long interspersed nuclear element (LINE) recently discovered in the genomes of birds and nematodes, and it is still poorly characterized in terms of chromosomal mapping and phylogenetic relationships. In this study, we mapped AviRTE isolated from the Trogon surrucura genome into the T. surrucura (TSU) karyotype. Furthermore, we analyzed the phylogenetic relationships of this LINE in birds and other vertebrates. Our results showed that the distribution pattern of AviRTE is not restricted to heterochromatic regions, with accumulation on the W chromosome of TSU, yet another species with an atypical sex chromosome and TE hybridization. The phylogenetic analysis of AviRTE sequences in birds agreed with the proposed phylogeny of species in most clades, and allowed the detection of this sequence in other species, expanding the distribution of the element.

Unveiling the Mycodrosophila projectans (Diptera, Drosophilidae) species complex: Insights into the evolution of three Neotropical cryptic and syntopic species

The Zygothrica genus group has been shown to be speciose, with a high number of cryptic species. DNA barcoding approaches have been a valuable tool to uncover cryptic diversity in this lineage, as recently suggested for the Neotropical Mycodrosophila projectans complex, which seems to comprise at least three different species. The aim of this study was to confirm the subdivision of the M. projectans complex while shedding some light on the patterns and processes related to its diversification. In this sense, the use of single and multi-locus datasets under phylogenetic, distance, coalescence, and diagnostic nucleotide approaches confirmed the presence of at least three species under the general morphotype previously described as M. projectans. Only a few subtle morphological differences were found for the three species in terms of aedeagus morphology and abdominal color patterns. Ecologically, sympatry and syntopy seem to be recurrent for these three cryptic species, which present widely overlapping niches, implying niche conservatism. This morphological and ecological similarity has persisted though cladogenesis within the complex, which dates back to the Miocene, providing an interesting example of morphological conservation despite ancient divergence. These results, in addition to contrasting patterns of past demographic fluctuations, allowed us to hypothesize patterns of allopatric or parapatric diversification with secondary contact in Southern Brazil. Nevertheless, genetic diversity was generally high within species, suggesting that migration may encompass an adaptive response to the restrictions imposed by the ephemerality of resources.

Interpopulation variation of transposable elements of the hAT superfamily in Drosophila willistoni (Diptera: Drosophilidae): in-situ approach

Transposable elements are abundant and dynamic part of the genome, influencing organisms in different ways through their presence or mobilization, or by acting directly on pre- and post-transcriptional regulatory regions. We compared and evaluated the presence, structure, and copy number of three hAT superfamily transposons (hobo, BuT2, and mar) in five strains of Drosophila willistoni species. These D. willistoni strains are of different geographical origins, sampled across the north-south occurrence of this species. We used sequenced clones of the hAT elements in fluorescence in-situ hybridizations in the polytene chromosomes of three strains of D. willistoni. We also analyzed the structural characteristics and number of copies of these hAT elements in the 10 currently available sequenced genomes of the willistoni group. We found that hobo, BuT2, and mar were widely distributed in D. willistoni polytene chromosomes and sequenced genomes of the willistoni group, except for mar, which is restricted to the subgroup willistoni. Furthermore, the elements hobo, BuT2, and mar have different evolutionary histories. The transposon differences among D. willistoni strains, such as variation in the number, structure, and chromosomal distribution of hAT transposons, could reflect the genomic and chromosomal plasticity of D. willistoni species in adapting to highly variable environments.

Evolutionary history and classification of Micropia retroelements in Drosophilidae species

Transposable elements (TEs) have the main role in shaping the evolution of genomes and host species, contributing to the creation of new genes and promoting rearrangements frequently associated with new regulatory networks. Support for these hypotheses frequently results from studies with model species, and Drosophila provides a great model organism to the study of TEs. Micropia belongs to the Ty3/Gypsy group of long terminal repeats (LTR) retroelements and comprises one of the least studied Drosophila transposable elements. In this study, we assessed the evolutionary history of Micropia within Drosophilidae, while trying to assist in the classification of this TE. At first, we performed searches of Micropia presence in the genome of natural populations from several species. Then, based on searches within online genomic databases, we retrieved Micropia-like sequences from the genomes of distinct Drosophilidae species. We expanded the knowledge of Micropia distribution within Drosophila species. The Micropia retroelements we detected consist of an array of divergent sequences, which we subdivided into 20 subfamilies. Even so, a patchy distribution of Micropia sequences within the Drosophilidae phylogeny could be identified, with incongruences between the species phylogeny and the Micropia phylogeny. Comparing the pairwise synonymous distance (dS) values between Micropia and three host nuclear sequences, we found several cases of unexpectedly high levels of similarity between Micropia sequences in divergent species. All these findings provide a hypothesis to the evolution of Micropia within Drosophilidae, which include several events of vertical and horizontal transposon transmission, associated with ancestral polymorphisms and recurrent Micropia sequences diversification.

Characterization of Herves-like transposable elements (hATs) in Drosophila species and their evolutionary scenario

A monophyletic group of Drosophila hAT transposable elements, referred to as Herves-like, was characterized and found to be present in 46% of 57 screened Drosophila species. A remarkable characteristic of these elements is the presence of a long array of minisatellite repeats (MnRs) in both subterminal extremities of the elements. The copy number of these minisatellites was highly variable between and within populations. Twenty-three strains of Drosophila willistoni, covering its geographic distribution, were screened for polymorphism in the copy number of 5' MnRs, showing a variation from 7 to 20 repeat copies. These MnRs are well conserved among Drosophila species and probably function as transposase binding sequences, as provided by short subterminal repeats in other hAT elements. Miniature inverted repeat transposable elements were found in 27% of species carrying Herves-like elements. Phylogenetic analysis showed incongruences between transposable elements and species phylogenies, suggesting that at least four horizontal transfer events have occurred.

The somatic mobilization of transposable element mariner-Mos1 during the Drosophila lifespan and its biological consequences

Transposable elements (TEs) are mobile DNA sequences on genomes. Some elements are able to transpose in somatic cells, a process known as somatic transposition (ST), which has been associated with detrimental biological effects. The mariner-Mos1 element of Drosophila promotes transposition in somatic and germline cells and is an excellent model for studies related to the biological consequence of somatic excision (SE). In this work, we used temperature stress to induce increasing transposition of mariner-Mos1 during different stages of the development of D. simulans, aiming to quantify SE during lifespan. Furthermore, strains of D. melanogaster exhibiting differential expression of mariner-Mos1 were employed for estimating some biological consequences of mariner mobilization. It is shown that SE of mariner-Mos1 was not constant during development; the larval phase had the highest rates while the pupal stage exhibited lower rates, and in the embryonic stage, no difference was detected. SE can be detrimental, as suggested by correlation in SE level and reduction in behavioral activities and embryonic viability. This study showed that mariner-Mos1 SE accumulates during the Drosophila life cycle, and can be involved in detrimental effects.

Evolution of DNMT2 in drosophilids: Evidence for positive and purifying selection and insights into new protein (pathways) interactions

The DNA methyltransferase 2 (DNMT2) protein is the most conserved member of the DNA methyltransferase family. Nevertheless, its substrate specificity is still controversial and elusive. The genomic role and determinants of DNA methylation are poorly understood in invertebrates, and several mechanisms and associations are suggested. In Drosophila, the only known DNMT gene is Dnmt2. Here we present our findings from a wide search for Dnmt2 homologs in 68 species of Drosophilidae. We investigated its molecular evolution, and in our phylogenetic analyses the main clades of Drosophilidae species were recovered. We tested whether the Dnmt2 has evolved neutrally or under positive selection along the subgenera Drosophila and Sophophora and investigated positive selection in relation to several physicochemical properties. Despite of a major selective constraint on Dnmt2, we detected six sites under positive selection. Regarding the DNMT2 protein, 12 sites under positive-destabilizing selection were found, which suggests a selection that favors structural and functional shifts in the protein. The search for new potential protein partners with DNMT2 revealed 15 proteins with high evolutionary rate covariation (ERC), indicating a plurality of DNMT2 functions in different pathways. These events might represent signs of molecular adaptation, with molecular peculiarities arising from the diversity of evolutionary histories experienced by drosophilids.

Combining morphology and molecular data to improve Drosophila paulistorum (Diptera, Drosophilidae) taxonomic status

The willistoni species subgroup has been the subject of several studies since the latter half of the past century and is considered a Neotropical model for evolutionary studies, given the many levels of reproductive isolation and different evolutionary stages occurring within them. Here we present for the first time a phylogenetic reconstruction combining morphological characters and molecular data obtained from 8 gene fragments (COI, COII, Cytb, Adh, Ddc, Hb, kl-3 and per). Some relationships were incongruent when comparing morphological and molecular data. Also, morphological data presented some unresolved polytomies, which could reflect the very recent divergence of the subgroup. The total evidence phylogenetic reconstruction presented well-supported relationships and summarized the results of all analyses. The diversification of the willistoni subgroup began about 7.3 Ma with the split of D. insularis while D.paulistorum complex has a much more recent diversification history, which began about 2.1 Ma and apparently has not completed the speciation process, since the average time to sister species separation is one million years, and some entities of the D. paulistorum complex diverge between 0.3 and 1 Ma. Based on the obtained data, we propose the categorization of the former "semispecies" of D. paulistorum as a subspecies and describe the subspecies D. paulistorum amazonian, D. paulistorum andeanbrazilian, D. paulistorum centroamerican, D. paulistorum interior, D. paulistorum orinocan and D. paulistorum transitional.

BuT2 is a member of the third major group of hAT transposons and is involved in horizontal transfer events in the genus Drosophila

The hAT superfamily comprises a large and diverse array of DNA transposons found in all supergroups of eukaryotes. Here we characterized the Drosophila buzzatii BuT2 element and found that it harbors a five-exon gene encoding a 643-aa putatively functional transposase. A phylogeny built with 85 hAT transposases yielded, in addition to the two major groups already described, Ac and Buster, a third one comprising 20 sequences that includes BuT2, Tip100, hAT-4_BM, and RP-hAT1. This third group is here named Tip. In addition, we studied the phylogenetic distribution and evolution of BuT2 by in silico searches and molecular approaches. Our data revealed BuT2 was, most often, vertically transmitted during the evolution of genus Drosophila being lost independently in several species. Nevertheless, we propose the occurrence of three horizontal transfer events to explain its distribution and conservation among species. Another aspect of BuT2 evolution and life cycle is the presence of short related sequences, which contain similar 5' and 3' regions, including the terminal inverted repeats. These sequences that can be considered as miniature inverted repeat transposable elements probably originated by internal deletion of complete copies and show evidences of recent mobilization.

Assessment and reconstruction of novel HSP90 genes: duplications, gains and losses in fungal and animal lineages

Hsp90s, members of the Heat Shock Protein class, protect the structure and function of proteins and play a significant task in cellular homeostasis and signal transduction. In order to determine the number of hsp90 gene copies and encoded proteins in fungal and animal lineages and through that key duplication events that this family has undergone, we collected and evaluated Hsp90 protein sequences and corresponding Expressed Sequence Tags and analyzed available genomes from various taxa. We provide evidence for duplication events affecting either single species or wider taxonomic groups. With regard to Fungi, duplicated genes have been detected in several lineages. In invertebrates, we demonstrate key duplication events in certain clades of Arthropoda and Mollusca, and a possible gene loss event in a hymenopteran family. Finally, we infer that the duplication event responsible for the two (a and b) isoforms in vertebrates occurred probably shortly after the split of Hyperoartia and Gnathostomata.

Reevaluating the infection status by the Wolbachia endosymbiont in Drosophila Neotropical species from the willistoni subgroup

Infections by the endosymbiotic bacterium Wolbachia developed a rapid global expansion within Old World Drosophila species, ultimately infecting also Neotropical species. In this sense, screenings are necessary to characterize new variants of Wolbachia or new hosts, and also in order to map the dynamics of already known infections. In this paper, we performed a double screening approach that combined Dot-blot and PCR techniques in order to reevaluate the infection status by Wolbachia in species from the willistoni subgroup of Drosophila. Genomic DNA from isofemale lines descendent from females collected in the Amazonian Rainforest (n=91) were submitted to Dot-blot, and were positive for Wolbachia, producing a gradient of hybridization signals, suggesting different infection levels, which was further confirmed through quantitative PCR. Samples with a strong signal in the Dot-blot easily amplified in the wsp-PCR, unlike most of the samples with a medium to weak signal. It was possible to molecularly characterize three Drosophila equinoxialis isofemale lines that were found to be infected in a low density by a wMel-like Wolbachia strain, which was also verified in a laboratory line of Drosophila paulistorum Amazonian. We also found Drosophila tropicalis to be infected with the wAu strain and a Drosophila paulistorum Andean-Brazilian semispecies laboratory line to be infected with a wAu-like Wolbachia. Moreover, we observed that all Drosophila willistoni samples tested with the VNTR-141 marker harbor the same Wolbachia variant, wWil, either in populations from the South or the North of Brazil. Horizontal transfer events involving species of Old World immigrants and Neotropical species of the willistoni subgroup are discussed.

Mar, a MITE family of hAT transposons in Drosophila

Background

Miniature inverted-repeat transposable elements (MITEs) are short, nonautonomous DNA elements flanked by subterminal or terminal inverted repeats (TIRs) with no coding capacity. MITEs were originally recognized as important components of plant genomes, where they can attain extremely high copy numbers, and are also found in several animal genomes, including mosquitoes, fish and humans. So far, few MITEs have been described in Drosophila.

Results

Herein we describe the distribution and evolution of Mar, a MITE family of hAT transposons, in Drosophilidae species. In silico searches and PCR screening showed that Mar distribution is restricted to the willistoni subgroup of the Drosophila species, and a phylogenetic analysis of Mar indicates that this element may have originated prior to the diversification of these species. Most of the Mar copies in D. willistoni present conserved target site duplications and TIRs, indicating recent mobilization of these sequences. We also identified relic copies of potentially full-length Mar transposon in D. tropicalis and D. willistoni. The phylogenetic relationship among transposases from the putative full-length Mar and other hAT superfamily elements revealed that Mar is placed into the recently determined Buster group of hAT transposons.

Conclusion

On the basis of the obtained data, we can suggest that the origin of these Mar MITEs occurred before the subgroup willistoni speciation, which started about 5.7 Mya. The Mar relic transposase existence indicates that these MITEs originated by internal deletions and suggests that the full-length transposon was recently functional in D. willistoni, promoting Mar MITEs mobilization.

Phylogenetic relationships and macro-evolutionary patterns within the Drosophila tripunctata "radiation" (Diptera: Drosophilidae)

Despite previous efforts, the evolutionary history of the immigrans-tripunctata clade remains obscure in part due to its hypothesized origin through a rapid radiation. We performed a supermatrix analysis (3,243 base pairs) coupled with richness patterns, environmental phylogenetic signal and radiation tests in order to address phylogenetic relationships and macro-evolutionary hypotheses within this complex group of species. We propose a well-supported evolutionary scenario for the immigrans-tripunctata clade species, in which the tripunctata "radiation" was monophyletic and subdivided into three main lineages: the first including D. pallidipennis (pallidipennis group) imbedded among members of the tripunctata group; the second clustering the cardini and guarani groups; and the third grouping representatives from the tripunctata, calloptera and guaramunu groups. Therefore, we hypothesize that the tripunctata group encompasses a diphyletic taxon, with one clade including the pallidipennis group and the other showing a close affinity to the calloptera and guaramunu groups. Our results also suggest that niche evolution seems to have played a central role in the evolutionary history of the tripunctata species "radiation" allowing effective dispersion and diversification in the Neotropics, possibly in a southwards direction. Although the data as a whole support the notion that this occurred through rapid and successive speciation events, the radiation hypothesis remains to be further corroborated.

Harrow: new Drosophila hAT transposons involved in horizontal transfer

In this study we characterize the transposable elements harrow, which belong to the hAT superfamily of DNA transposons. Searches for harrow sequences were performed in 65 Drosophilidae species, mainly representing Neotropical and cosmopolitan groups from the genus Drosophila. The nucleotide divergence among elements found in these species suggests that harrow sequences could be clustered in a subfamily. The patchy distribution throughout the genus Drosophila and the high similarity presented between all harrow sequences indicate that horizontal transfer could play a major role in the evolution of harrow elements. The results obtained suggest an evolutionary scenario in which harrow would have undergone multiple horizontal transfer events in the Neotropics, involving D. tripuncatata, D. mojavensis (Subgenus Drosophila) and several species of the willistoni and saltans groups (subgenus Sophophora).

Detection of P element transcripts in embryos of Drosophila melanogaster and D. willistoni

The P element is one of the most thoroughly studied transposable elements (TE). Its mobilization causes the hybrid dysgenesis that was first described in Drosophila melanogaster. While studies of the P element have mainly been done in D. melanogaster, it is believed that Drosophila willistoni was the original host species of this TE and that P was transposed to the D. melanogaster genome by horizontal transfer. Our study sought to compare the transcriptional behavior of the P element in embryos of D. melanogaster, which is a recent host, with embryos of two strains of D. willistoni, a species that has contained the P element for a longer time. In both species, potential transcripts of transposase, the enzyme responsible for the TE mobilization, were detected, as were transcripts of the 66-kDa repressor, truncated and antisense sequences, which can have the ability to prevent TEs mobilization. The truncated transcripts reveal the truncated P elements present in the genome strains and whose number seems to be related to the invasion time of the genome by the TE. No qualitative differences in antisense transcripts were observed among the strains, even in the D. willistoni strain with the highest frequency of heterochromatic P elements.

Evolution of Tom, 297, 17.6 and rover retrotransposons in Drosophilidae species

LTR retrotransposons are the most abundant transposable elements in Drosophila and are believed to have contributed significantly to genome evolution. Different reports have shown that many LTR retrotransposon families in Drosophila melanogaster emerged from recent evolutionary episodes of transpositional activity. To contribute to the knowledge of the evolutionary history of Drosophila LTR retrotransposons and the mechanisms that control their abundance, distribution and diversity, we conducted analyses of four related families of LTR retrotransposons, 297, 17.6, rover and Tom. Our results show that these elements seem to be restricted to species from the D. melanogaster group, except for 17.6, which is also present in D. virilis and D. mojavensis. Genetic divergences and phylogenetic analyses of a 1-kb fragment region of the pol gene illustrate that the evolutionary dynamics of Tom, 297, 17.6 and rover retrotransposons are similar in several aspects, such as low codon bias, the action of purifying selection and phylogenies that are incongruent with those of the host species. We found an extremely complex association among the retrotransposon sequences, indicating that different processes shaped the evolutionary history of these elements, and we detected a very high number of possible horizontal transfer events, corroborating the importance of lateral transmission in the evolution and maintenance of LTR retrotransposons.

The hobo transposon and hobo-related elements are expressed as developmental genes in Drosophila

Transposable elements comprise a significant part of genomes and are involved in their evolvability. The hobo element is found as an active class II transposable element in Drosophila melanogaster that is able to induce gonadal dysgenesis. Some hobo-related sequences (hRSs) are thought to be relics of old "hobo" invasions, and are therefore ancient genomic constituents. However, some of these hRSs are still mobile. The present study analyzed the expression pattern of hobo and a particular type of hRSs, hobo(VAHS). Both elements were shown to be expressed as sense and antisense mRNA transcripts. Expression analysis in whole mount embryos revealed a pattern similar to that of some developmental regulatory genes. Here we suggest that cis-regulatory sequences similar to those in developmental genes exist in hobo sequences. Therefore, hobo mobilization may contribute to the development of new regulatory networks during genomic evolution.

Phylogeny of the Drosophila mesophragmatica group (Diptera, Drosophilidae): an example of Andean evolution

The mesophragmatica group of Drosophila belongs to the virilis-repleta radiation of the Drosophila subgenus. This group comprises 13 Neotropical species that are endemic to the South-American continent and seem to be fundamentally Andean in their distribution. The mesophragmatica-group phylogeny has been inferred previously by other authors based on morphological, cytological, and isozyme analyses. However, the relationships within the group have not yet been completely resolved, although its monophyletic origin has already been confirmed by molecular data. This work attempts to enhance the molecular approach to the relationships among the species of the mesophragmatica group, using both nuclear and mitochondrial markers. Phylogenetic analyses were performed using fragments of the nuclear alcohol dehydrogenase (Adh; 631 bp), alpha-methyldopa (Amd; 1211 bp), dopa-decarboxylase (Ddc; 1105 bp), and hunchback (Hb; 687 bp) genes and the mitochondrial cytochrome oxidase subunit II (COII; 672 bp) gene, and included a total of 4306 bp. The sequences obtained for eight representatives of the mesophragmatica group were analyzed both individually and in combination by distance methods, maximum parsimony, and maximum likelihood. Our results support subdivision of the mesophragmatica group into three main lineages: the first is composed of D. viracochi; the second comprises a clade grouping the sibling species D. pavani and D. gaucha; and the third encompasses D. gasici, D. brncici, and D. mesophragmatica. The best supported scenario suggests that D. viracochi is an early offshoot in the mesophragmatica group, with this and other early branchings occuring in the Pliocene/Pleistocene Epochs, possibly associated with Andean glacial refuges. Also based on the phylogenies obtained, we present a genealogical view of the evolution of previously described characters within the group.

Analysis of phenotypes altered by temperature stress and hipermutability in Drosophila willistoni

Drosophila willistoni (Sturtevant, 1916) is a species of the willistoni group of Drosophila having wide distribution from the South of USA (Florida) and Mexico to the North of Argentina. It has been subject of many evolutionary studies within the group, due to its considerable ability to successfully occupy a wide range of environments and also because of its great genetic variability expressed by different markers. The D. willistoni 17A2 strain was collected in 1991 in the state of Rio Grande do Sul, Brazil (30°05'S, 51°39'W), and has been maintained since then at the Drosophila laboratory of UFRGS. Different to the other D. willistoni strains maintained in the laboratory, the 17A2 strain spontaneously produced mutant males white-like (white eyes) and sepia-like (brown eyes) in stocks held at 17°C. In order to discover if this strain is potentially hypermutable, we submitted it to temperature stress tests. Eighteen isofemale strains were used in our tests and, after the first generation, all the individuals produced in each strain were maintained at 29°C. Different phenotype alterations were observed in subsequent generations, similar to mutations already well characterized in D. melanogaster (white, sepia, blistered and curly). In addition, an uncommon phenotype alteration with an apparent fusion of the antennae was observed, but only in the isofemale line nº 31. This last alteration has not been previously described as a mutation in the D. melanogaster species. Our results indicate that the D. willistoni 17A2 strain is a candidate for hypermutability, which presents considerable cryptic genetic variability. Different factors may be operating for the formation of this effect, such as the mobilization of transposable elements, effect of inbreeding and alteration of the heat-shock proteins functions.

The hobo-related elements in the melanogaster species group

The hobo-related sequences (hRSs) were considered as degenerate and inactive elements until recently, when one mobilizable copy was described. Using this sequence as the initial seed to search for homologous sequences in 12 available Drosophila genomes, in addition to searching for these sequences by PCR and Southern blot in nine other species, we found homologous sequences in every species of the Drosophila melanogaster species subgroup. Some evidence suggests that these non-autonomous sequences were kept mobilizable for at least 0.4 million years. Also, some very short sequences with miniature inverted-repeat transposable element (MITE) characteristics were found among these hRSs. These hRSs and their 'MITE-like' counterparts could provide a good example of the steps proposed in models that describe the MITEs origin.

Multiple invasions of Errantivirus in the genus Drosophila

Aiming to contribute to the knowledge of the evolutionary history of Errantivirus, a phylogenetic analysis of the env gene sequences of Errantivirus gypsy, gtwin, gypsy2, gypsy3, gypsy4 and gypsy6 was carried out in 33 Drosophilidae species. Most sequences were obtained from in silico searches in the Drosophila genomes. The complex evolutionary pattern reported by other authors for the gypsy retroelement was also observed in the present study, including vertical transmission, ancestral polymorphism, stochastic loss and horizontal transfer. Moreover, the elements gypsy2, gypsy3, gypsy4 and gypsy6 were shown to have followed an evolutionary model that is similar to gypsy. Fifteen new possible cases of horizontal transfer were suggested. The infectious potential of these elements may help elucidate the evolutionary scenario described in the present study.

The LTR retrotransposon micropia in the cardini group of Drosophila (Diptera: Drosophilidae): a possible case of horizontal transfer

The presence of the micropia retroelement from the Ty1-copia family of LTR retroelements was investigated in three species of the Drosophila cardini group. Southern blot analysis suggested the existence of at least four micropia copies in the genomes of D. cardinoides, D. neocardini and D. polymorpha populations. The high sequence similarity between dhMiF2 and Dm11 clones (micropia retroelements isolated from D. hydei and D. melanogaster, respectively) with micropia sequences amplified from D. cardini group genome supports the hypothesis that this retroelement plays an active role in horizontal transfer events between D. hydei and the D. cardini group.