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Historically, subsistence farmers around the Atlantic coast of NW Europe utilized marine algae as a fertilizer in agroecosystems, a practice that continued in small areas and is now considered to have real potential for re-establishing sustainable food production systems on marginal soils. Earthworms form a significant component of soil fauna, and their ecosystem services are well-documented. Therefore, palatability of marine organic amendments to faunal detritivores of terrestrial systems is of interest. This work aimed to assess the potential for growth of Aporrectodea caliginosa, Lumbricus rubellus and Aporrectodea longa fed with two common macroalgae (seaweeds), Laminaria digitata and Fucus serratus. In addition, choice chambers were constructed to permit earthworm selection of these macroalgae with more conventional organic materials, horse manure (HM) and birch leaves (BL). Over a period of 2 months, earthworm species showed significantly greater mass gain with conventional food (p Laminaria outperformed Fucus, which in turn was superior to soil alone. Similarly, when given a choice, a significant preference (p A. caliginosa when offered seaweeds only. By contrast, L. rubellus and A. longa showed significant preferences (p Laminaria over Fucus and fresh material over degraded. These results underline an interest to profit from natural resources (seaweeds) to maintain or improve soil biological quality in marginal coastal areas.

In vitro selection combined with high-throughput sequencing is a powerful experimental approach with broad application in the engineering and characterization of RNA molecules. Diverse pools of starting sequences used for selection are often flanked by fixed sequences used as primer binding sites. These low diversity regions often lead to data loss from complications with Illumina image processing algorithms. A common method to alleviate this problem is the addition of fragmented bacteriophage PhiX genome, which improves sequence quality but sacrifices a portion of usable sequencing reads. An alternative approach is to insert nucleotides of variable length and composition ("phased inserts") at the beginning of each molecule when adding sequencing adaptors. This approach preserves read depth but reduces the length of each read. Here, we test the ability of phased inserts to replace PhiX in a low-diversity sample generated for a high-throughput sequencing based ribozyme activity screen. We designed a pool of 4096 RNA sequence variants of the self-cleaving twister ribozyme from Oryza sativa. For each unique sequence, we determined the fraction of ribozyme cleaved during in vitro transcription via deep sequencing on an Illumina MiSeq. We found that libraries with the phased inserts produced high-quality sequence data without the addition of PhiX. We found good agreement between previously published data on twister ribozyme variants and our data produced with phased inserts even when PhiX was omitted. We conclude that phased inserts can be implemented following in vitro selection experiments to reduce or eliminate the use of PhiX and maximize read depth.

Bacteria possess a range of mechanisms to move in different environments, and these mechanisms have important direct and correlated impacts on the virulence of opportunistic pathogens. Bacteria use two surface organelles to facilitate motility: a single polar flagellum, and type IV pili, enabling swimming in aqueous habitats and twitching along hard surfaces, respectively. Here, we address whether there are trade-offs between these motility mechanisms, and hence whether different environments could select for altered motility. We experimentally evolved initially isogenic Pseudomonas aeruginosa under conditions that favored the different types of motility, and found evidence for a trade-off mediated by antagonistic pleiotropy between swimming and twitching. Moreover, changes in motility resulted in correlated changes in other behaviors, including biofilm formation and growth within an insect host. This suggests environmental origins of a particular motile opportunistic pathogen could predictably influence motility and virulence.

Population cage experiments were employed to detect variability in fitness among Cry2Ab resistant and Cry2Ab susceptible genotypes of Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae). In two experiments, reciprocal crosses between a Cry2Ab resistant colony (SP15) and a susceptible colony (GR) established populations where the frequency of the allele that conferred resistance was 0.5. Experimental populations were then maintained without exposure to Cry toxins. At the F2 generation and on later occasions, the pooled egg output from each population was sampled, and emerging neonate larvae were screened to monitor the frequency of the resistant allele. Resistance is recessive so homozygous resistant insects could be readily identified as they are the only genotype to survive and grow when exposed to a discriminating concentration of Cry2Ab toxin. Assuming Hardy—Weinberg equilibrium after the F1 generation, and the persistence of a 1:1 ratio of resistant and susceptible alleles, one quarter of ...

A complex substrate consisting of fly ash, coal gangue and excess sludge was used as an experimental soil in pot culture experiments. Different soil compositions were tested by observing the growth of arbuscular mycorrhizal (AM) fungi inoculated white clover, rye grass or corn. The biomass of the host plants, the mycorrhizal colonization (MC) rate and the mycorrhizal dependency (MD) were measured. The research addresses the preferable AMF-plant-substrate combination appropriate for restoration of coal mines. We used two inoculation methods: single-inoculation with Glomus versiforme or Glomus mosseae and a dual inoculation with both G.v and G.m. The results show that G.m is the preferable fungi and that dual inoculation does not show advantages for the restoration of coal mines. White clover inoculated with AM fungi is the most suitable condition for restoration of coal mines. The best weight ratio of fly ash, coal gangue and excess sludge was found to be 20:60:20. The optimum treatment conditions of AMF-plant-activated-substrate are described.

A two generation selection experiment in Nile tilapia ( O. niloticus , Lake Manzala, Egypt) was carried out to test whether the proportion of males after temperature treatment could be sustainably influenced by selection. Starting with 45 families as a base population the families were tested for their thermal sensitivity in the following way. After a 9-day incubation period at 28 °C, fry of each family were subdivided into a control (28 °C) and a treatment group, each consisting of 110 fish. The treatment group was kept at a temperature of 36 °C for 10 days. Thereafter treated fry were gradually adapted to 28 °C again. Each treatment and corresponding control group was raised separately until sexing (by microscopic inspection of gonad squashes at a minimum age of 90 days). A random sample of ten males and females from control groups of each family was kept for later selection decisions. The percentage of males in treatment groups was the selection criterion and the families showing more than 80% males or less than 60% after temperature treatment were selected. Over two generations (G0 and G1) around 14% of the tested families were selected to produce two divergent lines ( high and low line) which showed a high or low response to temperature treatment regarding their sex ratios. In the first and second generation of selection 66 and 26 families were tested in the high line and 72 and 13 families in the low line, respectively. After two generations of selection the temperature treated groups in the high line showed a male percentage of 90%, whereas the weakly sensitive low line showed an average male proportion of 54%. The realized heritability estimated from the cumulated realized selection response and -differential in successive generations was 0.69 in the high line and 0.86 in the low line. This study provides the first evidence that a surplus of males in temperature treated groups can be selected for as a quantitative trait. Thus, temperature sensitive lines could be produced as a consumer- and environment-friendly approach to significantly increase the proportion of males in Nile tilapia, if large numbers of broodstock could be tested.

柑橘園におけるミカンハダニのヘキシチアゾクス抵抗性発達の様相を把握し, 抵抗性対策を考えるため, 静岡県榛原郡の日本曹達株式会社榛原農業研究所内の24樹からなる柑橘園において淘汰試験を行なった. 6年間で18回のヘキシチアゾクス連用散布 (25ppm) で, LC50値が8000ppm以上の高いレベルに抵抗性が発達した. 連続散布という特殊な処理体系でありながら抵抗性発達速度は遅かった. 最初の4年間は年2～3回の散布でミカンハダニの密度抑制が可能であったが, 次の2年間では効果が低下し年4回もの散布を必要とした. また, 同一園内でも樹ごとにミカンハダニの発生密度が異なるだけでなく, ヘキシチアゾクスに対する感受性も異なり, ヘキシチアゾクス抵抗性は, 特定の樹に寄生するミカンハダニの集団で局所的に発達したと考えられた.

A research program in salmon ranching in Iceland was started in 1987. The primary aim was to study genetic variation in return frequency to the site of release of smolts. Results from the freshwater period are presented. Broodstock of Atlantic salmon (Salmo salar) were taken from five stocks in Iceland in 1987 and 1988. Families were made by using semen from one male to fertilize eggs from three females. After fertilization, the eggs from each family were reared in separate egg trays. At startfeeding, each family was reared in separate tanks, using a total of 298 families. Survival was recorded for each family from eyed-egg stage until 12 weeks after startfeeding. Individual weight and length was recorded on a sample of fish from each family 190 days from the beginning of the startfeeding period. Significant differences (P

Laboratory selection experiments using Drosophila, and other organisms, are widely used in experimental biology. In particular, such experiments on D. melanogaster life history and stress-related traits have been instrumental in developing the emerging field of experimental evolution. However, similar selection experiments often produce inconsistent correlated responses to selection. Unfortunately, selection experiments are vulnerable to artifacts that are difficult to control. In spite of these problems, selection experiments are a valuable research tool and can contribute to our understanding of evolution in natural populations.

In a case study with red alder (Alnus rubra Bong.) we develop multiple breeding populations to cope with uncertainty in the response of genotypes to environmental changes. Genetic parameters and geographic variation in adaptive traits were studied to tailor breeding populations to specific climatic environments. Orthogonal clines were identified in bud break and growth cessation with spatial statistical analysis, implying that it is not possible to cope with effects of climatic warming by simply shifting provenances to new locations. Instead climatic warming may require the development of genotypes with novel combinations in adaptive traits. Selection targets for bud break and leaf abscission for six breeding populations were derived that cover current and possible future climatic conditions. Genetic parameters for adaptive traits were estimated, and it was confirmed that selection targets for the proposed breeding populations could be met in one generation. Heritabilities for the date of bud break and leaf abscission were moderately high (0.41 to 0.54) and genetic correlations implied that selection for advanced bud break and delayed growth cessation will positively influence growth traits.

Laboratory experiments with a rock-dwelling nocturnal gecko, Oedura lesueurii, showed that retreat-site selection (and other behaviours) are affected by the interplay between thermal benefits, social advantages and avoidance of predators. Velvet geckos were highly selective in habitat choice: they preferred artificial retreat-sites that mimic the thermal properties of natural rocks in full sun rather than those that mimic rocks in full shade; mature male geckos rarely shared retreat-sites with other adult males; and these lizards strongly avoided retreat-sites covered with the scent of a natural predator (the broadheaded snake, Hoplocephalus bungaroides). After documenting these preferences, we carried out additional trials in which two or more of these factors co-occurred, as is often the case in nature. Social dominance interacted with thermal benefits in determining retreat-site selection, with smaller (subordinate) males forced to use cooler retreat-sites when larger (dominant) males were present. Avoidance of predators was a higher priority than thermoregulation: the lizards would forego a warmer retreat-site with predator scent in favour of a cooler, unscented one. There was also an interplay between social dominance and predator scent: smaller males were forced to use either predator-scented retreat-sites or no retreat-site when larger males were present. General activity levels, and the frequencies of specific behavioural acts, also shifted in response to social and predator-scent cues. Our study emphasizes the complexity of habitat-selection behaviour in these lizards, and clarifies the criteria used in retreat-site selection when (as is commonly the case) the animal must choose between conflicting priorities. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.

Two types of small-scale selection experiments were performed. (1) Artificial selection experiments were performed on age-specific female fecundity. Selection for early fecundity over three generations produced a statistically detectable direct response. There was no detectable indirect response in other life-history characters. Selection for late fecundity over three generations did not produce any detectable direct response. Indirect responses were detected: early egg-laying decreased and longevity increased. (2) Natural selection for late-age fitness components increased late fecundity, female longevity, and the duration of female reproduction, while early fecundity and mean egg-laying rate decreased.

Atlantic salmon ( Salmo salar ) brood stock were taken from 32 strains in Norway for 3 consecutive years. Each year, after fertilization, the offspring in each family from each strain were reared in separate egg trays and fingerling tanks. Individual weights and lengths were recorded on a sample of fish from each tank. Environmental and genetic factors influencing the growth rate were studied. The length and weight at a standardized age were significantly affected by hatching date and number of fish held in a tank. There was also a significant ‘tank effect’ which influenced the heritabilities estimated. Significant differences between strains were found for all three year-classes ( P

Salmon (Salmo salar) brood stock were taken from 37 localities in Norway for 4 consecutive years. Each year, after fertilization, the offspring in each family from each strain were reared in separate egg trays and fingerling tanks. The percentage of fish in each tank which smoltified at 1 year old was recorded, and environmental and genetic factors influencing the percentage smoltification were studied. Percentage smoltification was significantly affected by the number of fish held in a tank, or fish density (correlation coefficient 0.03–0.27). Variation between locality of origin of brood stock and per cent smoltification was highly significant for each year class, and there was a high correlation (0.89–0.95) between smolt percentage and average weight of fish in a family. Heritabilities in per cent smoltification estimated by sire component from total data had a weighted average of 0.06 (range 0.16 to −0.01). From the dam component heritabilities ranged from 0.20 to 0.40 when tank effect was ignored, and 0.08–0.25 with tank effect taken into account. Variance components for locality were two to three times as high as those for sires within localities, indicating that genetic variation is greater between than within localities. Highly significant interaction sire × dam was found, suggesting a considerable nonadditive genetic variance influencing the percentage of fish smoltifying at 1 year of age.

This paper reviews (i) basic studies on the genetics of symbiosis in red clover (a self-sterile species) and subterranean clover (cleistogamous) and (ii) work on selection and plant breeding to increase nitrogen fixation in these hosts. Symbiotic effectiveness in red clover is influenced by many major and minor genes. The highly effective phenotype is inherited in a complex manner associated with early nodulation and the formation of large amounts of persistent bacteroid-containing tissue. Lines bred to fix more nitrogen with one strain ofRhizobium trifolii do so with most but not all other strains examined. They also show slightly increased vigour when grown on nitrate. The highly effective response is correlated with abundant nodulation and an early flowering habit, the evidence from breeding studies indicating that this correlation is not absolute. Normally effective and highly effective nodules have the same specific nitrogenase activities. The expression of the highly effective response is relatively little affected by environmental factors (temperature, light intensity, day length, supplementary carbon-di-oxide). Inbreeding substantially degrades the symbiotic response. Heterosis is shown in crosses between cultivars of subterranean clover but otherwise selection to increase effectiveness in this host was unsuccessful. The relevance of these results (and their physiological aspects) for the improvement of grain legumes is discussed.

Disruptive selection with negative assortative mating as well as with opportunity for random mating was carried out for sternopleural bristles in Drosophila melanogaster. In the latter system, the divergence in score between the progeny of high and low females altered little after the fifth generation and was, at the end of 14 generations, much less than expected theoretically. An explanation is suggested for this result, which is paralleled by those of several other workers, in terms of the mating behavior of the females.

The kangaroo rat, Dipodomys merriami, occurs with the pocket mouse, Perognathus penicillatus, in stands of mesquite with little herbaceous cover. The dipo avoids areas that have thick cover between 8 cm and 45 cm. The pocket mouse prefers areas that have considerable cover over 45 cm. Those facts have been established both by previous studies and those reported here. This paper reports the results of altering the vegetation in small patches of land and observing concomitant changes in the land—use patterns of the rodents. The difference between the species appears to be crucial to their coexistence.

The research facilities at the fish experimental station at Sunndalsora are described. The design of a selection experiment with salmon and sea trout is presented. The station is also used for other purposes, such as investigations into nutrition, pathology and environmental factors. In this paper analyses of observed differences to vibrio disease ( Vibrio anguillarum ) are reported. Significant differences in resistance between river strains of salmon parr were found. The difference between localities are supposed to be partly heritable. The data were also used to estimate the heritability on an intra-river basis. The estimates were 0.12 and 0.07 based on the sire and dam component, respectively. It is concluded that selection against vibrio disease will result in genetic change.

By using a colorimetric method developed by LOWRY et al. (1951), sericin content in cocoon filament was determined and a selection experiment has been carried out toward both direction of high and low values. Moths from cocoons showing either high or low absorbance at 500 mμ (A500) were bred for further selection in successive 5 generations. In G5 the A500 values were significantly different between the high and low lines. Scouring off ratio in the cocoon filament responded in the same way. In the low line both the weight of the cocoon and of the cocoon shell decreased as selection proceeded.

Alcoholic fermentation is fundamentally an adaptation process, in which the yeast Saccharomyces cerevisiae outperforms its competitors and takes over the fermentation process itself. Although wine yeast strains appear to be adapted to the stressful conditions of alcoholic fermentation, nitrogen limitations in grape must cause stuck or slow fermentations, generating significant economic losses for the wine industry. One way to discover the genetic bases that promote yeast adaptation to nitrogen-deficient environments are selection experiments, where a yeast population undergoes selection under conditions of nitrogen restriction for a number of generations, to then identify by sequencing the molecular characteristics that promote this adaptation. In this work, we carried out selection experiments in bioreactors imitating wine fermentation under nitrogen-limited fermentation conditions (SM60), using the heterogeneous SGRP-4X yeast population, to then sequence the transcriptome and the genome of the population at different time points of the selection process. The transcriptomic results showed an overexpression of genes from the NA strain (North American/YPS128), a wild, non-domesticated isolate. In addition, genome sequencing and allele frequency results allowed several QTLs to be mapped for adaptation to nitrogen-limited fermentation. Finally, we validated the ECM38 allele of NA strain as responsible for higher growth efficiency under nitrogen-limited conditions. Taken together, our results revealed a complex pattern of molecular signatures favouring adaptation of the yeast population to nitrogen-limited fermentations, including differential gene expression, allele frequency changes and loss of the mitochondrial genome. Finally, the results suggest that wild alleles from a non-domesticated isolate (NA) may have a relevant role in the adaptation to the assayed fermentation conditions, with the consequent potential of these alleles for the genetic improvement of wine yeast strains.

Published studies have reported significant selection with respect to the G6pd locus for Drosophila melanogaster reared on Na-octanoate food. We have reexamined the selective effects of Na-octanoate on egg to adult viability with respect to the G6pd polymorphism using specially constructed X chromosomes. Four experiments were carried out using different 6Pgd backgrounds in two recombinant sets of chromosomes segregating for the G6pd locus but constructed so as to minimize variation over most of the X chromosome. In addition, two measures of viability were used, and the size of the experiments and their associated degrees of freedom are approximately double those reported in the former studies. Our results find no evidence for differential selection on G6pd genotypes (males and females) by Na-octanoate and, therefore, do not corroborate the positive results of selection reported by other investigators. The reasons for our different results are discussed.

One approach to the study of allozyme polymorphisms in natural populations is to relate changes in the selection coefficients of different alleles at a specific enzyme locus to environmental variables. The experiments of Dejong et al. (1972) and of Dejong and Scharloo (1976) indicate that electrophoretic variants of the amylase enzyme in Drosophila melanogaster affect the fitness of individuals and that this effect is dependent on the carbohydrate source in the food. A controlled selection experiment by Hickey (1977) showed a predictable response of gene frequencies in experimental populations grown on different food media. The amylase variant which has the higher enzyme activity is at a selective disadvantage when the dietary carbohydrate source is in the form of simple sugars. However, the relative selective value of this variant is enhanced when the dietary sugars are replaced by starch. These results suggest that the amylase system may be very useful in demonstrating the action of selection at a specific enzyme locus. The following set of experiments is designed to confirm the finding of selective changes in gene frequency. Moreover, I hoped to eliminate the effects of linked loci by using several independently-derived high-activity and low-activity amylase variants, and especially by using those with different electrophoretic mobilities.

Vein patterns have been studied in lines of Drosophila melanogaster selected for increased and for reduced expression of the mutants plexus and net. Within each selection line, and in certain crosses involving these and other vein mutants and selection lines, the pattern of extra venation at all levels of mutant expression is highly specific. Measurements of the position and frequency of vein fragments allowed a series of profiles to be constructed which represent the relative tendency to form veins at various positions on the wing. The general phenotypic effects of many vein mutants as well as the overall action of selected polygenic modifiers of vein length are discussed in relation to the resulting model of subthreshold developmental potential. Correlations between this subthreshold pattern and the veins of related Diptera suggest that many of the subthreshold veins may be remnants of ancestral venation.

The woodland white-footed mouse Peromyscus leucopus noveboracensis cooccurs with the prairie deermouse P. maniculatus bairdi in old fields and prairies of southern Wisconsin. In order to examine possible mechanisms of this coexistence, fieldcaught individuals of both species were brought into the laboratory for testing. In a seed preference test in which mice were offered two species of old-field grass seeds and two species of native prairie grass seeds, all the mice preferred the old-field grass seeds. Neither species favored either habitat (field or woods) for activity during two 0.5-hr observation periods or for foraging. However, P. m. bairdi removed significantly less food from the woods habitat than did P. 1. noveboracensis and there was a significant difference in preferred nest location, with P. m. bairdi nesting primarily in the field and P. 1. noveboracensis in the woods. In 20 paired behavior trials, P. m. bairdi was dominant in two, P. 1. noveboracensis in 12, and there was mutual avoidance in six. The results suggest that interference competition may, in part, account for the distribution patterns of these species.

Young Canada geese (Branta canadensis) and blue geese (Chen caerulescens) were tested experimentally for food preferences among six speces of grasses and sedges. Fifty-cm2 sods of two plant species were presented to two goslings in a test enclosure. The time intervals that individual birds spent feeding on each sod during a 90-minute test were recorded. Two pairs of goslings of each species were tested against all pair combination of the six plants. Each species show significant preference for some plants over others, and the preferences of the two species were demonstrably different. Faults in experimental design are discussed, and it is shown that results cannot be extended directly to free-ranging wild geese. Five species of geese nest on the coastal plains and larger islands of western and northern Hudson Bay. During the brood rearing period, two or more species may frequently be observed grazing together, apparently from a common food supply. This experiment, part of a broad study of food resources and their use by nesting geese, was designed to discover if young Canada and blue geese developed preferences for a restricted range of the available plant species, and, if so, whether the preferences differed between species. In food preference studies involving seeds, it is standard procedure to present test animals weighed amounts of seeds and either to record the order of disappearance (Michael and Beckwith 1955), or the weight differences after a given period of time (McFarland and George 1966). Because both species of geese were eating aerial parts of green vegetation, neither of these approaches was deemed suitable for the present test. In order to maintain the most natural conditions, geese were presented with fresh intact plants still rooted in sod. Although the six plant species tested were all identified in the feces of free-ranging geese, the principal criterion for choosing these species was their availability in sufficient pure stands to provide sods for the experiment. Description of the test plants appears in Table 1. This study was supported by contracts from the Canadian Wildlife Service, and by grants from the National Research Council of Canada, The Wildlife Management Institute, and the Arctic Institute of North America. The generous support of all these agencies is gratefully acknowledged. We wish also to thank R. Jones, T. T. McNulty, M. Harvey, P. Prevett, and W. Baumann or their assistance during the experiments. Special thanks are due to H. Boyd who reviewed manuscript.

Various types of selection with respect to ascospore length were practised with wild-type strains of Neurospora crass(L. The effect of all types of selection over 11 generations was essentially the same. A significant increase in mean ascospore length, a tendency for a decrease in the coefficient of variation, and a decrease in fertility were observed in each case. These results are discussed and a hypothesis to explain them is put forward.

Experimental evolution can be a useful tool for testing the impact of environmental factors on adaptive changes in populations, and this approach is being increasingly used to understand the potential for evolutionary responses in populations under changing climates. However, selective factors will often be more complex in natural populations than in laboratory environments and produce different patterns of adaptive differentiation. Here we test the ability of laboratory experimental evolution under different temperature cycles to reproduce well-known patterns of clinal variation in Drosophila melanogaster. Six fluctuating thermal regimes mimicking the natural temperature conditions along the east coast of Australia were initiated. Contrary to expectations, on the basis of field patterns there was no evidence for adaptation to thermal regimes as reflected by changes in cold and heat resistance after 1-3 years of laboratory natural selection. While laboratory evolution led to changes in starvation resistance, development time, and body size, patterns were not consistent with those seen in natural populations. These findings highlight the complexity of factors affecting trait evolution in natural populations and indicate that caution is required when inferring likely evolutionary responses from the outcome of experimental evolution studies.

Although artificial-selection experiments seem well suited to testing our ability to predict evolution, the correspondence between predicted and observed responses is often ambiguous due to the lack of uncertainty estimates. We present equations for assessing prediction error in direct and indirect responses to selection that integrate uncertainty in genetic parameters used for prediction and sampling effects during selection. Using these, we analyzed a selection experiment on floral traits replicated in two taxa of the Dalechampia scandens (Euphorbiaceae) species complex for which G-matrices were obtained from a diallel breeding design. After four episodes of bidirectional selection, direct and indirect responses remained within wide prediction intervals, but appeared different from the predictions. Combined analyses with structural-equation models confirmed that responses were asymmetrical and lower than predicted in both species. We show that genetic drift is likely to be a dominant source of uncertainty in typically-dimensioned selection experiments in plants and a major obstacle to predict short-term evolutionary trajectories. This article is protected by copyright. All rights reserved.

Ce rapport est disponible dans : BioRxiv. This article has been peer-reviewed and recommended by Peer Community in Evolutionary Biology; Experiments comparing native to introduced populations or distinct introduced populations to each other show that phenotypic evolution is common and often involves a suit of interacting phenotypic traits. We define such sets of traits that evolve in concert and contribute to the success of invasive populations as an ‘invasion syndrome’. The invasive Harlequin ladybird Harmonia axyridis displays such an invasion syndrome with, for instance, females from invasive populations being larger and heavier than individuals from native populations, allocating more resources to reproduction, and spreading reproduction over a longer lifespan. Invasion syndromes could emerge due to selection acting jointly and directly on a multitude of traits, or due to selection on one or a few key traits that drive correlated indirect responses in other traits. Here, we investigated the degree to which the H. axyridis invasion syndrome would emerge in response to artificial selection on either female body mass or on age at first reproduction, two traits involved in their invasion syndrome. To further explore the interaction between environmental context and evolutionary change in molding the phenotypic response, we phenotyped the individuals from the selection experiments in two environments, one with abundant food resources and one with limited resources. The two artificial selection experiments show that the number of traits showing a correlated response depends upon the trait undergoing direct selection. Artificial selection on female body mass resulted in few correlated responses and hence poorly reproduced the invasion syndrome. In contrast, artificial selection on age at first reproduction resulted in more widespread phenotypic changes, which nevertheless corresponded only partly to the invasion syndrome. The artificial selection experiments also revealed a large impact of diet on the traits, with effects dependent on the trait considered and the selection regime. Overall, our results indicate that direct selection on multiple traits was likely necessary in the evolution of the H. axyridis invasion syndrome. Furthermore, they show the strength of using artificial selection to identify the traits that are correlated in different selective contexts, which represents a crucial first step in understanding the evolution of complex phenotypic patterns, including invasion syndromes.

Genetic correlations among behavioural traits are often controlled by pleiotropic genes. Many studies suggest the existence of genetic correlations among behavioural traits based on artificial selection experiments in the laboratory. However, few studies have examined whether behavioural correlations in the laboratory are maintained in the field, where natural selection works. Artificial selection experiments showed a behavioural correlation among death feigning, walking movement, and locomotor activity in the red flour beetle (Tribolium castaneum). This study investigated whether this behavioural correlation is observed in wildT. castaneumpopulations. We also collected beetles from various regions in Japan and investigated the geographic variation in these traits. There was geographic variation in the three behavioural traits. However, these behavioural traits were not correlated. The results suggest that the genetic correlations among behavioural traits are not maintained in the field. Therefore, the results derived from laboratory experiments may be overestimated. The same correlation between traits was not believed to arise in the field, as the indoor results may have been caused by unrealistic selection pressures. Further laboratory and field investigations are both needed.

The first records of outbreaks of the Pine Spittle bug Ocoaxo assimilis Walker were recently identified from Puebla, Mexico, which promoted more than 2600 ha of forest foliar fall. Beyond the taxonomic and distribution information of this species, the basic traits of its biology remain unknown. This study aims to describe some biological aspects of O. assimilis, in a natural pine forest at Nicol&aacute, s Bravo, Puebla (NB). Using morphological characteristics and a phylogenetic analysis of a fragment of cytochrome oxidase subunit I mtDNA (COI), immature instars with adults were studied, the instar number was determined by means of a multivariate analysis of 19 morphological characteristics of 121 specimens. The systematic sampling to evaluate the occurrence of nymphal specimens during a year, plus host selection experiments, allowed for determination of the abundance over time, voltism, and host preferences. Phylogenetic analysis of the COI supported that both nymphs and adults collected in NB correspond to O. assimilis. Principal coordinate analysis supported the existence of five nymphal stages. Field sampling and host selection experiments indicated that this species displays a single generation per year, is associated with the rainy season, and that specimens from the three first nymphal stages feed on roots of eight host species (one grass, four herbaceous species, one bush, and two trees). From the fourth instar, the insects feed on pine roots to complete their development, and when they are adults, they migrate to needles of young or mature pine stands of Pinus pseudostrobus to feed and reproduce.

A betulinic acid-based compound, bevirimat (BVM), inhibits HIV-1 maturation by blocking a late step in protease-mediated Gag processing: the cleavage of the capsid-spacer peptide 1 (CA-SP1) intermediate to mature CA. Previous studies showed that mutations conferring resistance to BVM cluster around the CA-SP1 cleavage site. Single amino acid polymorphisms in the SP1 region of Gag and the C terminus of CA reduced HIV-1 susceptibility to BVM, leading to the discontinuation of BVM’s clinical development. We recently reported a series of “second-generation” BVM analogs that display markedly improved potency and breadth of activity relative to the parent molecule. Here, we demonstrate that viral clones bearing BVM resistance mutations near the C terminus of CA are potently inhibited by second-generation BVM analogs. We performed de novo selection experiments to identify mutations that confer resistance to these novel compounds. Selection experiments with subtype B HIV-1 identified an Ala-to-Val mutation at SP1 residue 1 and a Pro-to-Ala mutation at CA residue 157 within the major homology region (MHR). In selection experiments with subtype C HIV-1, we identified mutations at CA residue 230 (CA-V230M) and SP1 residue 1 (SP1-A1V), residue 5 (SP1-S5N), and residue 10 (SP1-G10R). The positions at which resistance mutations arose are highly conserved across multiple subtypes of HIV-1. We demonstrate that the mutations confer modest to high-level maturation inhibitor resistance. In most cases, resistance was not associated with a detectable increase in the kinetics of CA-SP1 processing. These results identify mutations that confer resistance to second-generation maturation inhibitors and provide novel insights into the mechanism of resistance. IMPORTANCE HIV-1 maturation inhibitors are a class of small-molecule compounds that block a late step in the viral protease-mediated processing of the Gag polyprotein precursor, the viral protein responsible for the formation of virus particles. The first-in-class HIV-1 maturation inhibitor bevirimat was highly effective in blocking HIV-1 replication, but its activity was compromised by naturally occurring sequence polymorphisms within Gag. Recently developed bevirimat analogs, referred to as “second-generation” maturation inhibitors, overcome this issue. To understand more about how these second-generation compounds block HIV-1 maturation, here we selected for HIV-1 mutants that are resistant to these compounds. Selections were performed in the context of two different subtypes of HIV-1. We identified a small set of mutations at highly conserved positions within the capsid and spacer peptide 1 domains of Gag that confer resistance. Identification and analysis of these maturation inhibitor-resistant mutants provide insights into the mechanisms of resistance to these compounds.

To optimize diet particle size for ingestion by zebrafish larvae, Danio rerio, a series of diet selection experiments were carried out using two different length classes: 5-day-old, first feeding larvae with a mean standard length (MLs) of 3.8 mm and 15-day-old larvae with MLs of 5.2 mm. For this purpose, crosslinked protein-walled capsules with five different size classes (≤20, 21-45, 46-75, 76-106, and 107-212 μm) were used in selection experiments. A particle size selection model was then developed after accounting for both rate of loss of capsules in the water column and their ingestion by larvae. Results indicated that concentration of larger particles in the water column decreased rapidly and less than 20% of capsules larger than 75 μm were available for the larvae after 30 min. Zebrafish larvae accepted a wide range of particle sizes, but larvae preferred particles much smaller than the maximum size they could ingest. While first feeding larvae preferred 21-45 μm capsules, 15-day-old larvae preferred capsules in the 47-75 μm size range. A better understanding of the behavior of small-sized food particles in the water column and their acquisition by fish larvae is important to optimize feeding protocols in successful larvae culture.

Vertebrates exhibit extensive variation in relative brain size. It has long been assumed that this variation is the product of ecologically driven natural selection. Yet, despite more than 100 years of research, the ecological conditions that select for changes in brain size are unclear. Recent laboratory selection experiments showed that selection for larger brains is associated with increased survival in risky environments. Such results lead to the prediction that increased predation should favour increased brain size. Work on natural populations, however, foreshadows the opposite trajectory of evolution; increased predation favours increased boldness, slower learning, and may thereby select for a smaller brain. We tested the influence of predator-induced mortality on brain size evolution by quantifying brain size variation in a Trinidadian killifish, Rivulus hartii , from communities that differ in predation intensity. We observed strong genetic differences in male (but not female) brain size between fish communities; second generation laboratory-reared males from sites with predators exhibited smaller brains than Rivulus from sites in which they are the only fish present. Such trends oppose the results of recent laboratory selection experiments and are not explained by trade-offs with other components of fitness. Our results suggest that increased male brain size is favoured in less risky environments because of the fitness benefits associated with faster rates of learning and problem-solving behaviour.

Marine to freshwater colonizations constitute among the most dramatic evolutionary transitions in the history of life. This study examined evolution of ionic regulation following saline-to-freshwater transitions in an invasive species. In recent years, the copepod Eurytemora affinis has invaded freshwater habitats multiple times independently. We found parallel evolutionary shifts in ion-motive enzyme activity (V-type H + ATPase, Na + /K + -ATPase) across independent invasions and in replicate laboratory selection experiments. Freshwater populations exhibited increased V-type H+ ATPase activity in fresh water (0 PSU) and declines at higher salinity (15 PSU) relative to saline populations. This shift represented marked evolutionary increases in plasticity. In contrast, freshwater populations displayed reduced Na + /K + -ATPase activity across all salinities. Most notably, modifying salinity alone during laboratory selection experiments recapitulated the evolutionary shifts in V-type H + ATPase activity observed in nature. Maternal and embryonic acclimation could not account for the observed shifts in enzyme activity. V-type H + ATPase function has been hypothesized to be critical for freshwater and terrestrial adaptations, but evolution of this enzyme function had not been previously demonstrated in the context of habitat transitions. Moreover, the speed of these evolutionary shifts was remarkable, within a few generations in the laboratory and a few decades in the wild.

RWJ-416457 is a novel investigational oxazolidinone with minimum inhibitory concentrations (MICs) to staphylococci and enterococci that are two- to four-fold lower than those of linezolid. Single-step and serial passage in vitro resistance selection experiments were performed for RWJ-416457 and linezolid with Staphylococcus aureus and Enterococcus faecalis laboratory and clinical isolates. RWJ-416457 selected for resistant mutants in single-step selections at a frequency of ≤1×10(-10), similar to that of linezolid. In serial passage selection experiments, a G2576T transversion in the domain V region of the 23S rRNA gene was the predominant mutation observed for both oxazolidinones, suggesting similar 23S rRNA binding sites. The associated development of increasing oxazolidinone resistance in E. faecalis (four 23S rRNA alleles) required fewer passages than with S. aureus isolates (six 23S rRNA alleles), and resistance was generally proportionate to the number of mutated (G2576T) 23S rRNA alleles. Fold changes in MICs were similar for both compounds, and MICs for RWJ-416457 remained two- to four-fold lower than those of linezolid for mutants selected by either compound. Serial passage of linezolid with S. aureus OC 2878 yielded a novel A2572T 23S rRNA mutation, whilst the final passages of S. aureus OC 10517 with RWJ-416457 resulted in the apparent loss of a mutated (G2576T) allele 6.

BACKGROUND: Although cross-resistance between compounds in the same insecticide group is a frequently observed phenomenon, cross-resistance between groups that differ in structural and functional characteristics can be extremely unpredictable. In the case of controlling the whitefly, Bemisia tabaci Gennadius, neonicotinoids and the pyridine azomethine antifeedant pymetrozine represent independent lines of discovery that should be suited for alternation to avoid prolonged selection for the same resistance mechanism. Reports of an association between responses to neonicotinoids and pymetrozine were investigated by resistance profiling of seven B. tabaci strains and complementary reciprocal selection experiments. RESULTS: All strains demonstrated a consistent correlation between responses to three neonicotinoid compounds: thiamethoxam, imidacloprid and acetamiprid. Responses to neonicotinoids for six field strains clearly correlated with responses to pymetrozine. Reciprocal selection experiments confirmed an unexpected case of intergroup cross-resistance. A seventh strain exhibited a so far unique phenotype of strong resistance to pymetrozine but full susceptibility to neonicotinoids. Selection experiments confirmed that in this strain the mechanism of pymetrozine resistance is specific and has no implications for neonicotinoids. CONCLUSION: Cross-resistance between neonicotinoids and pymetrozine in B. tabaci probably reflects the overexpression of a cytochrome-P450-dependent monooxygenase capable of metabolising both types of compound in spite of their apparent structural dissimilarity. Given the predominance of this mechanism in B. tabaci, both can contribute to resistance management but should be placed within the same treatment ‘window’. Copyright © 2010 Society of Chemical Industry

A diamondback moth (DBM) colony (KOBII) originally collected from cabbage fields of Iwaoka-cho in Kobe City, Japan, where acetamiprid is the primary insecticide for DBM control was selected for studies on resistance to acetamiprid, phenthoate, esfenvalerate and cartap, using the leaf-dipping method. Resistance to acetamiprid was slow to develop in KOBII compared with the other insecticides. Three selection experiments each with phenthoate and esfenvalerate yielded a resistance ratio (RR) of 140 and 222, respectively, in the selected strains compared with a part of KOBII that was not exposed to any insecticide (KOBII-NS). Three selection experiments with cartap also gave an RR of 15. However, six selection experiments with acetamiprid yielded an RR of just 9.5 in the selected strain. When cross-resistance to acetamiprid was evaluated, the cartap-resistant strain showed a moderate level of cross-resistance to acetamiprid. In the case of the phenthoate-resistant strain, a very low cross-resistance to acetamiprid was observed. There was however no discernible cross-resistance to acetamiprid in the esfenvalerate-resistant strain.

Adults of the reddish green symbiotic crab Allopetrolisthes spinifrons obtain different degrees of camouflage from the red, green, reddish green, and blue sea anemones Phymactis clematis, and the orange Phymanthea pluvia on which they are commonly found. Previous studies have indicated that the distribution of the crab on sea anemones may be influenced by the host's coloration. During the present study, we tested whether adult crabs dwell more commonly on those sea anemones that offer a higher degree of camouflage, and whether “behavioral preferences” can explain crab distribution on sea anemone species and color morphs in the field. We examined the frequency of occurrence of adult crabs on 200 sea anemones of each color morph, and crab distribution was compared to that expected by the relative abundance of different anemone hosts in the field. Adult crabs occurred more frequently than expected by chance on sea anemones most similar to their own color (reddish green), and occurred less frequently than expected by chance on sea anemones where homochromy was reduced (e.g. blue). Multiple host selection experiments conducted under laboratory conditions demonstrated that adult crabs avoid blue sea anemones compared to other host color morphs offered for colonization, but no preference was observed among red, green, reddish green, and orange sea anemones. These results suggest that “behavioral preference” play a role in determining the field distribution of A. spinifrons adult crabs in the field. The lack of preference for reddish green sea anemones in the laboratory, but its high frequency of occupancy by adult crabs in the intertidal, further suggests that factors other than homochromy-related preferences (e.g. sea anemones habitat) might affect crab distribution in the field. Alternative host selection experiments revealed that the specific host from which crabs were collected (source host) affected the host-choice behavior of crabs, indicating that previous experience is important in choice of sea anemone hosts.

SUMMARY 1. The nutritional value of the bacterivorous ciliate Tetrahymena pyriformis and the algivorous ciliate Coleps sp., as well as the heterotrophic flagellate Chilomonas paramecium and the autotrophic flagellate Cryptomonas ovata, were investigated in population growth experiments using the rotifer B. calyciflorus. The two ciliates, both flagellates, which were of similar size, shape and mobility, were each offered as a sole diet and as a supplement to the alga Monoraphidium minutum, known to support reproduction of B. calyciflorus. 2. To further test nutritional differences between the prey organisms, prey selection experiments were conducted in which B. calyciflorus was able to select between the bacterivorous and algivorous ciliate, and between the heterotrophic and autotrophic flagellate. 3. The results demonstrated that both ciliates and the heterotrophic flagellate were not sufficient to support reproduction of B. calyciflorus when offered as a sole diet. They were, however, a good supplement to algal prey (except for the bacterivorous ciliate T. pyriformis). In the prey selection experiments, B. calyciflorus positively selected for the algivorous Coleps sp. and the autotrophic C. ovata. 4. Overall, ciliates and heterotrophic flagellates may enhance survival of B. calyciflorus, but reproduction of the rotifer is likely to rely on algal prey. Both higher population growth of B. calyciflorus when fed the algivorous Coleps and the autotrophic Cryptomonas, along with their positive selection, give evidence for prey specific differences in nutrition, with algivorous or autotrophic prey species tending to be of higher nutritional value.

Genetically-based social behaviors are subject to evolutionary change in response to natural selection. Numerous microbial systems provide not only the opportunity to understand the genetic mechanisms underlying specific social interactions, but also to observe evolutionary changes in sociality over short time periods. Here we summarize experiments in which behaviors of the social bacterium Myxococcus xanthus changed extensively during evolutionary adaptation to two relatively asocial laboratory environments. M. xanthus moves cooperatively, exhibits cooperative multicellular development upon starvation and also appears to prey cooperatively on other bacteria. Replicate populations of M. xanthus were evolved in both structured (agar plate) and unstructured (liquid) environments that contained abundant resources. The importance of social cooperation for evolutionary fitness in these habitats was limited by the absence of positive selection for starvation-induced spore production or predatory efficiency. Evolved populations showed major losses in all measured categories of social proficiency- motility, predation, fruiting ability, and sporulation. Moreover, several evolved genotypes were observed to exploit the social behavior of their ancestral parent when mixed together during the developmental process. These experiments that resulted in both socially defective and socially exploitative genotypes demonstrate the power of laboratory selection experiments for studying social evolution at the microbial level. Results from additional selection experiments that place positive selection pressure on social phenotypes can be integrated with direct study of natural populations to increase our understanding of principles that underlie the evolution of microbial social behavior.

Selection experiments with Drosophila have revealed constraints on the simultaneous evolution of life history traits. However, the responses to selection reported by different research groups have not been consistent. Two possible reasons for these inconsistencies are (i) that different groups used different environments for their experiments and (ii) that the selection environments were not identical to the assay environments in which the life history traits were measured. We tested for the effect of the assay environment in life history experiments by measuring a set of Drosophila selection lines in laboratories working on life history evolution with Drosophila in Basel, Groningen, Irvine and London. The lines measured came from selection experiments from each of these laboratories. In each assay environment, we measured fecundity, longevity, development time and body size. The results show that fecundity measurements were particularly sensitive to the assay environment. Differences between assay and selection environment in the same laboratory or differences between assay environments between laboratories could have contributed to the differences in the published results. The other traits measured were less sensitive to the assay environment. However, for all traits there were cases where the measurements in one laboratory suggested that selection had an effect on the trait, whereas in other laboratories no such conclusion would have been drawn. Moreover, we provide good evidence for local adaptation in early fecundity for lines from two laboratories.

The degu, Octodon degus (Rodentia, Octodontidae) is a diurnal herbivore inhabiting the semiarid and mediterranean environments of northern and central Chile. In the field, degus are constrained to specific foraging areas, mainly by their limited thermal tolerance and by environmental food quality. Consequently, we hypothesized that degus must balance their diet selection by maximizing nutrients/digestible energy intake, in the face of their time and digestive constraints and seasonal/spatial changes in food quality; and by minimizing thermoregulatory risk, in the face of their low evaporative water loss and seasonal/spatial changes in environmental temperatures among foraging areas. This hypothesis was tested in a series of diet selection experiments conducted in an experimental arena, as well as in nutritional trials, involving synthetic diets with different fiber content and thermal patches. As predicted, results of the arena food selection experiments, as well as the nutritional trials, demonstrated that O. degus prefers items of low-fiber composition. However, food selection is compromised by seasonal and spatial changes in food quality and environmental temperatures, coupled with feeding time and digestive and thermoregulatory constraints.

An important issue in the study of the evolution of aging in Drosophila melanogaster is whether decreased early fecundity is inextricably coupled with increased life span in selection experiments on age at reproduction. Here, this problem has been tackled using an experimental design in which selection is applied directly to longevity. Selection appeared successful for short and long life, in females as well as males. Progeny production of females selected for long life was lower than for short-lived females throughout their whole life. No increase of late-life reproduction in long-lived females occurred, as has been found in selection experiments on age at reproduction. This discrepancy is explained in terms of the inadequacy of the latter design to separate selection on life span from selection on late-life fecundity. Moreover, starvation resistance and fat content were lower for adults selected for short life. In general, the data support the negative-pleiotropy-disposable-soma theory of aging, and it is hypothesized that the pleiotropic allocation of resources to maintenance versus to reproduction as implicated in the theory might involve lipid metabolism. It is argued that further research on this suggestion is urgent and should certainly comprise observations on male reproduction because these are for the greater part still lacking. In conclusion, the longevity of D. melanogaster can be genetically altered in a direct-selection design, and such an increase is accompanied by a decreased general reproduction and thus early reproduction.

Criteria for comparing the risk of resistance development among single insecticides and between mixtures and sequences of two insecticides are described. The rate of development of resistance to an insecticide is proportional to the population’s heritability (h2) of resistance to that insecticide. When cross-resistance is absent, a sequence of two insecticides is expected to be more durable than a mixture unless the population’s h2 of resistance to the mixture is less than half of the mean of the population’s h2 of resistance to the two individual components of the mixture. We applied these criteria to II previously reported selection experiments with the biopesticide Bacillus thuringiensis and Indianmeal moth, Plodia interpunctella (Hubner), a major pest of stored grain. The risk of resistance development did not differ significantly between the HD-1 strain of B. thuringiensis ssp. kurstaki and three other strains (HD-112, HD-133, and HD-198) of B. thuringiensis . Significant declines in realized h2 of resistance during individual selection experiments suggest that the initial frequency of resistance alleles was much higher than previously assumed. Our analysis also suggests that a mixture of HD-1 + HD-133 would not slow resistance development compared with a sequence of HD-1 followed by HD-133. Rapid evolution of resistance to the mixture of HD-1 + HD-133, which contained at least six different toxins, contradicts the claim that multiple toxins prevent or greatly retard resistance development.