Differing amounts of genetic polymorphism in testes and male accessory glands ofDrosophila melanogaster andDrosophila simulans

We surveyed genetic polymorphism by two-dimensional gel electrophoresis of male reproductive tract proteins in 20 isofemale lines each ofDrosophila melanogaster andDrosophila simulans. After classifying 244 such proteins ofDrosophila melanogaster and 271 ofDrosophila simulans by their distribution between testes and accessory glands within the reproductive tract, significant correlations were found between genetic polymorphism and tissue distribution. In both species, gland-specific proteins were significantly more polymorphic than testis-specific proteins, as well as those found in both testes and glands. Simultaneously, inDrosophila simulans, proteins found in roughly equivalent relative abundance in both testes and glands were significantly less variable than gland-specific and testis-specific proteins, as well as those with a quantitative difference in relative abundance between testes and glands. These correlations may reflect general differences in variability between extracellular and intracellular proteins and between proteins with broad as opposed to tissue-specific distributions.We thank the Natural Sciences and Engineering Research Council of Canada for financial support (Grant A0235 to R.S.S.).     

On the relationship between the Bosmina taxa coregoni and thersites (Cladocera), as indicated by subfossil remains

A succession of morphs from Bosmina coregoni f. coregoni to B. c. f. thersites, which vary in shell and antennule characters, occurred in an undated 176 cm long sediment core from the Neversdorfer See (N. Germany).     

齿突蟾属某些种的多态现象

本文报道某些锄足蟾科Pelobatidae动物的多态现象。讨论了同域或不同域的四种齿突蟾Scuti-ger,即刺胸齿突蟾S. mammatus(Guenther)、胸腺齿突蟾S. glandulatus(Liu)、木里齿突蟾S. mulicnsis Fei et Ye和皱纹齿突蟾S. ruginosus Zhao et jiang的皮肤瘰疣、第二性征等性状;用薄层等电聚焦电泳方法分析了同域三种齿突蟾的晶体蛋白。结果表明:前三种是有效种;后一种,即皱纹齿突蟾分别是前三种的多态性变体;这些变体以相同性状(即皮肤多瘭疣)同时表现在三个种中的现象,属于平行多态现象。     

Enzyme polymorphism in Drosophila melanogaster populations in Iraq

Electrophoretic studies of the degree and pattern of polymorphism at two third-chromosome loci, esterase-6 (Est-6) and phosphoglucomutase (PGM), were carried out in three Drosophila melanogaster populations collected from different localities in Iraq: Mosul, Tuwaitha, and Basrah. The results show that only the Tuwaitha population was polymorphic for both loci; the other two populations were polymorphic for Est-6 and monomorphic for PGM. The allele frequency changes at both loci were followed for 20 generations in an experimental cage derived from the Tuwaitha population; it was found that there is a deviation from Hardy-Weinberg equilibrium at both loci toward the homozygote.     

Polymorphism at the Hor 1 locus of barley (Hordeum vulgare L.)

The Hor 1 locus of barley encodes a group of seed storage polypeptides called C hordein. Two-dimensional electrophoretic analysis of C-hordein fractions from six cultivars with different alleles at the Hor 1 locus showed extensive polymorphism. A total of 34 major polypeptides was mapped, with between 4 and 18 present in each cultivar. There was less variation among the same cultivars in the numbers (6 to 10) of restriction fragments of genomic DNA which hybridized to a cDNA clone related to C hordein. The total number of restriction fragments was also lower (22), and most pairs of cultivars had more restriction fragments than polypeptides in common. A total number of about 20–30 C-hordein genes per haploid genome was estimated. The results indicate that cultivars differ mainly in the extent of gene and polypeptide divergence, rather than in the degree of gene reiteration. They are consistent with the proposed origin of the multiple structural genes at the Hor 1 locus by the duplication and divergence of a single ancestral gene.NACB was supported by a grant from the Home Grown Cereals Authority.     

A linkage study of protein-coding loci in Macaca mulatta and Macaca fascicularis

Genealogical and gene marker data from the closely related species Macaca mulatta and Macaca fascicularis have been used to search for linkage between genes coding for the blood proteins albumin, carbonic anhydrase 1 and 2, diaphorase 1 and 2, group-specific component, glucose phosphate isomerase, hemoglobin alpha chains, isocitrate dehydrogenase, prealbumin, and transferrin. The results are consistent with conservation of the linkage between the loci coding for albumin and group-specific component and loci coding for the two carbonic anhydrase isozymes, as observed in other species. Among the 38 possible pairwise comparisons, no new linkage groups were identified. Tight linkage can be excluded for most pairs of loci.     

Differential winter mortality and seasonal selection in the polymorphic ladybird Adalia bipunctata (L) in the Netherlands

Seasonal selection acting on the melanic polymorphism in the two-spot ladybird Adalia bipunctata was investigated in The Netherlands. An increase in melanic frequency over the spring-summer reproductive period was quantified. The selective advantage gained by melanics averaged 9%, but significant heterogeneity occurred between populations. Adult hibernation behaviour is described. The beetles when outdoors show a highly clumped distribution both between and within trees. The distribution of the morph classes between aggregations is random. Survivorship in a hibernating cohort (initial n= 1898) on a grid of 70 lime trees near Utrecht was monitored by making three counts over the winter of 1981–1982. Intense selection favouring each melanic morph occurred during December and January. The relative fitness of non-melanics was 0.55 (melanics =1). The discovery of dead beetles in late January (about 5% of total losses) and the absence of spatially density-dependent mortality were consistent with a climatic stress rather than selective predation. The period of selection was associated with very cold temperatures averaging up to 4°C below normal and an overall mortality of nearly 75%. There was no change in morph frequency, near normal temperatures and a lower mortality from February to early April. Examination of groups of nearby trees in late January strongly suggested that similar differential mortality had occurred except on some willows. This difference was probably due to the more protected hibernation sites available on these trees. Samples of hibernating cohorts at three other sites showed no evidence of differential mortality. Laboratory experiments with hibernating beetles found no difference in survivorship or rate of weight loss between starved non-melanics and melanics in temperature regimes with and without periods of adult activity. It is concluded that the intense winter selection on the study limes is probably exceptional. Examination of changes in morph frequency through the annual cycle suggests that at some sites the selection favouring melanics during reproduction is counterbalanced by selection against melanics in late summer or early autumn. The results are discussed in relation to mathematical models of cyclical selection and to other field studies including that of Timoféeff-Ressovsky (1940), who found large decreases in melanic frequency during hibernation in Berlin.     

Immigration of the brown planthopper, Nilaparvata lugens, exhibiting various responses to density in relation to wing morphism

Considerable inherent variations in the relation between macropterous and brachypterous wing forms, and nymphal density were found in field populations of the brown planthopper, Nilaparvata lugens Stål (Homoptera: Delphacidae), collected from various locations in Japan. When compared under uniform laboratory rearing conditions, most of the female populations exhibited higher ratios of macropters with increasing nymphal density, but some showed extremely high proportion of brachypters and the others were highly macropterous, over broad ranges of density. These results indicate the possibility that the planthoppers in Japan, which are known not to persist in winter, are derived from different migration sources.About ten generations of successive selection for brachyptery from a population showing usual density-dependent wing morphism generated populations similar to highly brachypterous ones mentioned above. Genetic analysis of the inheritance of wing morphism revealed that brachyptery in the females was controlled by a single pair of dominant alleles. However, in the males wing forms did not segregate so clearly in the crossing experiments. This suggests that wing morphism in N. lugens in under sex-limited inheritance.

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Einwanderung von Nilaparvata lugens mit unterscheidlicher Reaktion auf Populationsdischte bei der Flügelausbildung

Zusammenfassung In Feldpopulationen von Nilaparvata lugens Stål., welche in verschiedenen Regionen Japans gesammelt wurden, bestand in der Beziehung zwischen makropteren bzw. brachypteren Flügelformen und der Larvendichte eine beträchtliche Variation. Unter einheitlichen Zuchtbedingungen im Laboratorium stieg der Makropterenanteil bei den meisten Weibchenpopulationen mit steigender Temperatur; bei einigen Populationen hingegen war entweder der Brachypterenanteil oder der Makropterenanteil extrem hoch und zwar über weite Dichtebereiche. Dies deutet auf die Möglichkeit hin, dass die Zikade in Japan, wo sie bekanntlich nicht überwintert, jeweils aus verschiedenen Quellen einwandert.Wenn eine Population mit der üblichen dichteabhängigen Flügelausbildung 10 Generationen lang auf Brachypterie selektioniert wurde, entstanden Populationen, die den erwähnten hochbrachypteren Populationen aus dem Feld glichen. Die genetische Analyse der Vererbung der Brachypterie ergab, dass bei Weibchen ein einzelnes dominantes Allel verantwortlich ist. Bei Männchen dagegen trennten sich bei Kreuzungsexperimenten die Flügelformen nicht so klar. Dies deuted auf Unterschiede zwischen den Geschlechtern bei der Vererbung der Flügelformen.

     

Temporal variation of allele frequencies in populations of Akodon dolores (Rodentia,Cricetidae)

Summary Six population samples of the South American cricetid rodent Akodon dolores were collected at the same site at six-month intervals over a three year period. Changes in density were detected. Seven out of 18 loci analyzed by means of starch gel electrophoresis were polymorphic. Only two of these loci (Est-4 and G6pdh) showed statistically significant variation in allele frequencies following a seasonal pattern. There was no correlation between allele frequencies and population density. When animals were grouped into two classes according to body weight, a clear difference in allele distribution at the Est-4 and G6pdh loci was observed between individuals 39 g or less and those heavier than 39 g. As the first group comprises predominantly younger animals, the data indicate that changes in the age-structure of population, rather than density variations, are responsible for the cyclic pattern of allele frequencies fluctuations.