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Important Force (important + force)
Selected AbstractsINCREASED POSTCOPULATORY SEXUAL SELECTION REDUCES THE INTRAMALE VARIATION IN SPERM DESIGNEVOLUTION, Issue 6 2008Simone Immler Sperm competition is an important force driving the evolution of sperm design and function. Inter- and intraspecific variation in sperm design are strongly influenced by the risk of sperm competition in many taxa. In contrast, the variation among sperm of one male (intramale variation) is less well understood. We investigated intramale variation in sperm design in passerine birds and found that risk of sperm competition is negatively associated with intramale variation. This result is the first clear evidence that variation among sperm within an individual male is influenced by postcopulatory sexual selection. Our finding has important implications for male traits under pre- and postcopulatory sexual selection. [source] Nanotechnologies: Tools for sustainability in a new wave of water treatment processesINTEGRATED ENVIRONMENTAL ASSESSMENT AND MANAGEMENT, Issue 4 2006Jean-Yves Bottero Abstract In the environmental technology industry alone, nanomaterials will enable new means of reducing the production of industrial wastes, using resources more sparingly, remediating industrial contamination, providing potable water, and improving the efficiency of energy production. This paper discusses three new kinds of nanotechnology materials that should be developed in the future: Membranes, oxidants, and adsorbents. Nanoscale control of membrane architecture may yield membranes of greater selectivity and lower cost in both water treatment and water fabrication. Fullerene-based oxidant nanomaterials such as C60 have a high electron affinity and reactivity, and are capable of producing reactive oxygen species such as singlet oxygen and superoxides. Fullerenes might be used in engineered systems to photocatalytically oxidize organic contaminants, or inhibit or inactivate microbes. The ability to tailor surfaces can help to increase adsorbing capacities or recognize specific contaminants. The potential environmental risks are that nanomaterials could interact with biota and that their toxicity adversely may affect ecosystems. As nanochemistry emerges as an important force behind new environmental technologies, we are also presented with the responsibility of considering the environmental implications of an emerging technology at its inception and taking every precaution to ensure that these technologies develop as tools of sustainability rather than becoming future liabilities. [source] Humidity parameters from temperature: test of a simple methodology for European conditionsINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 7 2008Yvonne Andersson-Sköld Abstract Atmospheric water content is important for local and regional climate, and for chemical processes of soluble and solute species in the atmosphere. Further, vapour pressure deficit (D) is one of the key controls on the opening of stomata in plants and is thus an important force for evapotransporation, plant respiration and biomass production and for the uptake of harmful pollutants such as ozone through the stomata. Most meteorological stations typically measure both temperature and relative humidity (RH). However, even if recorded at finer time resolution, it is usually the daily or often monthly means of RH which are published in climate reports. Unfortunately, such data cannot be used to obtain the changes in RH or vapour pressure deficit over the day, as this depends strongly on the diurnal temperature variation during the day and not upon the mean temperature. Although RH typically changes significantly over the day, the ambient vapour pressure is often remarkably constant. Here a simple method to estimate diurnal vapour pressure is evaluated, based upon an assumed constant vapour pressure, and that recorded minimum temperatures approximate dew-point temperatures. With a knowledge of only temperature, we will show that day to day estimates of vapour pressure, humidity and especially D, can be made with reasonable accuracy. This methodology is tested using meteorological data from 32 sites covering a range of locations in Europe. Such a simple methodology may be used to extract approximate diurnal curves of vapour pressures from published meteorological data which contains only minimum temperatures for each day, or where humidity data are not available. Copyright © 2007 Royal Meteorological Society [source] Genetic caste determination in Pogonomyrmex harvester ants imposes costs during colony foundingJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 2 2006T. SCHWANDER Abstract Some populations of Pogonomyrmex harvester ants comprise genetically differentiated pairs of interbreeding lineages. Queens mate with males of their own and of the alternate lineage and produce pure-lineage offspring which develop into queens and inter-lineage offspring which develop into workers. Here we tested whether such genetic caste determination is associated with costs in terms of the ability to optimally allocate resources to the production of queens and workers. During the stage of colony founding, when only workers are produced, queens laid a high proportion of pure-lineage eggs but the large majority of these eggs failed to develop. As a consequence, the number of offspring produced by incipient colonies decreased linearly with the proportion of pure-lineage eggs laid by queens. Moreover, queens of the lineage most commonly represented in a given mating flight produced more pure-lineage eggs, in line with the view that they mate randomly with the two types of males and indiscriminately use their sperm. Altogether these results predict frequency-dependent selection on pairs of lineages because queens of the more common lineage will produce more pure-lineage eggs and their colonies be less successful during the stage of colony founding, which may be an important force maintaining the coexistence of pairs of lineages within populations. [source] Temporal variability of disturbances: is this important for diversity and structure of marine fouling assemblages?MARINE ECOLOGY, Issue 3 2007Heather Sugden Abstract Natural communities are constantly changing due to a variety of interacting external processes and the temporal occurrence and intensity of these processes can have important implications for the diversity and structure of marine sessile assemblages. In this study, we investigated the effects of temporal variation in a disturbance regime, as well as the specific timing of events within different regimes, on the composition and diversity of marine subtidal fouling assemblages. We did this in a multi-factorial experiment using artificial settlement tiles deployed at two sites on the North East coast of England. We found that although there were significant effects of disturbances on the composition of assemblages, there were no effects of either the variation in the disturbance regime or the specific timing of events on the diversity or assemblage composition at either site. In contrast to recent implications we conclude that in marine fouling assemblages, the variability in disturbance regimes (as a driving force) is unimportant, while disturbance itself is an important force for structuring robust ecosystems. [source] Intraspecific variation and population structure of the German cockroach, Blattella germanica, revealed with RFLP analysis of the non-transcribed spacer region of ribosomal DNAMEDICAL AND VETERINARY ENTOMOLOGY, Issue 2 2007D. V. MUKHA Abstract Little information is available on genetic variation within and between populations of pest cockroaches. In this study, intraspecific HindIII polymorphism was investigated in the German cockroach, Blattella germanica (Linnaeus) (Dictyoptera, Blattaria: Blattellidae), using restriction fragment length polymorphisms (RFLP) of the non-transcribed spacer (NTS) region of ribosomal DNA (rDNA). Individual male insects were collected from infestations at three different pig farms. Each population was characterized by HindIII restriction fragment frequencies and haplotype (a particular X-chromosome pattern) frequencies. The inheritance of the X-chromosome HindIII rDNA patterns over 12 generations (3 years) follows Mendelian patterns, and the stability of this polymorphic marker indicates infrequent genetic recombination of variable sites. Although pairwise genetic distance measures were uncorrelated with geographical distance, the pattern of genetic differentiation of the three cockroach populations suggests that human-mediated transport of cockroaches is an important force in shaping the population genetic structure of cockroach infestations, at least at the regional scale of 10,100 km. Sequence variation in the ribosomal NTS is a useful marker, and RFLP of rDNA is a simple, robust and reproducible technique for differentiating recently diverged cockroach populations. [source] Does natural selection promote population divergence?MOLECULAR ECOLOGY, Issue 12 2002A comparative analysis of population structure using amplified fragment length polymorphism markers, quantitative traits Abstract Divergent natural selection is considered an important force in plant evolution leading to phenotypic differentiation between populations exploiting different environments. Extending an earlier greenhouse study of population differentiation in the selfing annual plant Senecio vulgaris, we estimated the degree of population divergence in several quantitative traits related to growth and life history and compared these estimates with those based on presumably neutral molecular markers (amplified fragment length polymorphisms; AFLPs). This approach allowed us to disentangle the effects of divergent selection from that of other evolutionary forces (e.g. genetic drift). Five populations were examined from each of two habitat types (ruderal and agricultural habitats). We found a high proportion of total genetic variance to be among populations, both for AFLP markers (,ST = 0.49) and for quantitative traits (range of QST: 0.26,0.77). There was a strong correlation between molecular and quantitative genetic differentiation between pairs of populations (Mantel's r = 0.59). However, estimates of population differentiation in several quantitative traits exceeded the neutral expectation (estimated from AFLP data), suggesting that divergent selection contributed to phenotypic differentiation, especially between populations from ruderal and agricultural habitats. Estimates of within-population variation in AFLP markers and quantitative genetic were poorly correlated, indicating that molecular marker data may be of limited value to predict the evolutionary potential of populations of S. vulgaris. [source] Youth organizing: From youth development to school reformNEW DIRECTIONS FOR YOUTH DEVELOPMENT, Issue 117 2008Mark R. Warren Over the past twenty years, youth organizing has grown across the country. Through organizing, young people identify issues of concern and mobilize their peers to build action campaigns to achieve their objectives. Youth organizing has been appreciated for its contributions to youth and community development. The authors use two case studies to trace the more recent emergence of youth organizing as an important force for school reform. The Boston-based Hyde Square Task Force began with a focus on afterschool programming, but its youth leaders now organize to get Boston Public Schools to adopt a curriculum addressing sexual harassment. Meanwhile, the Baltimore Algebra Project began as a peer-to-peer tutoring program but now also organizes to demand greater funding for Baltimore schools. These cases illustrate a broader phenomenon where students reverse the deficit paradigm by acting out of their own self-interest to become agents of institutional change. [source] THE U.S. WESTWARD EXPANSION,INTERNATIONAL ECONOMIC REVIEW, Issue 1 2008Guillaume Vandenbroucke The U.S. economic development in the 19th century was characterized by the westward movement of population and the accumulation of productive land in the West. This article presents a model of migration and land improvement to identify the quantitatively important forces driving these phenomena. The conclusion is that the decrease in transportation costs induced the westward migration, whereas population growth was responsible for the investment in productive land. [source] Judicial Performance and the Rule of Law in the Mexican StatesLATIN AMERICAN POLITICS AND SOCIETY, Issue 3 2006Caroline C. Beer ABSTRACT What determines how judicial institutions perform? Prominent theoretical approaches, such as international political economy, institutional rational choice, social capital, and structural theories, suggest that international economic actors, political competition, political participation, and poverty may all be important forces driving institutional behavior. This study analyzes these various theoretical approaches and uses qualitative and statistical analysis to compare judicial performance in the Mexican states. It provides evidence to support the institutional rational choice hypothesis that political competition generates judicial independence. Poverty, political participation, and an export-oriented economy seem to influence judicial access and effectiveness. [source] | ||||||||||