Segregational Load in Drosophila Kikjsawai. 111
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SEGREGATIONAL LOAD IN DROSOPHILA KIKJSAWAI. 111. NATURAL POPULATIONS1 NEWTON FREIRE-MAIA AND ADEMAR FREIRE-MAIA2 Laboratdrio de Gendtica Humana, Faculdade de Filosofia, Universidade do Parana, Curitiba, Pr, Brasil Received April 24, 1964 ATURAL populations of D.kikkawai Burla (previously cited as D.montium NdeMeijere) present three different types of polymorphism: (1) a polymor- phism (associated with a sexual dimorphism) involving color and pattern of abdominal tergites; (2) a chromosomal polymorphism expressed in a long para- centric inversion in the left arm of chromosome 11; (3) a chromosome hetero- morphism in consequence of the mitotic chromosome IV being found both as metacentric and as acrocentric. With respect to color and pattern of abdominal tergites, two genetically pure forms (light and dark) have been isolated. Crossing experiments showed that a single pair of autosomal alleles is mainly responsible for the differences between them, with dark pigmentation dominant. The two color forms are easily distin- guished among females, but with difficulty among males. (For data, see FREIRE- MAIA1964a,b.) In this paper, data on the color polymorphism and on the inversion polymor- phism in natural populations will be presented and discussed. The problem of the chromosome heteromorphism will be only briefly touched, since no quantita- tive information was obtained concerning it. MATERIALS AND METHODS Domestic populations of Drosophila have betn survcyzd fr3m Buenos Aires. Argentina, to northeastern and nsrthern Brazilian localities. In a number of these places, D.kikkauai either was not found or was present with extremely low frequency. The localities where this species has been found are shown in Figure 1. The populations were sampled during about 11 years (1947-1957.). The majority of the collections have been made, however, during the period 1951-1957. Collections of the flies were made in markets, orchards, fruit deposits, etc. using an entomological net with a narrow end. No artificial “bait” has been used. The flies have been analysed in three different ways, using: (1) collected females; (2) cross- ings of collected males to light females from laboratory strains; and (3) the offspring of females inseminated in nature. For the analysis of chromosomes, preparations by the usual orcein method have been used. The vials with flies were kept at about 25°C. Quantitative data were obtained Dedicated to Dn. HARRYM. MILLER,JR., ex-director of the Rockefeller Foundation, in recognition of his outstanding contribution to the development of genetics in Brazil. This research has been made under grants from the Rockefeller Foundation, the National Research Council of Brazil, the National Nuclear Energy Commission of Brazil, and the Re- search Council of the University of Parani. ‘ Present address. Faculdade de CiBncias MQdicas e Biol6gicas, Botucatu, SP, Brasil. Genetics 50: 789-802 h-ovember 1964 790 N. FREIRE-MAIA AND A. FREIRE-MAIA FIGURE1.-Map of Brazil showing the localities where collections have been made. 1. Porto Alegre; 2. Florian6polis; 3. Ascurra; 4. Blumenau; 5. Gaspar; 6. Itajai; 7. Joinville; 8. Para- nag&; 9. Morretes; 10. Antonina; 11. Curitiba; 12. Irati; 13. Londrina; 14. Santos; 15. s. Paulo; 16. Campinas; 17. Assis; 18. Presidente Prudente; 19. Lins; 20. Belo Horizonte; 21. GoiCnia; 22. Salvador. through the analysis of only one larva from each female captured in nature. Nonfertilized or sterile females were discarded. RESULTS Color polymorphism-The data. Method I: Table 1 presents the results of a number of samples collected in different localities as analysed by Method 1 (direct examination of females) during the period 1947-1957. Statistical analysis of the comparisons among the different collections within the same locality revealed that the only one showing a significant difference (with P close to the 0.05 level) is ParanaguA. The only collection departing from the mean frequency 0.57 is that made in September 1952, with 0.67 light females (x2= 6.34; P between 0.01 and 0.02). The value of x2 for the 16 groups of data shown in Table 1 is 167.77 (d.f. = 15; P<O.OOl ) . It is clearly seen that this high heterogeneity is mainly due to the fact that the frequencies of light females are consistently lower in the southmost POLYMORPHISM IN D.kikkawai 791 TABLE 1 Frequencies of light females in different Brazilian localities I,11cahtv Time n* Light females Light females (Total)+ Porto Alegre, RGS Febr. '55 61 0.74 F 0.06 0.76 t 0.05 Florianbpolis. SC July '54 27 0.63 * 0.09 SeDt. '55 41 0.54 f 0.08 0.58 f 0.06 Itajai, SC Juiy '54 63 0.62 f 0.06 Febr. '56 62 0.71 i 0.06 Jan.-March '57 27 0.74 i- 0.08 0.67 i 0.04 Gaspar. SC June '52 14 0.43 i 0.13 Jan.-March '57 12 0.42 F 0.14 0.56 f 0.08 Ascurra, SC July '54 12 0.92 t 0.08 Oct. '55 16 0.69 t 0.12 March '57 4.5 0.53 +_ 0.07 0.64 k 0.05 Blumenau. SC Febr. '56 24 0.67 F 0.10 Dec. '56 23 0.65 t 0.10 March '57 26 0.69 f 0.09 0.69 t 0.05 Paranagui, Pr March '52 13 0.62 t 0.13 Sept. '52 148 0.67 F 0.04 Oct. '53 14 0.43 t 0.13 Sept. '54 25 0.60 * 0.10 Oct. '54 139 0.50 k 0.04 Nov. '55 24 0.58 F 0.10 Dec. '56 111 0.50 -C 0.05 0.57 F 0.02 Morretes. Pr March '47 33 0.94 F 0.04 Apr.-July '51 16 0.94 i 0.06 Sept.-Oct. '51 37 0.81 i 0.06 Nov.-Dec. '51 42 0.86 F 0.05 Aug. '53 22 0.77 F 0.09 Oct. '53 17 0.88 t 0.08 April '54 72 0.89 i. 0.04 Sept. '54 47 0.79 t 0.06 Oct. '54 191 0.90 t 0.02 Nov.'55 21 1.oo 0.88 t 0.01 Antonina, Pr Nov. '51 26 0.92 t 0.05 0.91 t 0.05 Londrina, Pr Sept. '54 16 0.88 F 0.08 0.85 t 0.08 S. Paulo, SP June '47 168 0.76 t 0.03 March '49 73 0.86 i 0.04 June-July '49 46 0.87 f 0.05 May '54 20 0.75 i 0.10 0.80 F 0.02 Presidente Prudente. SP July '56 13 0.69 F 0.13 0.69 i 0.13 Lins, SP April-May '54 46 0.89 k 0.05 0.89 i 0.05 Belo Horizonte, MG Aug.-Sept. '53 26 0.81 & 0.08 0.81 t 0.08 Goibnia, Go Sept. '53 25 0.84 k 0.07 0.84 * 0.07 Others$ - 10 0.90 t 0.09 0.90 f 0.09 * n is the t,,tal n~m111erof females. Only the samples with n > 10 are given. -IUnder tlir heading "Light females (Total),'' the frequencies of light females in the total of the siiniplt~collected in each localit)-. including those with n < 10. are given. $ "Others' lnclnde Curitiba (Pr). Irati (Pr), Santos (SP), Assis (SP), and Salvador (Ba). Collections in these locali- ties h.i\r hwn made in July 1951. April 1952, December 1954. September 1954. and Februarv 1954. respectively. RGS-Rco Gianrle do SUI; SC-Santa Catarina; Pr-ParanB; SP- Sdo Paulo; RIG-&has Gerais; Go-GoiBs. localities (from Porto Alegre to ParanaguA) than in the other ones (from Mor- retes in the South to Salvador in the East and Goidnia in the Center-West) (ex- cepting the small sample of Presidente Prudente). When comparison is made among the seven southmost localities (here called group A) and among the other ones (group B), the values of xz are respectively 16.91 (d.f. = 6; P+O.Ol) and 14.96 (d.f. = 8; P>0.05). The data from Porto Alegre contribute with a x2 equal to 6.55 to the value of 16.91. A reanalysis of group A without the data from Porto Alegre led to a x2 equal to 9.70 (d.f. = 5; P>0.05). It may be said therefore that 792 N. FREIRE-MAIA AND A. FREIRE-MAIA the Porto Alegre data are an exception within group A, characterized by a mean frequency of light females around 0.60. The whole group B, with a mean fre- quency of light females around 0.85, could be accepted as a relatively homogenous one. The total frequency of light females in S. Paulo (0.80) may be considered, however, as a law one on the basis of its own individual value of x2 (6.73; P<O.Ol). An analysis of group B with the exclusion of S. Paulo led to a x2 equal to 5.92 (d.f. = 7; P>0.50). The local data with larger number of collections--i.e., those from Paranagui, Morretes and S. Paulo-have been classified according to month of collection. Only the data from Paranagui show some suggestion of heterogeneity, significant at the 0.05 level. The data from Table 1 have also been classified according to the month of collection, irrespective of locality, in both groups A and B (Table 2). Since information is either lacking in some months or is based on only a few flies in others, these data have been pooled to form three-month classes, either includ- ing or excluding the data from two localities which seem to form exceptions in their respective groups, namely Porto Alegre in group A and S.