Association of telomeric regions of salivary gland chromosomes in Drosophila species of the virilis group]

The frequency of participating salivary gland chromosomes in telomeric associations and specific combinations of associated chromosomes were studied in the following species belonging to "virilis" group of Drosophila: D. virilis, D. texana, D. littoralis Sokolov and D. imeretensis Sokolov. In all species studied predominantly telomeres of two chromosomes form an association. In females of the species mentioned the X-chromosome takes part in association twice as frequent as in males. The total length of the chromosome and the presence of subterminal inversions may sometimes influence the frequency of participating the chromosome in associations. However, the data obtained enable to postulate that internal homology of telomeric regions plays the main role in the process. The equal frequency of participating in telomeric associations for definite chromosomes in species studied may resemble the phylogenetic relation of the species.     

QTL analysis of variation in male courtship song characters in Drosophila virilis

We have used a quantitative trait locus (QTL) mapping approach to study the genetic basis of differences between two Drosophila virilis strains representing extreme phenotypes in two song characters, the number of pulses in a pulse train (PN) and the length of a pulse train (PTL). Variation in these characters among 520 F2 males was studied by single-marker analysis and composite interval mapping (CIM) using a recombination linkage map constructed for 26 microsatellite markers. In single-marker analysis, two adjacent microsatellite markers on the third chromosome, msat19 and vir84 explained 13.8 and 12.4% of the variation in PN and 9.9 and 6.5% of the variation in PTL, respectively. CIM analysis revealed significant QTLs affecting PN, located on the X and the second, third and fourth chromosome of D. virilis, while variation in PTL was attributable to QTLs located only on the third chromosome.     

THE GENETIC BASIS OF EVOLUTION OF THE MALE COURTSHIP SOUNDS IN THE DROSOPHILA VIRILIS GROUP

When courting, males of the Drosophila virilis group vibrate their wings and emit species-specific courtship sounds consisting of trains of polycyclic sound pulses. To analyze the genetic basis of evolutionary changes in the sounds we made an F₁ diallel set of reciprocal crosses between the members of the virilis phylad of the group (two stocks of D. virilis and one of D. americana americana, D. a. texana, D. novamexicana, and D. lummei). We also crossed the D. virilis stocks with the members of the montana phylad of the same group (D. kanekoi, D. littoralis, D. borealis, D. flavomontana, D. lacicola, and D. montana) and made a backcross (D. virilis x D. littoralis) x D. virilis using a D. virilis marker stock (b; sv t tb gp; cd; pe). The sounds of the hybrids were analyzed using the following parameters: the length of a pulse train (PTL), the number of pulses in a train (PN), the interpulse interval (IPI), the length of a pulse (PL), the number of cycles in a pulse (CN), and the length of a cycle (CL). In the virilis phylad, the differences between species appeared to be determined mainly by autosomal genes in each sound trait. The heritabilities (narrow-/broad-sense) obtained from the diallel tables were the following: PTL 0.662/0.817, PN 0.651/0.841, IPI 0.193/0.546, PL 0.408/0.552, CN 0.425/0.719, and CL 0.361/0.764. The direction of dominance is for longer PTL, higher PN and CN, and shorter IPI and CL. PL shows ambidirectional dominance. In the sounds of the virilis phylad species, PTL and PL seem to be phenotypically the most important parameters, since their components (PN and IPI for PTL, CN and CL for PL) are negatively correlated. In crosses between D. virilis and D. littoralis or D. flavomontana reciprocal hybrids differed from each other in PTL, IPI, PL, and CN indicating X-chromosomal or cytoplasmic inheritance. In the backcrosses between D. virilis and D. littoralis the role of the X chromosome was ascertained to be decisive. We conclude that an X-chromosomal major change allowing variation in IPI has occurred during the separation of the two D. virilis group phylads, the long IPI allowing variation also in PL (and CN). The evolution of the sounds in the virilis phylad has probably gone towards longer and denser pulse trains, while in the montana phylad the sounds have evolved in different directions.     

Nucleotide variation at the no-on-transient A gene in Drosophila littoralis

The no-on-transient A (nonA) gene encodes a putative RNA-binding protein, and mutations in this gene are known to affect vision, male courtship song and viability in Drosophila melanogaster. Here we have sequenced the coding region of the nonA gene of Drosophila littoralis and compared it with those of Drosophila virilis and D. melanogaster. All portions of nonA appeared to be conserved between D. littoralis and D. virilis, while the 5' region of the gene of these two species showed high divergence from that of a more distantly-related species, D. melanogaster. The same was true for the glycine repeat regions. No significant deviation from neutrality was observed in the analysis of intraspecific nucleotide variation in 5' or 3' region of the nonA gene in D. littoralis population. Also, comparison of D. littoralis sequences with homologous sequence of D. virilis suggests that the gene is evolving neutrally in D. virilis group. Divergence of the 5' regions between D. virilis group species and D. melanogaster could be a result of positive selection, but this finding is obscured by the long divergence time of the species groups.     

Genetic analysis of female mating recognition between Drosophila ananassae and Drosophila pallidosa: application of interspecific mosaic genome lines

Drosophila ananassae and Drosophila pallidosa are closely related species that can produce viable and fertile hybrids of both sexes, although strong sexual isolation exists between the two species. Females are thought to discriminate conspecific from heterospecific males based on their courtship songs. The genetic basis of female discrimination behavior was analyzed using isogenic females from interspecific mosaic genome lines that carry homozygous recombinant chromosomes. Multiple regression analysis indicated a highly significant effect of the left arm of chromosome 2 (2L) on the willingness of females to mate with D. ananassae males. Not only 2L but also the left arm of chromosome X (XL) and the right arm of chromosome 3 (3R) had significant effects on the females' willingness to mate with D. pallidosa males. All regions with strong effects on mate choice have chromosome arrangements characterized by species-specific inversions. Heterospecific combinations of 2L and 3R have previously been suggested to cause postzygotic reproductive isolation. Thus, genes involved in premating as well as postmating isolation are located in or near chromosomal inversions. This conclusion is consistent with the recently proposed hypothesis that "speciation genes" accumulate at a higher rate in non-recombining genome regions when species divergence occurs in the presence of gene flow.     

Courtship Behavior Analysis in Three Sibling Species of the Drosophila virilis Group

Entomological Review - Courtship behavior was studied in three sibling species of the Drosophila virilis group: D. virilis, D. lummei, and D. littoralis. The latter species was represented by two...     

Variation and consistency of female preferences for simulated courtship songs in Drosophila virilis

To study the variation and consistency of song preferences in Drosophila virilis females, we played them species-specific song and songs with modified sound pulses and/or interpulse intervals on 3 consecutive days. Species-specific song was played again on the fourth day. All playbacks were done without the presence of males. About 62% of the females indicated their readiness to mate by spreading their wings in at least one of the trials. The proportion of the females responding to species-specific song was about twice that of the females responding to modified songs. The majority of females responded to only one song type, which suggests that the females varied in their preferences and that their preference windows were rather narrow. The females were consistent in their responsiveness to species-specific song played on 2 days. If the female responded to normal song during the first trial, the probability of her responding to the same song during the second trial increased by about 32%. The number of songs required by the females before responding in the two subsequent trials was also correlated within the females (repeatability 0.328). Repeatability of female preferences for male sexual traits is expected both in the viability and Fisherian models of sexual selection. Copyright 1999 The Association for the Study of Animal Behaviour.     

The nonA gene in Drosophila conveys species-specific behavioral characteristics

The molecular basis of species-specific differences in courtship behavior, a critical factor in preserving species boundaries, is poorly understood. Genetic analysis of all but the most closely related species is usually impossible, given the inviability of hybrids. We have therefore applied interspecific transformation of a single candidate behavioral locus, no-on-transient A (nonA), between Drosophila virilis and D. melanogaster, to investigate whether nonA, like the period gene, might encode species-specific behavioral information. Mutations in nonA can disrupt both visual behavior and the courtship song in D. melanogaster. The lovesong of nonA(diss) mutant males superficially resembles that of D. virilis, a species that diverged from D. melanogaster 40-60 mya. Transformation of the cloned D. virilis nonA gene into D. melanogaster hosts carrying a synthetic deletion of the nonA locus restored normal visual function (the phenotype most sensitive to nonA mutation). However, the courtship song of transformant males showed several features characteristic of the corresponding D. virilis signal, indicating that nonA can act as a reservoir for species-specific information. This candidate gene approach, together with interspecific transformation, can therefore provide a direct avenue to explore potential speciation genes in genetically and molecularly tractable organisms such as Drosophila.     

Variation in male wing song characters inDrosophila plantibia (Hawaiian picture-wingedDrosophila group)

The males of most species of the HawaiianDrosophila planitibia group produce songs when vibrating their wings during courtship. In four of the most recently evolved species,D. differens, D. planitibia, D. heteroneura, andD. silvestris, these songs are simple in structure and possess a higher and more variable carrier frequency than the songs of the more ancestral species of the group. In the present paper, we studied the variation in wing song production and song characters in aD. planitibia population. Some males vibrated their wings at a very low amplitude or slow speed, producing no detectable sound. Other males produced sound bursts varying in carrier frequency and burst length. The carrier frequency of the song depended mainly on the wing posture of the male during wing vibrations and was consistent for individual males. Variation between males of different isofemale progenies was not significant in any measured song trait. Songs of the males recorded in the present study differed, however, from songs of the males of a laboratory strain recorded earlier.     

Nucleotide and repeat length variation at the nonA gene of the Drosophila virilis group species and its effects on male courtship song

Genes found to affect male courtship song characters in Drosophila melanogaster are good candidates when tracing genes responsible for species-specific songs in other Drosophila species. It has previously been shown that Thr–Gly repeat length variation at the period gene affects song traits in D. melanogaster, which gives the repetitive regions a special interest. In this work, we have characterised the patterns of nucleotide variation for gene regions containing two Gly and one Gln–Ala repeat in another D. melanogaster song gene, no-on-transient A, in D. virilis group species. The levels of nucleotide variability in D. virilis nonA were similar to those found for other genes of the species, and the gene sequences showed no signs of deviation from neutrality. The Gly 2 repeat preceding the central domain of the gene exhibited length variation, which did not, however, correlate with song variation either within D. virilis or between the species of D. virilis group. The Gly 3 repeat located on the other side of the central domain showed amino acid divergence parallel to the consensus phylogeny of the D. virilis group species. The species of the virilis subgroup having Asn after the first three glycines in this repeat have simple songs with no species-specificity, while the species of the montana subgroup having two Gly or Asn–Ser in this site have unique courtship songs. Amino acid differences between the species in this repeat may, however, reflect species phylogeny rather than have an effect on song divergence per se.     

A framework physical map of Drosophila virilis based on P1 clones: applications in genome evolution

The analysis of patterns of genome evolution may help to evaluate the evolutionary forces that shape the composition and organization of the genome. Comparisons between the physical maps of divergent species can be used to identify conserved blocks of closely linked genes whose synteny is possibly under selective constraint. We have used in situ hybridization to determine the genomic position of 732 randomly selected clones from a bacteriophage P1 library of Drosophila virilis. The resulting map includes at least one clone in each of 69% of the subdivisions into which the D. virilis polytene chromosomes are divided. A subset of these clones was used to carry out a comparative physical analysis of chromosome 2 from D. virilis and from Drosophila montana. A number of discrepancies with the classical scenario of chromosome evolution were noted. The D. virilis P1 clones were also used to determine the physical relations between ten genes that are located in the X chromosome of Drosophila melanogaster between the markers crn (2F1) and omb (4C5-6). In this region, which is approximately 2 Mb in length, there have been at least six breakpoints since the divergence of the species, and six of the genes are found at widely scattered locations in the D. virilis X chromosome. However, a block of four functionally unrelated genes, including white, roughest, Notch, and dunce, seems to be conserved between the two species. Received: 1 March 1996 / Accepted: 8 February 1997     

The Genetic Basis of a Species-Specific Character in the Drosophila Virilis Species Group

The genetic basis of the species-specific dorsal abdominal stripe of Drosophila novamexicana was examined. The dorsal stripe is present in D. novamexicana and absent in all other members of the Drosophila virilis species group. Interspecific crosses between D. novamexicana and genetically marked D. virilis revealed that all four of the autosomes (except the tiny dot chromosome, which was not marked) and the sex chromosomes (the X and Y chromosome effects could not be disentangled) showed a significant effect on the width of the dorsal stripe. All the autosomes act approximately additively; only minor interactions were detected among them. No significant maternal effects were found. This means that a minimum of five loci are involved in the character difference between the two species, and this is the maximum number that this technique could discern. These results suggest that, based on the number of factors involved in the character difference, the inheritance of this character should be considered polygenic, but because chromosome 2 (the largest chromosome in the species) contributed over half of the variance toward the character difference, it is best to consider the inheritance oligogenic based on effect. The implications of these findings are discussed in light of the importance of macromutation in speciation and the sex chromosome theory of speciation.     

Resolving the phylogenetic relationships and evolutionary history of the Drosophila virilis group using multilocus data

The Drosophila virilis group is one of the major lineages of Drosophila previously recognised and it has been used as a model for different types of studies. It comprises 13 species whose phylogenetic relationships are not well resolved. In the present study, six nuclear genes (Adh, fused, Gpdh, NonA, CG9631 and CG7219) and the mitochondrial ribosomal RNA genes (12S-16S) have been used to estimate the evolutionary tree of the group using different methods of phylogenetic reconstruction. Different competing evolutionary hypotheses have also been compared using the Approximately Unbiased test to further evaluate the robustness of the inferred trees. Results are, in general, consistent with previous studies in recovering the four major lineages of the group (D. virilis phylad, Drosophila montana subphylad, Drosophila kanekoi subphylad and Drosophila littoralis subphylad), although D. kanekoi, D. littoralis and Drosophila ezoana are here inferred to be more closely related to the D. virilis phylad than to the D. montana subphylad. The age of the crown group, estimated with a Bayesian method that assumes a relaxed molecular clock, is placed in the late Miocene (～ 10 Mya). The oldest lineages also appeared during this period (～ 7.5 to ～ 8.9 Mya), while the ages of the basal nodes of the montana subphylad and the virilis phylad are located in the early Pliocene (～ 4.9 and ～ 4.1 Mya). Major cladogenesis events correlate to geological and palaeoclimatic occurrences that most likely affected the freshwater and deciduous forests where these species are found. The inferred biogeographical history of the group, based on the statistical dispersal-vicariance analysis, indicates that the last common ancestor of the group had a Holarctic distribution from which the North American and the Eurasian lineages evolved as a result of a vicariant event.     

Discordant Rates of Chromosome Evolution in the Drosophila Virilis Species Group

In Drosophila, the availability of polytene chromosome maps and of sets of probes covering most regions of the chromosomes allows a direct comparison of the organization of the genome in different species. In this work, we report the localization, in Drosophila virilis, D. montana, and D. novamexicana, of >100 bacteriophage P1 clones containing ~65 kilobase inserts of genomic DNA from D. virilis. Each clone hybridizes with a single euchromatic site in either chromosome 1 or chromosome 3 in D. virilis. From these data, it is possible to estimate the minimum number of inversions required to transform the map positions of the probes in one species into the map positions of the same probes in a related species. The data indicate that, in the D. virilis species group, the X chromosome has up to four times the number of inversions as are observed in chromosome 3. The first photographic polytene chromosome maps for D. montana and D. novamexicana are also presented.     

Copulatory courtship behavior and sine song as a mate recognition cue in Drosophila lini and its sibling species

Most Drosophila species sing species-specific pulse songs during their "precopulatory courtship." Three sibling species of the Drosophila montium species subgroup performed "copulatory courtship": males generated courtship songs by vibrating either wing only after mounting and during copulation. In these three species, strong sexual isolation was detected between D. ohnishii and D. lini and between D. ohnishii and D. ogumai, but not between D. lini and D. ogumai. Female showed strong repelling behavior when they were mounted by a heterospecific male in the species combinations including D. ohnishii, resulting in failure of the copulation attempt of the male. Acoustic analyses of courtship songs revealed that the pulse song was irregular, without any species-specific parameters, but that the frequency of the sine song was different among the three species in accordance with the modes of sexual isolation between them; it was significantly lower in D. ohnishii (mean ± SE = 193.0 ± 1.7 Hz) but higher in D. lini (253.4 ± 2.7 Hz) and D. ogumai (246.7 ± 5.3 Hz). We suggest that this difference in the sine song frequency is a sexual signal in the Specific Mate Recognition System (SMRS) among these three Drosophila species.     

A RAPD fingerprinting of sibling species of the Drosophila virilis group

A comparative analysis of the sibling species of Drosophila virilis was performed by RAPD-PCR technique using a set of random primers. The degree of relatedness was studied by cluster analysis (UPGMA) and multi-dimensional scaling. The resulting pattern of species relationships contradicts the classical taxonomy. The main result of the cluster analysis is that D. virilis does not cluster with the remaining three species of its phylad, while according to multidimensional scaling, D. virilis is equidistant from all the species of its group, from both the species of its phylad and the species of the montana phylad. The montana phylad is extremely heterogeneous; moreover, the species D. littoralis, D. ezoana, and D. kanekoi appear to be closer to the virilis phylad than to the other species of the montana phylad, wherein these species are traditionally included. The phylogenetic relationships between the studied species discovered using RAPD fingerprinting comply with the results obtained using protein markers and quantitative traits.     

The temperature sensitivity of mutations in species of the virilis group of Drosophila. II. The effect of temperature on the maternal effect on the puffed marker following hybridization

The influence of temperature (17 and 31 degrees) on the maternal effect of mutation Puffed (Pu) in Drosophila hybrids has been studied. In the hybrids female D. littoralis +/+ x male D. virilis Pu/Pu, the stage of formation of black ring on anterior spiracles in the 3rd larval instar is sensitive to 31 degrees. In the hybrids female D. virilis Pu/Pu x male D. littoralis +/+, the expression of Pu gene manifests the maternal effect and as a result, two temperature-sensitive stages are found. The first one--onset of embryogenesis (2 to 4 hrs). At the temperature 17 degrees, the penetrance of Pu increases. The second stage is sensitive to 31 degrees and coincides with the period of black rings formation on anterior spiracles in the 3rd laval instar. It has been shown that at least two genetic systems take part in the formation of this feature. One group of genes controls the maternal effect and is sensitive to low temperature in the early embryogenesis of the hybrids female D. virilis x male D. littoralis. The second one--Pu gene and its modifiers--is active during the 2nd half of the 3rd larval instar and is heat-sensitive.     

黑蚱蝉鸣声的结构和音色特征

本文对北京、河北和福建等地黑蚱蝉(Cryptotympana atrata Fabricius)的三种鸣声进行了分析,并对发声机理进行了讨论。 黑蚱蝉野外的自然鸣声具有基本相同的结构层次,都由重复频率为43—49Hz的节奏组成,每个节奏含有4个单音节,每个单音节含有3个脉冲群,每个脉冲群含有若干个脉冲。但是音色有明显的差异,即分别为单音色、双音色和具有高幅低频声的复合声。黑蚱蝉室内的惊鸣声和自鸣声,虽然音色有一定的变化,但仍保持自然鸣声的结构层次。鸣声的结构层次明显取决于发声膜的结构特征,这表明具有种类的特性。音色的差异性不仅与调音、扩音结构的功能有关,而且可能与发声膜的力学性质和发声的原初过程有关,即可能具有地区性和种下差异。 这些结果可为蝉类发声机制和有害昆虫声引诱的声学模型的研究提供依据。     

Localization of ecs, dor and swl genes in eight Drosophila species]

The DNA sequences from Drosophila melanogaster early ecdysterone-inducible puff 2B have been located in 8 Drosophila species by in situ hybridization. The location site of the ecs, dor and swi genes in D. funebris, D. virilis, D. hydei, D. repleta, D. mercatorum, D. paranaensis is a puff on the telomeric and of X chromosome; in D. kanekoi it is the puff in distal part of X chromosome; and in D. pseudoobscura it is the puff in proximal portion of X chromosome. So, conservative organization of DNA sequences located in D. melanogaster 2B puff could be suggested. Dispersed distribution of some DNA segments from the region studied in D. hydei chromosomes was revealed.