J. Zool. Syst. Evol. Research zyxwvutsrqp 33 (1995) 84-87 zyxwvuts 0 1995 Blackwell Wissenschafts-Verlag,Berlin ISSN 0947-5745 Received zyx on 28 August 1994 zy Genetics Laboratory, Department zyxwvuts of Zoology, Utkal University, Bhubaneswar, India Abdominal pigmentation in Drosophila melanogaster females from natural Indian populations APARUP DAS Abstract Females of Drosophila melanogaster collected from five geographically distant populations in India were analysed for the intensity of pigmentation in the Sth, 6th and 7th segments of the abdomen. In all three segments, this intensity was found to vary among individuals of any given population, and, furthermore, different populations differ with respect to this phenotypic trait. Statistical analysis revealed significant intra- and interpopulational variation. zyxwvutsr A clinical pattern was detected: females from populations closer to the equator tended to have lighter cuticle, in which case differences between the three segments could not be detected and all three segments responded both independently and jointly to latitudinal variation, as indicated by a statistically significant positive correlation between latitude and pigmentation score. This is the first report on abdominal pigmentation analysis in natural populations of D. rnelanogasfer that provides evidence that phenotypic flexibility reflects temperature differences, as a result of which abdominal pigmentation shows geographic differentiation. Key words: zyxwvutsrqponmlk Drosophilu zyxwvutsrqp rnelanogasfer - abdominal pigmentation - Indian natural population Introduction Studies of population genetics provide fundamental infor- mation on the genetic structure of natural populations. Parallel studies of genetic and morphometric traits show the evol- utionary potential of the species. Differentiation may be a consequence of local adaptations or stochastic events such as founder effect and genetic drift. Drosophila is the favourite subject of evolutionary biologists trying to establish the struc- ture of a particular trait in different populations in different environments. Drosophila melanogaster has a worldwide dis- tribution. Different genetic and morphological traits have been studied and geographical differentiation in the form of parallel clines over different continents have been detected (David and Capy 1988). This may be taken as a powerful argument in favour of the adaptive differentiation model (Endler 1986). In natural populations of this species, several observations and arguments suggest that variation in body colour has some adaptive significance (David et al. 1983,1985; Payant 1986; Capy et al. 1988). Population-genetic studies of D. melanogaster have been initiated relatively recently in India. They have revealed a very interesting phenomenon: strong latitudinal clines for both the four cosmopolitan chromosome inversions (Das and Singh 1991; Singh and Das 1992) and ADH allozymes (Parkash and Shamina 1993) have been detected. Additionally, a non- adaptive latitudinal cline in the mating propensity of Indian D. nielunogaster and a reference strain of D. simulans have been observed (Das et al. 199s). Studies of hybrid dysgenesis of the P-M and I-R systems and tolerance to starvation and desiccation stress have recently been initiated, providing evi- dence that Indian 19. melanogaster is ancient and has evolved locally for a longcr time (A. Das unpubl. data). In this study, both intra- and interpopulational variations for the pigmentation polymorphism in the last three abdominal segments in females of Indian D. melanogaster were detected, as was clinal variation of the trait in proportion to the latitude of thc origin of the population samples. This study, although undertaken for the first time, provides evidence in support of i r’ /’ r -’-’ zyxwvu c. I e3 5. 8 . 0 , .o Fig. 1. Map of India showing the localities of the collection of 19. rnelanogastersamples: 1. Delhi; 2. Ahmedabad; 3. Indore; 4. Cuttack; 5. Renigunta results already obtained in experimental populations (Das el al. 1993, 1994) that temperature may be a major factor in determination of abdominal pigmentation in this species. Materials and methods Natural population samples of D. n~elur~ognsfrr were collected from five ecologically different and geographically distant places in India (Fig. I). These five places were chosen to cover a wide latitudinal range since it is known that ecological and temporal changes are associated with changing latitude. From each place, the flies wcrr collected by exposing fermented banana bait inside houses from I I S C opyriglit Clearrnce Center Code Statement 0947-5745/95/3302-0084$11 .oo/o