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Selected AbstractsMicroevolution in agricultural environments: how a traditional Amerindian farming practice favours heterozygosity in cassava (Manihot esculenta Crantz, Euphorbiaceae)ECOLOGY LETTERS, Issue 2 2005Benoît Pujol Abstract We demonstrate a novel case of selection for heterozygosity in nature, involving inadvertent human selection on a population of domesticated plants. Amerindian farmers propagate cassava (Manihot esculenta) clonally by cuttings. Seedlings also appear spontaneously in fields, and farmers allow them to grow, later using some for cuttings. These ,volunteers' contribute new genotypes. However, many are inbred, whereas multiplied clones are highly heterozygous. We demonstrate the selective retention of heterozygous volunteers. When farmers weeded fields, they killed small volunteers, but retained large ones. Plant size and heterozygosity were correlated, and both increased after weeding. The process we document allows maintenance of genotypically diverse and heterozygous clonal stocks. Demonstrating heterosis in nature usually requires large sample sizes, but novel features of our system allowed escape of this constraint. Traditional agroecosystems offer unusual opportunities for the microevolutionary studies required to give on-farm conservation of genetic resources a solid scientific basis. [source] Timeliness and effectiveness in the surgical management of persistent post-treatment periapical pathosisENDODONTIC TOPICS, Issue 1 2005MIN-KAI WU Common problems that cause persistent post-treatment periapical pathosis include infection remaining in the apical inaccessible areas, extraradicular infection including apically extruded dentine debris with bacteria present in dentinal tubules, radicular true cysts, foreign body reactions, inadequate non-surgical root canal treatment with or without iatrogenically altered root canal morphology, and vertical root fractures. Inadequate root canal treatment may be corrected non-surgically, while more complex problems may require surgical intervention. The important factors that warrant a successful surgery include good quality of the orthograde root canal treatment, deep retrograde preparation of the apical canal, and carefully cleaning and filling of the exposed isthmuses and accessory canals. Ideally, apical surgery and orthograde retreatment are performed simultaneously. In a recent study, 97% of the lesions including large ones of >10 mm in diameter healed completely within 1 year after surgical intervention. Of the teeth that showed ,complete healing' at 4 years more than 85% already ,completely healed' at 2 years; thus, the endodontic post-treatment disease might be treated surgically or non-surgically within 2 years after the previous treatment. [source] Short-run Returns around the Trades of Corporate Insiders on the London Stock ExchangeEUROPEAN FINANCIAL MANAGEMENT, Issue 1 2002Sylvain Friederich Previous work examined the long-run profitability of strategies mimicking the trades company directors in the shares of their own company, as a way of testing for market efficiency. The current paper examines patterns in abnormal returns in the days around these trades on the London Stock Exchange. We find movements in returns that are consistent with directors engaging in short-term market timing. We also report that some types of trades have superior predictive content over future returns. In particular, medium-sized trades are more informative for short-term returns than large ones, consistent with Barclay and Warner's (1993) ,stealth trading' hypothesis whereby informed traders avoid trading in blocks. Another contribution of this study is to properly adjust the abnormal return estimates for microstructure (spread) transactions costs using daily bid-ask spread data. On a net basis, we find that abnormal returns all but disappear. [source] Presynaptic source of quantal size variability at GABAergic synapses in rat hippocampal neurons in cultureEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2004Andrea Barberis Abstract The variability of quantal size depends on both presynaptic (profile of the neurotransmitter concentration in the cleft) and postsynaptic (number and gating properties of postsynaptic receptors) factors. Here we have examined the possibility that at nonsaturated synapses in cultured hippocampal neurons, changes in both the transmitter concentration peak and its clearance from the synaptic cleft may influence the variability of spontaneous miniature synaptic GABAergic currents (mIPSCs). We found that, in contrast to the slow-off GABAA receptor antagonist bicuculline, fast-off competitive antagonists such as SR-95103 and TPMPA differentially blocked small and large mIPSCs. In the presence of flurazepam, a drug believed to increase the affinity of GABA for GABAAR, small mIPSCs were enhanced more efficiently than large events. Moreover, the addition of dextran, which increases the viscosity of the extracellular fluid, preferentially increased small mIPSCs with respect to large ones. These observations suggest that changes in the concentration peak and the speed of GABA clearance in the cleft may be an important source of synaptic variability. The study of the correlation between peak amplitude and kinetics of mIPSCs allowed determination of the relative contribution of transmitter peak concentration vs. time of GABA clearance. Small synaptic responses were associated with fast onset and decay kinetics while large amplitude currents were asociated with slow kinetics, indicating a crucial role for GABA synaptic clearance in variability of mIPSCs. By using model simulations we were able to estimate the range of variability of both the concentration and the speed of clearance of the GABA transient in the synaptic cleft. [source] Linkage disequilibrium estimates of contemporary Ne using highly variable genetic markers: a largely untapped resource for applied conservation and evolutionEVOLUTIONARY APPLICATIONS (ELECTRONIC), Issue 3 2010Robin S. Waples Abstract Genetic methods are routinely used to estimate contemporary effective population size (Ne) in natural populations, but the vast majority of applications have used only the temporal (two-sample) method. We use simulated data to evaluate how highly polymorphic molecular markers affect precision and bias in the single-sample method based on linkage disequilibrium (LD). Results of this study are as follows: (1) Low-frequency alleles upwardly bias , but a simple rule can reduce bias to In the Cockpit of the FlyGERMAN RESEARCH, Issue 1 2003Martin Egelhaaf Prof. Dr. Small brains can completely outclass large ones in their performance. Thus the fly has proved to be an outstanding model system for image processing in the brain [source] Algorithms for the circular two-dimensional open dimension problemINTERNATIONAL TRANSACTIONS IN OPERATIONAL RESEARCH, Issue 6 2008Hakim Akeb Abstract In this paper, we propose three heuristics for the circular two-dimensional open dimension problem, also known as the circular strip cutting/packing problem. We first propose an open strip generation solution procedure that uses the best local position rule into the open strip. Second, we propose a simple augmented version of the first heuristic by introducing an exchange-order strategy. Third, we propose a hybrid heuristic that combines beam search and a series of target values belonging to a predetermined interval search. We evaluate the performance of these heuristics on several instances varying from small to large ones. Encouraging results have been obtained. [source] Assessing Profitability Factors in the Greek Banking System: A Multicriteria MethodologyINTERNATIONAL TRANSACTIONS IN OPERATIONAL RESEARCH, Issue 5 2002Ch. Spathis The increasing competition in the national and international banking markets, the changeover towards monetary union and the new technological innovations herald major changes in the banking environment, and challenge all banks to make timely preparations in order to enter into the new competitive monetary and financial environment. Therefore, it is interesting to investigate the effectiveness of Greek banks, as it is valued by the financial markets, i.e. the greater the efficacy the higher the competitiveness and vice versa. Taking into consideration the bank assets, we distinguish banks into small and large ones. Finding factors that make the differences in such effectiveness may explain the effective advantage of these two types of financial institutions and help us understand the ,financial intermediation' industry in Greece better. Based on their size, a classification of Greek banks, in a multivariate environment, according to the return and operation factors for the years 1990,1999 takes place. In order to investigate the differences of profitability and efficiency between small and large Greek banks, as well as the factors of profitability and operation related with the size of banks, a multicriteria methodology has been used. The results of this paper may help us determine the key success (or failure) factors of these two categories of Greek banks as well as the responsible banking decision,makers for future readjustments. [source] Behavioural responses to habitat patch boundaries restrict dispersal and generate emigration,patch area relationships in fragmented landscapesJOURNAL OF ANIMAL ECOLOGY, Issue 4 2003Nicolas Schtickzelle Summary 1We studied the consequences of behaviour at habitat patch boundaries on dispersal for the bog fritillary butterfly Proclossiana eunomia Esper in two networks of habitat differing in fragmentation and matrix quality. We tested for differences in responses to patch boundaries according to the fragmentation level of the network by analysing movement paths of adult butterflies. 2Butterflies systematically engaged in U-turns when they reached a boundary in the fragmented network while they crossed over boundaries in more than 40% of boundary encounters in the continuous one. 3We applied the Virtual Migration model (Hanski, Alho & Moilanen 2000) to capture,mark,recapture data collected in both networks. The model indicated (i) a lower dispersal rate and (ii) a lower survival during dispersal in the fragmented network. This latter difference is likely to be the key biological process leading to behavioural avoidance of patch boundary crossings. 4On the basis of this behavioural difference, we designed an individual-based simulation model to explore the relationship between patch area, boundary permeability and emigration rate. 5Predictions of the model fitted observed results of the effect of patch area on emigration rate according to fragmentation: butterflies are more likely to leave small patches than large ones in fragmented landscapes (where patch boundary permeability is low), while this relationship disappears in more continuous landscapes (where patch boundary permeability is high). [source] Influence of prey size on predation success by Zelus longipes L. (Het., Reduviidae)JOURNAL OF APPLIED ENTOMOLOGY, Issue 2-3 2002R. Cogni The effects of prey size on the predatory responses of the reduviid Zelus longipes were studied through laboratory tests using larvae of the noctuid moth Spodoptera frugiperda as preys. In tests with one caterpillar, larvae of three different weight classes were offered individually to the predator. The prey weight was positively correlated with relative weight gain by the predator, mean feeding time and discarded biomass, but not with the relative extraction rate (defined as the relative weight gain by the predator by feeding time). The different sizes of caterpillars were attacked with the same frequency, but the successful attacks were more frequent in small larvae. The median mass of successfully attacked larvae was also less than that of unsuccessfully attacked. In tests with three caterpillars, larvae of three weight classes were offered at the same time; small caterpillars were more often attacked and killed than the medium and large ones. The results showed that even if larger preys resulted in more energy intake, when the choice is possible, smaller caterpillars were more likely to be attacked than medium and large. This is probably related to the fact that successful attacks were more frequent in small larvae, and also reduced the risk of injury to the predator. [source] The effect of the extent of the study region on GIS models of species geographic distributions and estimates of niche evolution: preliminary tests with montane rodents (genus Nephelomys) in VenezuelaJOURNAL OF BIOGEOGRAPHY, Issue 7 2010Robert P. Anderson Abstract Aim, Various techniques model a species' niche and potential distribution by comparing the environmental conditions of occurrence localities with those of the overall study region (via a background or pseudoabsence sample). Here, we examine how changes in the extent of the study region (ignored or under-appreciated in most studies) affect models of two rodents, Nephelomys caracolus and Nephelomys meridensis. Location, North-central South America. Methods, We used Maxent to model the species' potential distributions via two methods of defining the study region. In Method 1 (typical of most studies to date), we calibrated the model in a large study region that included the ranges of both species. In Method 2, we calibrated the model using a smaller study region surrounding the localities of the focal species, and then applied it to the larger region. Because the study region of Method 1 is likely to include areas of suitable conditions that are unoccupied because of dispersal limitations and/or biotic interactions, this approach is prone to overfitting to conditions found near the occupied localities. In contrast, Method 2 should avoid such problems but may require further assumptions (,clamping' in Maxent) to make predictions for areas with environmental conditions beyond those found in the smaller study region. For each method, we calculated several measures of geographic interpredictivity between predictions for the species (cross-species AUC, cross-species omission rate, and proportional geographic overlap). Results, Compared with Method 1, Method 2 revealed a larger predicted area for each species, less concentrated around known localities (especially for N. caracolus). It also led to higher cross-species AUC values, lower cross-species omission rates and higher proportions of geographic overlap. Clamping was minimal and occurred primarily in regions unlikely to be suitable. Main conclusions, Method 2 led to more realistic predictions and higher estimates of niche conservatism. Conclusions reached by many studies depend on the selection of an appropriate study region. Although detailed information regarding dispersal limitations and/or biotic interactions will typically be difficult to obtain, consideration of coarse distributional patterns, topography and vegetational zones often should permit delimitation of a much more reasonable study region than the extremely large ones currently in common use. [source] Possible involvement of protein kinase C in the induction of adipose differentiation-related protein by Sterol ester in RAW 264.7 macrophagesJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 2 2001Jin-Shan Chen Abstract The accumulation of lipid droplets in macrophages contributes to the formation of foam cells, an early event in atherosclerosis. It is, therefore, important to elucidate the mechanisms by which lipid droplets accumulate and are utilized. Sterol ester (SE)-laden RAW 264.7 macrophages accumulated lipid droplets in a time-dependent manner up to 16 h, which was enhanced by cotreatment with 0.1 ,M phorbol 12-myristate 13-acetate (PMA). Inhibition of protein kinase C (PKC) activity by cotreatment with 0.3 ,M calphostin C CAL for 16 h resulted in coalescence of small lipid droplets into large ones and increased accumulation of lipid droplets, although to a lesser extent than after PMA cotreatment. Immunostaining for adipose differentiation-related protein (ADRP) revealed a fluorescent rim at the surface of each medium to large lipid droplet. ADRP appearance correlated with lipid droplet accumulation and was regulated by PMA in a time-dependent manner. Induction of ADRP expression by PMA or CAL required SE, since ADRP levels in PMA- or CAL-treated non-SE-laden macrophages were comparable to those in untreated cells. Removal of SE from the incubation medium resulted in the concomitant dissolution of lipid droplets and down-regulation of ADRP. In conclusion, the above results suggest that ADRP may be an important protein in the regulation of lipid droplet metabolism in lipid-laden macrophages and that this regulation may be mediated by PKC activity. J. Cell. Biochem. 83: 187,199, 2001. © 2001 Wiley-Liss, Inc. [source] Regional patch dynamics of Cirsium arvense and possible implications for plant-animal interactionsJOURNAL OF VEGETATION SCIENCE, Issue 2 2003S. Eber Abstract. Plant population biology considers the dynamics of plant modules within stands. However, stands themselves may have considerable regional turnover in space and time. These changes in the number, distribution and size of plant stands generate a dynamic spatial pattern with important implications for the spatial and temporal dynamics of phytophagous insects using these plants as a host. During five successive years we studied the regional distribution and patch dynamics of the creeping thistle Cirsium arvense and the distribution of associated populations of the herbivore Urophora cardui (Diptera: Tephritidae), a specialist stem gall former. The study conducted was in a 15 km2 heterogeneous, agricultural area in northeastern Bavaria. The distribution of the number of plants per patch was skewed with many more small C. arvense patches than large ones. During the five years of study, there was a 50% increase in the number of C. arvense patches, and a decrease in the mean number of plants per patch (= patch size) to less than half the patch size of the first year. Whilst patch size was randomly distributed in space, patch density showed a consistent, non-random spatial pattern. Patch density was spatially auto-correlated, with areas of high or low patch density having a characteristic dimension of ca. 1 km. Patch size was predictable in time and appeared to be regulated by size dependent processes, with the extinction probability of a patch being negatively correlated with its size. Correlated with the decline of C. arvense patch size during the study, the occupancy and total numbers of the herbivore U. cardui had a marked decrease, suggesting that the regional distribution of the stem gall former is not only influenced by patch number but more importantly by the mean patch size. With decreasing patch sizes, U. cardui was faced with an increasingly dynamic landscape due to higher extinction rates of small patches, although the mean distance between host plant patches decreased. [source] Factors influencing food collection behaviour of Brants' whistling rat (Parotomys brantsii): a central place foragerJOURNAL OF ZOOLOGY, Issue 1 2001T. P. Jackson Abstract The hypothesis that Brants' whistling rat Parotomys brantsii is a central place forager, whose foraging decisions are modified by (a) predation risk, (b) time of day, and (c) food choice, was tested. Field observations showed that whistling rats followed central place foraging rules for a single-prey loader and much of their food material was brought back to burrow entrances to feed on, with larger food items being carried back greater distances than small ones. Small food items were consumed in situ more often than large ones, suggesting that predation risk may also play a role in their foraging behaviour. Larger food items were preferentially stored at burrow entrances or carried underground, whilst smaller items tended to be consumed immediately. Individuals foraged more actively in the afternoon than in the morning and, although there was no tendency for individuals to eat more food at this time, far more food was stored or taken underground during the afternoon. Different foraging strategies were used for different plant species with some species preferentially eaten, and others stored or taken below ground more frequently. This study shows that the foraging behaviour of Brants' whistling rats is complex, and whilst they may follow simple central place foraging strategies, other factors such as the time of day and food plant species also influence their foraging behaviour. [source] atetra, a new software program to analyse tetraploid microsatellite data: comparison with tetra and tetrasatMOLECULAR ECOLOGY RESOURCES, Issue 2 2010K. VAN PUYVELDE Abstract Despite the importance of tetraploid species, most population genetic studies deal with diploid ones because of difficulties in analysing codominant microsatellite data in tetraploid species. We developed a new software program,atetra,which combines both the rigorous method of enumeration for small data sets and Monte Carlo simulations for large ones. We discuss the added value of atetra by comparing its precision, stability and calculation time for different population sizes with those obtained from previous software programs tetrasat and tetra. The influence of the number of simulations on the calculation stability is also investigated. atetra and tetrasat proved to be more precise when compared with tetra, which, however, remains faster. atetra has the same precision than tetrasat, but is much faster, can handle an infinite number of partial heterozygotes and calculates more genetic variables. The more user-friendly interface of atetra reduces possible mistakes. [source] Ice recrystallization inhibition proteins (IRIPs) and freeze tolerance in the cryophilic Antarctic hair grass Deschampsia antarctica E. Desv.PLANT CELL & ENVIRONMENT, Issue 4 2009ULRIK P. JOHN ABSTRACT Antarctic hair grass (Deschampsia antarctica E. Desv.), the only grass indigenous to Antarctica, has well-developed freezing tolerance, strongly induced by cold acclimation. Here, we show that in response to low temperatures, D. antarctica expresses potent recrystallization inhibition (RI) activity that, inhibits the growth of small ice crystals into potentially damaging large ones, is proteinaceous and localized to the apoplasm. A gene family from D. antarctica encoding putative homologs of an ice recrystallization inhibition protein (IRIP) has been isolated and characterized. IRIPs are apoplastically targeted proteins with two potential ice-binding motifs: 1,9 leucine-rich repeats (LRRs) and c. 16 ,IRIP' repeats. IRIP genes appear to be confined to the grass subfamily Pooideae and their products, exhibit sequence similarity to phytosulphokine receptors and are predicted to adopt conformations with two ice-binding surfaces. D. antarctica IRIP (DaIRIP) transcript levels are greatly enhanced in leaf tissue following cold acclimation. Transgenic Arabidopsis thaliana expressing a DaIRIP has novel RI activity, and purified DaIRIP, when added back to extracts of leaves from non-acclimated D. antarctica, can reconstitute the activity found in acclimated plants. We propose that IRIP-mediated RI activity may contribute to the cryotolerance of D. antarctica, and thus to its unique ability to have colonized Antarctica. [source] Book/market fluctuations, trading activity, and the cross-section of expected stock returnsREVIEW OF BEHAVIORAL FINANCE (ELECTRONIC), Issue 1-2 2009Amber Anand Abstract We analyze trading activity accompanying equities' switches from "growth" (low book-to-market ratios (BMRs)) to "value" (high BMRs), and vice versa. We find that a large BMR increase, that is a shift from growth to value, is accompanied by a strongly negative small order imbalance (OIB). Large OIB exhibits weaker patterns across stocks that experience large changes in book/market. The evidence indicates that growth-to-value shifts are more strongly related to small traders than large ones. The interaction of BMRs with order flows plays a crucial role in return predictability. Specifically, the predictive ability of BMRs for future returns is significantly enhanced for those stocks that have experienced book/market increases as well as high levels of net selling by way of small orders. Copyright © 2009 John Wiley & Sons, Ltd. [source] Small Things Remembered: Origins of Early Microlithic Industries in Sub-Saharan AfricaARCHEOLOGICAL PAPERS OF THE AMERICAN ANTHROPOLOGICAL ASSOCIATION, Issue 1 2002Stanley H. Ambrose Backed microliths made on small flakes and blades are considered the hallmark of Later Stone Age (LSA) industries of sub-Saharan Africa. However, some early LSA microlithic industries lack backed tools, others have extremely large ones, and some Middle Stone Age (MSA) industries also have high frequencies of blades and large backed "microliths." The invention of blades, backed microliths, and microlithization were thus separate phenomena in sub-Saharan Africa. Given this diversity and complexity, a "one size fits all" model may neither satisfactorily characterize nor explain the origin of blade-based technologies, large backed tools in the MSA, and microlithic industries in the LSA. This chapter will briefly summarize the evidence for early backed tool and microlithic industries and then evaluate several hypotheses for microlithization and backed tool production, including the invention of composite hafted tools, punch blade technology, hunting with bow and arrow in closed habitats, invention of poisons for projectiles, increased access to fine-grained raw materials, increased mobility, conservation of scarce materials, giving gifts of backed microliths made on fine-grained exotic raw materials, and manufacture of more effective specialized toolkits when increased information sharing permitted reliable anticipation of tasks. If microlithic and backed blade,based industries were invented in Africa, then understanding their origin may provide insight into the evolution of modern human behavior and the dispersal of modern humans and modern human technology out of Africa. [source] Measuring temporal variation in reproductive output reveals optimal resource allocation to reproduction in the northern grass lizard, Takydromus septentrionalisBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2007XIANG JI We measured the reproductive output of Takydromus septentrionalis collected over 5 years between 1997 and 2005 to test the hypothesis that reproductive females should allocate an optimal fraction of accessible resources in a particular clutch and to individual eggs. Females laid 1,7 clutches per breeding season, with large females producing more, as well as larger clutches, than did small females. Clutch size, clutch mass, annual fecundity, and annual reproductive output were all positively related to female size (snout,vent length). Females switched from producing more, but smaller eggs in the first clutch to fewer, but larger eggs in the subsequent clutches. The mass-specific clutch mass was greater in the first clutch than in the subsequent clutches, but it did not differ among the subsequent clutches. Post-oviposition body mass, clutch size, and egg size showed differing degrees of annual variation, but clutch mass of either the first or the second clutch remained unchanged across the sampling years. The regression line describing the size,number trade-off was higher in the subsequent clutch than in the first clutch, but neither the line for first clutch, nor the line for the second clutch varied among years. Reproduction retarded growth more markedly in small females than in large ones. Our data show that: (1) trade-offs between size and number of eggs and between reproduction and growth (and thus, future reproduction) are evident in T. septentrionalis; (2) females allocate an optimal fraction of accessible resources in current reproduction and to individual eggs; and (3) seasonal shifts in reproductive output and egg size are determined ultimately by natural selection. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 91, 315,324. [source]
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