The First Detection of Resistance to Phosphine in a Natural Population of the Rice Weevil Sitophilus oryzae (L.) (Coleoptera, Dryophthoridae) in Russia

In modern conditions, one of the most important tasks of the state is self-sufficiency in grain reserves. In this context, not least essential is the safety of grain while minimizing its losses and damage by insect pests. According to resent investigations results, one of the efficient means against pests of grain reserves is the phosphine gas. Phosphine has been widely used in Russia since the early 90s of the XX century. The article presents the study results on resistance to phosphine of the fusty flour beetle (Tribolium castaneum), larvae of the khapra beetle (Trogoderma granarium Ev.), imago of the wheat weevil (Sitophilus granaries L.) at every development stage. We have estimated a very close dependence of the mortality of Tribolium castaneum at any development stage in natural and laboratory populations on the concentration of phosphine. The Rostov population of the mace-eared crustacean is better resistant to phosphine than the laboratory population at any development stage. At the same time, imago of both laboratory and Rostov populations are not as resistant to the action of the insecticide as the egg stage. The study has identified a strong correlation between the mortality of active larvae in both natural and laboratory populations of Trogoderma granarium Ev. on one hand and the concentration of phosphine on the other. By the probit analysis results, the Petersburg population of active larvae of the khapra beetle is better resistant than the laboratory population, but their resistance will decrease as the exposure time increases. Experimentally studied and mathematically described is the dependence of adult mortality in natural and laboratory populations of Sitophilus granaries L. on the concentration of phosphine. The resistance index to phosphine in imago of the Stavropol, Krasnodar and Tambov populations is 1.5; 1.4 and 1.6, respectively.

Gene arrangement frequencies of different chromosome types of three inversions, IIL-2, III-35 and III-2 are reported in some natural and laboratory populations of Drosophila nasuta. In general, the frequencies of inversion heterozygotes for these inversions are in excess of what is expected under Hardy-Weinberg equilibrium in both natural and laboratory populations. This suggests that these inversion heterozygotes are heterotic to the species as far as viability is concerned. Similar to what occurs in the cosmopolitan species, chromosomes with standard gene sequences are more frequent than inverted gene sequences in this species. The scarcity of inversion homozygotes is due to reduced viability of their carriers, which probably have lethal or sublethal combinations of alleles in the inverted sections of their chromosomes. Further, the inversion frequencies in laboratory populations follow the frequencies in natural populations.

Thirteen laboratory populations (six mass cultures and seven isofemale lines) of Drosophila bipectinata were established from files collected from six different geographic localities (four in the north and two in the south) in India. These mass cultures and isofemale lines were maintained in food bottles in the laboratory for varying number of generations by transferring about 50 files (females and males in equal number) in each generation. After several generations, all the laboratory populations were analysed chromosomally to determine the frequency of different inversions. The results indicate that all the laboratory populations remained chromosomally polymorphic due to the persistence of inversions which were originally present ion the populations. The quantitative data on the frequency of inverted gene orders and the level of inversions heterozygosity in laboratory populations are compared with those in corresponding natural populations. This comparison clearly shows that there is a considerable increase in the frequency of inverted gene orders and the level of inversion heterozygosity in laboratory populations when compared with corresponding natural populations. This is most likely to be due to selective advantage of inversion heterozygotes under stringent competition in laboratory populations. Thus heterotic buffering is associated with chromosome inversion of Drosophila bipectinata.

The response of Rhyzopertha dominica and Sitophilus oryzae (both phosphine-resistant) in mixed-age cultures to phosphine at fixed concentration-time products (CT) of 10,500 to 168,000 microliters litre 1 h (ppm h) with either constant, rising or falling concentrations for 7 days was studied at 27 (+/- 2) degrees C. At lower CT products, rising concentrations of phosphine led to significantly fewer survivors of R dominica and S oryzae. Conversely, exposure to falling concentrations of phosphine resulted in significantly more survivors. The influence of changing concentrations of phosphine was more pronounced in S oryzae than in R dominica. In the latter, at the lower CT products of 21,000 and 42,000 microliters-1 h, the adult stage proved to be most tolerant, contrary to the accepted belief that the egg or pupal stage are always more tolerant to phosphine. The results indicate that application of phosphine in rising concentrations is more effective than in constant or falling concentrations.

Hermaphroditism is relatively common among coastal and reef-associated tropical marine fishes (Reinboth, 1970; Thresher, 1984; Sadovy and Shapiro, 1987). However, the western Atlantic mangrove killifish, Rivulus marmoratus, appears to be unique among hermaphrodites in its pattern of sexual allocation and reproduction. In laboratory populations, fish are reported to be either primary males that develop directly and produce only sperm, hermaphrodites that produce both sperm and ova, or secondary males that arise from hermaphrodites following loss of female function (Harrington 1975). In natural populations, primary males are reported to be rare (Harrington, 1975; but see Davis et al., 1990; Turner et al., 1992a), and secondary males have not been verified (Harrington, 1971). No pure females have been reported from either natural or laboratory populations (Harrington, 1975; Soto et al., 1992). On the basis of previous laboratory and field data, most individuals in this species are assumed to be obligate self-fertilizing hermaphrodites (Harrington, 1971; Davis et al., 1990; Soto et al., 1992). Results from studies of tissue transplants and allozymes confirmed this assumption (Harrington, 1975; Vrijenhoek, 1985). However, recent molecular studies (Turner et al., 1991, 1992b) have shown much richer genetic variation in natural populations of R. marmoratus than did earlier techniques. We examined gonadal development in R marmoratus to clarify the pattern of sexual allocation in this species and to confirm whether it is, in fact, an obligate selffertilizing species (Judson and Normark, 1996).

Population genetic variations of Helicoverpa armigera (Hiibner) over different major cotton growing regions were analyzed by DNA polymorphism amplified with four simple repetitive sequence primers. The results showed that the laboratory population had relatively lower genetic variation than natural populations. The genetic variation between natural populations was not significant and genetic variation existed in the same location from different years, indicating frequent migration among natural cotton bollworm populations. Cluster analysis indicated that individuals from Chaoyang of Liaoning Province (CY), Gaotang of Shandong Province (GT) and Dafeng of Jiangsu Province(DF) were more mixed each other, which suggested that CY population might have higher gene flow with GT and DF populations, especially with GT population. It supports the theory that the cotton bollworm in Northeast China came from Shandong and Hebei Provinces. This result also demonstrated that the molecular makers in this study are sensitive to detect population genetic structure changes.

Drosophila melanogaster from Australia, Europe and North America enter an adult ovarian dormancy in response to short days and low temperatures. The independent effects of temperature and day length in the determination of dormancy have been examined only in one long-established laboratory line (Canton-S). In all other studies of natural or laboratory populations, dormancy has been assessed at either a single short day or a single moderately low temperature. Herein, we determine the relative roles of temperature, photoperiod, and their interaction in the control of ovarian dormancy in D. melanogaster from two natural populations representing latitudinal extremes in eastern North America (Florida at 27 degrees N and Maine at 44 degrees N). In both natural populations, temperature is the main determinant of dormancy, alone explaining 67% of the total variation among replicate isofemale lines, whereas photoperiod has no significant effect. We conclude that ovarian dormancy in D. melanogaster is a temperature-initiated syndrome of winter-tolerant traits that represents an adaptive phenotypic plasticity in temperate seasonal environments.

Deterministic and stochastic evolutionary processes drive adaptation in natural populations. The strength of each component process is determined by the population size: deterministic components prevail in very large populations, while stochastic components are the driving mechanisms in small ones. Many natural populations, however, experience intermittent periods of growth, moving through states in which either stochastic or deterministic processes prevail. This growth is often countered by population bottlenecks, which abound in both natural and laboratory populations. Here we investigate how population bottlenecks shape the process of adaptation. We demonstrate that adaptive trajectories in populations experiencing regular bottlenecks can be naturally scaled in time units of generations; with this scaling the time courses of adaptation, fitness variance, and genetic diversity all become relatively insensitive to the timing of population bottlenecks, provided the bottleneck size exceeds a few thousand individuals. We also include analyses at the genotype level to investigate the impact of population bottlenecks on the predictability and distribution of evolutionary pathways. Irrespective of the timing of population bottlenecks, we find that predictability increases with population size. We also find that predictability of the adaptive pathways increases in increasingly rugged fitness landscapes. Overall, our work reveals that both the adaptation rate and the predictability of evolutionary trajectories are relatively robust to population bottlenecks.

In varying lemmings from seven natural populations (from Bolzhezemel'skaya tundra to Chukotka Peninsula), the number of B chromosomes ranged from 0 to 15. In populations surveyed for several years, B chromosome frequencies were stable. Two laboratory colonies (founded by Dicrostonyx torquatus from the Polar Urals and D. t. chionopaes from Yakutia) produced more than 3000 animals, of which 1699 were karyotyped. A small excess of B chromosomes in the progeny over that in their parents was observed in each generation. Coefficients of transmission k1 of additional chromosomes were on average 0.519 in D. t. torquatus and 0.511 in D. t. chionopaes. In oocytes I and II, an accumulation of B chromosomes was observed as compared to somatic cells (k2 = 0.66). The reproductive output of animals from both laboratory colonies did not depend on size of the B genome. The reduction of body and scull sizes observed in animals carrying numerous B chromosomes may confer negative selective value in the conditions of the Extreme North. In general, the system of B chromosomes in D. torquatus is well balanced and very stable, being apparently under strong genetic control.

The seemingly paradoxical increase of a species population size in response to an increase in its mortality rate has been observed in several continuous-time and discrete-time models. This phenomenon has been termed the "hydra effect". In light of the fact that there is almost no empirical evidence yet for hydra effects in natural and laboratory populations, we address the question whether the examples that have been put forward are exceptions, or whether hydra effects are in fact a common feature of a wide range of models. We first propose a rigorous definition of the hydra effect in population models. Our results show that hydra effects typically occur in the well-known Gause-type models whenever the system dynamics are cyclic. We discuss the apparent discrepancy between the lack of hydra effects in natural populations and their occurrence in this standard class of predator-prey models.

The frequency of chromosome damage was studied in the carriers of virus of the hemorrhagic fever with renal syndrome (Puumala virus) and in noninfected animals from two laboratory colonies and two natural populations of bank vole. In the laboratory colony, where Puumala virus persisted for three years, multiaberrant (“rogue”) cells were found in the bone marrow; the mean frequencies of both structural and numeral chromosome abnormalities were significantly enhanced. In the other laboratory colony, no Puumala virus was detected during all 30 years of its existence, but the mean frequencies of structural chromosome damage were increased to the same degree probably due to the prolonged breeding under laboratory conditions, which resulted in suppression of immunity and DNA repair. The voles from the natural populations were more resistant to the clastogenic viral effect, but they also had multiaberrant cells which served as indicators of viral infection. The data obtained support the hypothesis that viral infections increase mutation rate, contributing thereby to the evolution process.

Anastrepha fraterculus (Wied.) is known as the South American Fruit Fly. In order to develop efficient control strategies, we need deep knowledge on its biology along with periodical studies on population dynamics. Citogenetic studies on natural populations of this pest fly made it possible to reveal the presence of double minute chromosomes (DMs) in several natural populations of this insect. Cytogenetic studies performed in our insect laboratory, allowed the genetic analysis through a genealogical methodology. The establishment of families made it possible the genetic studies allowing the rigorous identification, characterization and confirmation of new chromosomal variants, frequently missinterpreted when the materials analyzed only come from nature. Double minute chromosomes -considered a type of chromosomal rearrangement- are extra chromosomal gene copies. This study sought to answer: What role do DMs chromosomes play in laboratory populations of the pest derived from natural populations? How are they transmitted from one generation to another? To answer our questions, we analyzed for 25 generations, two laboratory populations derived from Tucuman (T) and Buenos Aires (BA -tester) guava,. Data were recovered from cytological analysis of ganglia preparations revealed with H33258. The natural population from BA didn’t carry DMs. Results showed DMs in flies of both laboratory populations. DMs were transmitted from parents to progenies through 25 generations and their transmission was randomized in number. DMs are the cytological expression of resistance mechanisms used by the pest as a response to environmental stress. DMs in BA strain marked the change to the laboratory environment. A. fraterculus is a model insect for the study of cancer.

Adjustment of a population's gene pool to maintain maximum fitness is to be expected following changes either in selective forces, in genetic variability, or in both. New genetic combinations may evolve when genic complexes are derived from unrelated genomes as in laboratory populations of Drosophila with chromosomes of diverse origins (mesoevolution of Dobzhansky, 1954; Dobzhansky and Pavlovsky, 1957; Dobzhansky and Spassky, 1962). But the fact that no laboratory population is static and fixed in its genetic composition (except an isogenic strain) is demonstrated by the evolution of new adaptive complexes when natural selection has an opportunity to act on any genetic variation which has not yet attained equilibrium, even when that variation is a sample from a single welladapted natural population (Buzzati-Traverso, 1955; Lewontin, 1958; Strickberger, 1963). These experiments on laboratory populations derived from natural populations serve to illustrate clearly the dynamic poise of those populations and the rapid deterministic nature of the selective process in establishing new genetic equilibria. On the basis of laboratory population results from earlier work, Spiess (1961) described the outcome of gene arrangement frequency changes with strains of Drosophila persimilis from Timberline (10,000 feet elevation in the Yosemite area) as unexpected responses indicating the extreme novelty of population cage conditions for Timberline genotypes compared with the more expected responses of flies

The harlequin ladybird, Harmonia axyridis, is an important natural enemy of aphids throughout the world, but is now also considered an invasive alien species. We performed a meta-analysis of published life history data to address the question whether invading populations in Europe and North America have life history parameters that differ from native populations in Asia, explaining the beetle’s invasion success in new territories. In this meta-analysis, we accounted for important covariables that are often reported in published studies such as temperature, food source (aphids or eggs of Ephestia kuehniella), strain (laboratory or field populations) and photoperiod. Temperature was a key factor having consistent large effects on development rate, survival and reproductive characteristics of H. axyridis. Food source, strain, and photoperiod had effects on some, but not all characteristics, and their overall effect across characteristics was minor. Individuals of invasive populations had a shorter pre-oviposition period and higher fecundity at low temperatures than those of native populations, and a greater longevity across all temperatures. No differences in survival were found between native and invasive populations, while differences in development rate were not consistent, with opposing results obtained according to the way development rate was measured in trials reported in the literature. Results of this meta-analysis support the hypothesis that the life history of the beetle has changed during its invasion into North America and Europe. Invasive populations had a shorter pre-oviposition period and higher fecundity at low temperatures, as well as a greater longevity across all temperatures than native populations. These differences may partially explain the invasive success of H. axyridis.

The evolution of senescence in natural populations of guppies (Poecilia reticulata): a comparative approach.