Melanogaster Species Group Research Articles

Chromosomal polymorphism in Indian populations of Drosophila bipectinata Duda

Drosophila bipectinata, a member of the melanogaster species group, is a common and wide-spread species in the Indian subcontinent. A geographic survey of inversion polymorphism has been carried out in Indian populations. Altogether, nine paracentric inversions are detected in the populations examined during this study. Of the nine inversions, two have been described earlier by Bock from laboratory populations established from Borneo, Thailand and the Philippines. The possible relationship between inversions and different environmental conditions is discussed.

ADAPTATIONS TO TEMPERATE CLIMATES AND EVOLUTION OF OVERWINTERING STRATEGIES IN THE DROSOPHILA MELANOGASTER SPECIES GROUP.

The Drosophila melanogaster species group is considered to have originated in the tropics and only recently invaded temperate habitats. The temperate species of this group that were studied here may be subdivided into the warm-temperate species (D. lutescens and D. rufa) and the cool-temperate species (species of the auraria complex). The warm-temperate species were more cold-hardy than were their tropical relatives (D. takahashii or D. melanogaster) at the larval and imaginal stages, and the cool-temperate species were more cold-hardy than the warm-temperate species, although only at the imaginal stage. However, these species showed little or no intraspecific variation in cold-hardiness, in spite of great variation in winter temperature within the species' ranges. It is assumed that cold-hardiness is one of the main factors restricting their distributions at high latitudes and that it is the key for evolution of the warm- and cool-temperate species from their subtropical or warm-temperate ancestors. Both warm- and cool-temperate species had photoperiodically controlled reproductive diapause. In the cool-temperate species, the development of cold-hardiness was affected by diapause, but diapause had little or no effect on cold-hardiness in the warm-temperate species. Critical daylengths and the diapause rates varied from species to species according to variation in their overwintering plans and also varied geographically in consequence of their adaptation to local climates. Species showed different responses to temperature in preimaginal and ovarian development. These differences are considered to reflect adaptation to different environmental temperatures.

Nucleotide sequence of the Adh gene region of Drosophila pseudoobscura: evolutionary change and evidence for an ancient gene duplication.

The alcohol dehydrogenase (Adh) locus (ADH; alcohol: NAD+ oxidoreductase, EC 1.1.1.1) of Drosophila pseudoobscura was cloned and sequenced. Forty-five percent of the "effectively silent sites" have changed between Adh in D. pseudoobscura of the obscura species group and the homologous DNA sequence in D. mauritiana, the latter representing the melanogaster species group. The untranslated leader sequence of the adult transcript of D. pseudoobscura has two deletions relative to the D. mauritiana message. The ADH protein sequences of D. pseudoobscura is missing the third and fourth amino acids at the N-terminus relative to the D. mauritiana enzyme. Of the remaining 254 amino acid positions, 27 (10.64%) differ between the two species. Amino acid replacements are randomly distributed into hydrophilic and hydrophobic domains of ADH. However, replacement substitutions are distributed nonrandomly across the three exons among D. pseudoobscura and members of the melanogaster subgroup, suggesting that functional constraints across the exons are different. Surprisingly, silent substitutions are also nonrandomly distributed with the third exon being the most divergent. This pattern suggests possible selective constraints on supposedly neutral silent substitutions and/or variation in underlying mutation rates across the gene. The presence of transcriptional and translational signals at the beginning and end of conserved sequences 3' to Adh implies the existence of a previously undescribed gene. Codon usage and patterns of nucleotide divergence are consistent with a protein coding function for this gene. In addition, conservation of nucleotide and amino acid sequence and similarity in hydropathy plots suggests that the gene 3' to Adh represents an ancient duplication of the Adh gene.

Chromosome inversion polymorphism in natural populations of Drosophila punjabiensis Parshad and Paika

Drosophila punjabiensis, a member of the montium subgroup of the melanogaster species group is a very common and widespread species of Drosophila in the Indian subcontinent. Analysis of different geographic populations of this species in India has revealed altogether nine paracentric inversions. The relationship between inversions and the different environmental conditions is discussed. The pattern of inversion polymorphism in D. punjabiensis and its sibling species, D. jambulina are compared.

Distribution and conservation of mobile elements in the genus Drosophila.

Essentially nothing is known of the origin, mode of transmission, and evolution of mobile elements within the genus Drosophila. To better understand the evolutionary history of these mobile elements, we examined the distribution and conservation of homologues to the P, I, gypsy, copia, and F elements in 34 Drosophila species from three subgenera. Probes specific for each element were prepared from D. melanogaster and hybridized to genomic DNA. Filters were washed under conditions of increasing stringency to estimate the similarity between D. melanogaster sequences and their homologues in other species. The I element homologues show the most limited distribution of all elements tested, being restricted to the melanogaster species group. The P elements are found in many members of the subgenus Sophophora but, with the notable exception of D. nasuta, are not found in the other two subgenera. Copia-, gypsy-, and F-element homologues are widespread in the genus, but their similarity to the D. melanogaster probe differs markedly between species. The distribution of copia and P elements and the conservation of the gypsy and P elements is inconsistent with a model that postulates a single ancient origin for each type of element followed by mating-dependent transmission. The data can be explained by horizontal transmission of mobile elements between reproductively isolated species.

MATING BEHAVIOR AND THE EVOLUTION OF DROSOPHILA MAURITIANA.

Drosophila mauritiana is closely related to D. melanogaster and D. simulans, from which it differs obviously morphologically in having narrow posterior lobes of the male genital arches (Tsacas and David, 1974). Studies of allozyme frequencies (Gonzailez et al., 1982), some DNA components (see Dover, 1982), polytene chromosome banding sequences (Lemeunier and Ashburner, 1976), and hybrid fertility (David et al., 1974) indicate that it is most closely related to simulans. Drosophila mauritiana is endemic to the island of Mauritius, from which simulans and melanogaster are absent. They are however present on the neighboring island of Reunion from which mauritiana is absent (David and Tsacas, 1975). Mauritius and Reunion are approximately 320 km apart, and 960 km and 720 km from Madagascar, respectively. The only other melanogaster group species on Mauritius are D. ananassae and D. parabipectinata (David and Tsacas, 1975). Their courtships differ considerably from those of the melanogaster subgroup (Narda, 1968; Hegde and Krishnamurthy, 1979). In addition to interest in how its courtship has changed from that of its muchstudied sibling species, mauritiana may provide a test of two evolutionary questions. The first is whether changes in mating behavior, narrow variability of courtship signals, and specificity of mating responses can evolve and be maintained in complete allopatry, i.e., in a solely intraspecific context. This is therefore partly a test of Mayr's (1970 p. 67) prediction

DOES ASYMMETRICAL MATING PREFERENCE SHOW THE DIRECTION OF EVOLUTION?

The analysis of present behavior patterns is often a useful tool in our attempts to decipher the past. Studies of reproductive behavior have proven particularly fruitful in this regard, for the extent and type(s) of ethological barriers between two or more species can sometimes offer clues concerning key events in their evolutionary history. The usual approach is to obtain data on the relative willingness of individuals to mate, indicated by some type of isolation index. This index may actually be a function of both sex drive and discrimination. The strength of the isolation present-as measured by the isolation index-together with other relevant information, is then used to determine evolutionary patterns. Such investigations have shown that certain species pairs exhibit asymmetrical isolation. Asymmetrical isolation is said to exist when sexual isolation between the females of one population (population A) and the males of another population (population B) is greater than that found in the reciprocal crosses (females of population B with males of population A). One might expect that the rate of the development of sexual isolation between two populations would, by chance, occasionally be asymmetrical. Indeed, where isolation is not complete, equality of isolation between populations may be the exception rather than the rule. On the other hand, since the development of reproductive isolation is crucial to the speciation process, the presence of asymmetrical mating preferences may actually reflect the mechanism by which speciation has occurred. Toward this end, Kaneshiro (1976) and Watanabe and Kawanishi (1979) proposed models whereby they suggested that the direction of evolution can be determined by the examination of patterns of asymmetrical isolation. Kaneshiro (1976) and later Ohta (1978) uncovered asymmetry in mating preferences among several Hawaiian Drosophila species. Kaneshiro's model, upon which Ohta elaborated, suggested that the females of the putative ancestral species are more isolated from males of the putative derived species than are the derived females from the ancestral males. In 1979 Watanabe and Kawanishi offered a contrasting model based on their experimental work with the Drosophila melanogaster species group (Watanabe and Kawanishi, 1979). Here they had found an asymmetrical mating preference whereby the females of the putative derived species were more isolated from the males of the putative ancestral species than were the ancestral females from the derived males. This seemed also to be true of the published work on the virilis group. Thus, for any given set of asymmetrical isolation indices, the direction of evolution proposed by Watanabe and Kawanishi is exactly opposite to that suggested by Kaneshiro. If either of these two models is generally correct, a very powerful tool is available to researchers. Both are adequate to explain the data for which they were designed. A good test of these models would be to apply them to new data. For this purpose we will use the results of a study made on the Drosophila arizonensis-Drosophila majavensis species pair in which we investigated the reproductive relationships between various allopatric and sympatric populations of the two species (Wasserman and Koepfer, 1977). We found a much higher level of sexual isolation between sympatric populations

MALE MATING DISCRIMINATION IN DROSOPHILA MELANOGASTER, D. SIMULANS AND THEIR HYBRIDS.

Little is known about the relative importance of the sexes in maintaining reproductive isolation between closely related species in Drosophila. A great deal of evidence demonstrating the importance of females in sexual selection in Drosophila has been amassed, but this work concerns only intraspecific courtship and copulation (Petit and Ehrman, 1969; Spiess, 1970; Ehrman, 1972). The picture regarding interspecific courtship is not clear. It may be that the female determines whether or not copulation will occur between closely related species to the same extent as she does within her own species (Merrell, 1954). However, it may be that males can discriminate well, and do not court interspecifically as readily or persistently as they do intraspecifically. If this is the case, males would exert primary control over the maintenance of ethological isolating barriers, regardless of the female's discriminatory abilities, since the initiates courtship and copulation. Spieth (1974) has argued that in Drosophila it is indeed the that is primarily responsible for sexual isolation in nature. One of the best ways to determine whether or not a has an important role in maintaining ethological isolating barriers is actually to observe and measure interspecific courtship. Direct observation experiments using the Drosophila melanogaster group of species has added support to Spieth's position. Von Schilcher and Dow (1977) found that Drosophila melanogaster and Drosophila simulans do not court females of their sibling species as persistently or intensely as their own and that it is the males who most often terminate interspecific courtship, while it is the females who usually cause the termination of intrasDecific courtshiD. Manning (1959), working with D. melanogaster and D. simulans, also found a reluctance on the part of males to court interspecifically, but in addition, he found that this reluctance was stronger in D. simulans. Von Schilcher and Dow (1977) did not find such a difference between the species. Both Manning (1959) and von Schilcher and Dow (1977) looked only at pair matings. To date, one has reported if males in the D. melanogaster species group discriminate to the same extent when both conspecific females and females from a closely related species are present, a situation that is presumably the more natural and meaningful one. Also, mating discrimination in the hybrids of D. melanogaster and D. simulans has not been studied extensively. Von Schilcher and Manning (1975) measured mating speed and certain parameters of the wing vibration of hybrids, but they did not analyze their discriminatory abilities. Possibly an analysis of the discrimination shown by hybrids will give some clue to the genetic basis of discrimination in the parent species. The purpose of this study, then, was to examine the abilities of D. melanogaster, D. simulans and their hybrids to discriminate between conspecific and nonconspecific females in no choice pair matings and male choice situations to evaluate both the probable importance of the sex in maintaining ethological isolating barriers and the genetic basis of these abilities.

Pattern of chromosomal polymorphism in Drosophila jambulina Parshad and paika.

Drosophila jambulina is a new species belonging to the montium subgroup of the melanogaster species group of the subgenus Sophophora. It is one of the commonest and most widespread species in India. A map of its salivary gland chromosomes has been constructed and some identifiable landmarks in each arm of the chromosome are recognized. Analysis of population samples from eight different geographical localities has yielded five different autosomal inversions, all confined to the right arm of 3rd chromosome only. However, irradiation study has shown that the distribution of induced rearrangements is more or less at random throughout the chromosomes in this species.

GENETIC DIFFERENTIATION WITHIN THE MELANOGASTER SPECIES GROUP OF THE GENUS DROSOPHILA (SOPHOPHORA).

The melanogaster subgroup is one of twelve in the Drosophila melanogaster species group (Bock and Wheeler, 1972). For many years this subgroup only comprised the sibling species D. melanogaster and D. simulans. More recently four new African species, belonging to the melanogaster subgroup, have been described: D. yakuba (Burla, 1954); D. teissieri (Tsacas, 1971); D. mauritiana (Tsacas and David, 1974); and D. erecta (Tsacas and Lachaise, 1974). These six species can be considered siblings as the females are nearly indistinguishable and male identification depends on differences in the genitalia. Especially melanogaster, simulans and mauritiana appear to be closely related as reproductive isolation is not complete between these species, at least under laboratory conditions (David et al., 1974). In the present paper the genetic relationships between the six sibling species of the melanogaster subgroup are analyzed, in order to obtain information about the degree of genetic diversity hidden under the great phenotypic resemblance. In this study relationships between the six species are investigated by means of electrophoresis of enzymes. The observed differences in migration distances between species can be expressed in terms of genetic distance (Nei, 1972). Lemeunier and Ashburner (1976) investigated the evolutionary relationships between the same six species by an analysis of the banding patterns of their polytene chromosomes. This enables a comparison of the results obtained by both, quite different methods.

Isozyme variation and phylogenetic relationships among six species of the montium subgroup of the Drosophila melanogaster species group

Isozyme variation and phylogenetic relationships among six species of the montium subgroup of the Drosophila melanogaster species group

Drosohila Agumdensis, sp. nov. from Karnataka, South India (Diptera : Drosophilidae)

Drosophila agumbensts, sp. nov., a member of the monttum subgroup of the melanogaster species group collected from Agumbe (a part of Western Ghats) is described. The systematic position and the affinities of this new species are discussed.

Two New Species ofDrosophila (MelanogasterSpecies Group) (Diptera : Drosophilidae)

AbstractTwo species, D. giriensis and D. gundensis, members of takahashii and montium subgroups respectively, belonging to melanogaster species group collected from Western Ghats, are described. Their taxonomic status and relationships are discussed.

ON THE ETHOLOGICAL DIFFERENTIATION OF DROSOPHILA ANANASSAE AND DROSOPHILA PALLIDOSA IN SAMOA.

A number of significant studies of genetic divergence and speciation in island populations of Drosophila have been undertaken in recent years. Certainly the grandest example of this has been the detailed study of the spectacular array of Drosophila species native to the Hawaiian Islands begun under the leadership of the late Professor Wilson S. Stone of the University of Texas and Professor D. Elmo Hardy of the University of Hawaii, and still being carried on by Hardy and a number of their colleagues; e.g., see Carson et al. (1970). Other island groups and Drosophila species have also been investigated by Stone and others at the University of Texas. Among these studies are those on Drosophila ananassae populations from island groups in the central and western Pacific Ocean, including light (brownish-yellow) and dark (blackish-brown) D. ananassae-like populations found on the American Samoan island of Tutuila. These populations are especially interesting in that, aside from the pigmentation difference, they are morphologically nearly indistinguishable and, in spite of exhibiting no apparent postmating reproductive barriers (Stone et al., 1966), they coexist together on this island as separate, reproductively isolated units. That they are sexually isolated has been shown cytologically (Futch, 1966) and ethologically (Futch, 1966; Spieth, 1966) with strains from Pago Pago, Tutuila. In recent years other collections of similar light and dark D. ananassae-like flies have been obtained from other islands in the Samoan archipelago as well as from islands in the Fijian group. Based mainly on the cytological and ethological evidence cited above concerning the genetic isolation of these light and dark forms, Bock and Wheeler (1972) recognize the two as distinct species belonging to the D. ananassae subgroup of the D. melanogaster species group of Drosophila. The dark flies have been identified as Drosophila ananassae Doleschall, a polytypic, widespread (circumtropical) domestic species of the tropical and sub-tropical world, whereas they describe the light flies as Drosophila pallidosa. This recently described species has a relatively localized distribution presently known only to include the southcentral Pacific islands of Samoa and Fiji where it exists side-by-side with its widely distributed sibling, D. ananassae. That two such very closely related, potentially interfertile sympatric species have been found living together successfully and separately in the island groups of Samoa and Fiji seems to warrant further investigation. As a part of this continuing investigation, populations from other islands of the Samoan group have been analyzed cytologically and for crossing fertility as stocks have become available to me.

SELECTIVE MATING AND EYE PIGMENTATION: AN ANALYSIS OF THE VISUAL COMPONENT IN THE COURTSHIP BEHAVIOR OF DROSOPHILA MELANOGASTER.

A number of investigations have shown that in competitive mating tests mutant Drosopkila are at a disadvantage when competing with wild type flies. Over long time intervals the mutant genes are either eliminated or maintained at a very low frequency in the population (Reed and Reed, 1948; Merrell and Underhill, 1956). This disadvantage has usually been attributed to a reduction in fitness on the part of the mutant when competing for the available food supply. Behavior is also a component of fitness, and there is evidence indicating that the disadvantage exhibited by many mutant genotypes is due to some impairment of their mating behavior. Reed and Reed (1950) found that males from the sex linked white eye mutation (w) of Drosophila melanogaster were at a considerable disadvantage when in competition with wild type males. Bastock (1956) demonstrated that the yellow mutant (y) of D. melanogaster gives rise to males which show a quantitative change in the wing vibration element of the courtship display. The slight reduction in mean vibration bout lengths of the mutants results in their being at a disadvantage. Petit (1959) found that wild type males had an advantage over wkite eye and Bar eyed males in a competitive situation, this she attributed to differences in the wing vibration component of the courtship display. Geer and Green (1962) were unable to confirm this effect on wing vibration in studies with vestigial mutant males. Geer and Green (loc. cit.) working with a series of eye pigment mutants obtained evidence of a relationship between the amount of eye pigmentation and mating success; the greater the pigment density the greater the mating success. This is a particularly interesting finding since it has been argued that vision plays only a minor role in the courtship of Drosophila melanogaster (Spieth and Hsu, 1950), although it has an important influence on the courtship of certain other members of the melanogaster species group (Grossfield, 1968). Geer and Green (loc. cit.) showed that the disadvantage suffered by the eye pigment mutants was no longer present when matings were allowed to take place in total darkness, indicating that vision may also be important in the courtship of Drosophila melanogaster. In none of the investigations where eye mutants have been used, has the behavior of the animals been observed, mating success being measured by progeny analysis or by the dissection of females to determine the presence or absence of sperm. Ewing and Manning (1967) in their review of behavior genetics in insects single out a difficulty in the interpretation of Geer and Green's results. They argue that although Geer and Green demonstrate a relationship between pigment density and mating success it is not possible to attribute the disadvantage shown by the eye pigment mutants solely to that sensory defect. An alternative hypothesis is that the eye pigment mutations produce some pleiotropic effect in the animal's central nervous system which affects some aspect of the male's sexual behavior. Since the behavior of the mutants has not been examined in detail this remains a plausible hypothesis. These two alternative explanations may be examined by using the phenocopying technique described by Burnet et al. (1968).

Karyotype variation in Drosophila birchii.

Drosophila birchii, a member of the melanogaster species group of the subgenus Sophophora, is common in the tropical rain forests of the Australia-New Guinea areas. Chromosome squashes are easily prepared from the larval ganglion cells and the sex chromosomes are readily recognizable. The species exhibits a remarkable karyotype variation. The metaphase plate figures, in general, show two pairs of V's, one pair of dots and one pair of sex chromosomes. Variations in metaphase chromosome morphology are found in the X (with four types), the Y (with three types) and chromosome IV (with two types). Chromosomal interchanges between X- and Y-chromosomes Type I are postulated to be involved in the differentiation of sex chromosome morphology while the modification of chromosome IV seems likely to be a result of the acquisition of extra heterochromatin. These chromosome types form seven distinct metaphase plate figures, all encountered in wild populations, thus giving D. birchii the most variable karyotype in the genus Drosophila.

The Courtship Songs of Drosophila

Abstract1. The males of many Drosophila species perform wing displays during courtship and there is evidence that the stimuli provided by these is primarily acoustic. 2. The songs produced by members of the melanogaster and obscura species groups were recorded and analysed. 3. The songs consisted of regularly repeated pulses of sound. The frequency within the pulses and the interval between them varied between species but was constant and characteristic for each species. 4. It is suggested that the songs are codes which allow females to recognise con-specific mates.

THE EVOLUTIONARY STATUS OF DROSOPHILA SERRATA

One of the peculiarities of the genus Drosophila is the abundance in it of pairs, and of groups of several, sibling species. Siblings are species morphologically similar enough to be practically indistinguishable by inspection, and yet having attained complete or almost complete reproductive isolation. It is tempting to speculate that the evolution of morphological features has reached, in this genus, a high degree of perfection, and that the adaptive evolution is directed largely in physiological channels (Dobzhansky, 1956). Species being so often morphologically close, it is not surprising that geographic races of Drosophila species are as a general rule morphologically indistinguishable (cf. Patterson and Stone, 1952; see, however, Stalker and Carson, 1947, and Prevosti, 1954, 1955). In fact, the taxonomic category of subspecies has been seldom made use of in Drosophila, at least as compared to other groups of animals the systematics of which has achieved an advanced stage. In Drosophila, geographic populations, or races, of a species differ more often in such recondite traits as the gene arrangements in their chromosomes, which must, however, be regarded as connoting physiological differentiations. Instances of conspicuous variation in visible traits are, to be sure, known among Drosophila, but they usually represent intrapopulational balanced polymorphisms. The best studied case of this sort is the variation of the coloration of the abdomen in Drosophila polymorpha (da Cunha, 1949); the case of Drosophila montium is alleged to be similar (Freire-Maia, 1949), but the published data are inconclusive. Drosophila serrata Malloch (1927) is a species belonging to the melanogaster species group of the subgenus Sophophora, described from a locality (Eidsvold) in Queensland, Australia. A redescription, in the form now accepted in Drosophila systematics, can be found in Mather, 1955. We have collected strains belonging to this species from several localities in eastern Queensland, in New South Wales, in New Guinea, and New Britain. Two morphologically distinguishable subspecies can be recognized among these strains. Incipient reproductive isolation, particularly sexual isolation and some hybrid sterility, is also observed among these strains. Interestingly enough, the limits of the morphological subspecies do not coincide, however, with those of the reproductively isolated groups of populations. Observations and experiments bearing on the evolutionary status of this remarkable species are reported below.

Eye Pigment Relationships in Three Species Groups of Drosophila

The system of pigment cells in the com-pound eyes of Drosophila melanogaster has been described by Nolte (1950), Gersh (1952) and Clayton (1952). In these cells the pigment granules are laid down and they carry deposits of two pigment components, a red and a brown. These pigments can be extracted differentially (Ephrussi and Herold, 1944; Nolte, 1952); the red pigment is extracted in an acidified ethyl alcohol (AEA) and the brown pigment in acidified methyl alcohol (AMA). Quantitative estimations of the two pigments have been made by means of spectrophotometric analysis of the two extracts, and a comparison has been made between the wild type and a large number of mutant strains (Nolte, 1952-1955). In a later study (Nolte, 1958b) the degree of dominance of wild type alleles of various mutant eye-color genes was investigated, and quantitative data were included for two South African strains of D. melanogaster; these were found to differ greatly from the data for the Canton-S strain which had mainly been used as a basis for the quantitative comparison of mutant strains of this species. This fact led to a consideration of the status of this quantitative characteristic in the various species and strains of Drosophila in South Africa. Since it then appeared that these pigment measurements might be useful characters for the analysis of natural populations, and could possibly be of interest in the tracing of phylogenies, the investigation was extended to include foreign species and strains. Since it is possible that the melanogaster and willistoni species groups are directly derived from the obscura group (Sturtevant, 1940), the investigation was extended to include species and mutant strains of these three groups of the subgenus Sophophora.

The Influence of Light on the Mating Behavior of Seven Species of the Drosophila melanogaster Species Group

The Influence of Light on the Mating Behavior of Seven Species of the Drosophila melanogaster Species Group