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Particular Trait (particular + trait)
Selected AbstractsHOW REPEATABLE IS ADAPTIVE EVOLUTION?EVOLUTION, Issue 8 2008THE ROLE OF GEOGRAPHICAL ORIGIN AND FOUNDER EFFECTS IN LABORATORY ADAPTATION The importance of contingency versus predictability in evolution has been a long-standing issue, particularly the interaction between genetic background, founder effects, and selection. Here we address experimentally the effects of genetic background and founder events on the repeatability of laboratory adaptation in Drosophila subobscura populations for several functional traits. We found disparate starting points for adaptation among laboratory populations derived from independently sampled wild populations for all traits. With respect to the subsequent evolutionary rate during laboratory adaptation, starvation resistance varied considerably among foundations such that the outcome of laboratory evolution is rather unpredictable for this particular trait, even in direction. In contrast, the laboratory evolution of traits closely related to fitness was less contingent on the circumstances of foundation. These findings suggest that the initial laboratory evolution of weakly selected characters may be unpredictable, even when the key adaptations under evolutionary domestication are predictable with respect to their trajectories. [source] Winter cover crops for local ecosystems: linking plant traits and ecosystem functionJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 4 2008Brook J Wilke Abstract Winter cover crops are capable of supplying multiple economic and environmental benefits in temperate environments of North America, but the lack of adapted populations for specific environmental and agricultural contexts has resulted in cover crops that are unreliable and perform ecosystem functions unevenly. To maximize the benefits provided by winter cover crops, we argue for trait selection by crop scientists that is cognizant of desired ecosystem functions, with the goal of providing commercially available populations that have variable functions. We illustrate this approach through a case study of a promising winter annual legume cover crop, hairy vetch (Vicia villosa). Six key traits and associated functions are considered within specific agroecological contexts. We discuss tradeoffs that may occur among desired plant traits and illustrate how over-selection for a particular trait could negatively affect performance and overall benefits from a cover crop. Intraspecific combinations of complementary cover crops are suggested as means to achieve multiple agroecosystem functions. Copyright © 2008 Society of Chemical Industry [source] Architectural and growth traits differ in effects on performance of clonal plants: an analysis using a field-parameterized simulation modelOIKOS, Issue 5 2007Radka Wildová Individual traits are often assumed to be linked in a straightforward manner to plant performance and processes such as population growth, competition and community dynamics. However, because no trait functions in isolation in an organism, the effect of any one trait is likely to be at least somewhat contingent on other trait values. Thus, to the extent that the suite of trait values differs among species, the magnitude and even direction of correlation between values of any particular trait and performance is likely to differ among species. Working with a group of clonal plant species, we assessed the degree of this contingency and therefore the extent to which the assumption of simple and general linkages between traits and performance is valid. To do this, we parameterized a highly calibrated, spatially explicit, individual-based model of clonal plant population dynamics and then manipulated one trait at a time in the context of realistic values of other traits for each species. The model includes traits describing growth, resource allocation, response to competition, as well as architectural traits that determine spatial spread. The model was parameterized from a short-term (3 month) experiment and then validated with a separate, longer term (two year) experiment for six clonal wetland sedges, Carex lasiocarpa, Carex sterilis, Carex stricta, Cladium mariscoides, Scirpus acutus and Scirpus americanus. These plants all co-occur in fens in southeastern Michigan and represent a spectrum of clonal growth forms from strong clumpers to runners with long rhizomes. Varying growth, allocation and competition traits produced the largest and most uniform responses in population growth among species, while variation in architectural traits produced responses that were smaller and more variable among species. This is likely due to the fact that growth and competition traits directly affect mean ramet size and number of ramets, which are direct components of population biomass. In contrast, architectural and allocation traits determine spatial distribution of biomass; in the long run, this also affects population size, but its net effect is more likely to be mediated by other traits. Such differences in how traits affect plant performance are likely to have implications for interspecific interactions and community structure, as well as on the interpretation and usefulness of single trait optimality models. [source] Rapid changes in clonal lines: the death of a ,sacred cow'BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2003HUGH D. LOXDALE It is well established that asexually reproducing viruses and prokaryotes mutate rapidly. In contrast, the eukaryotic clone is often still treated as if it is genetically homogeneous within and between populations, i.e. that it is assumed to show genetic fidelity. However, such fidelity has rarely been tested empirically using the range of high-resolution molecular markers now available, culminating with direct sequencing of the DNA. If such a biological entity as a ,clone' really did exist, it would be a fantastic entity, differing from everything else known in biology, i.e. it would possess a population mean but no variance for any particular trait. It would not be amenable to selection and adaptive variation and would thus be unchanging in time and space. In this paper, we argue that the general acceptance of clonal fidelity is a scientific convenience, since the rate of asexual reproduction of eukaryotes is not as fast as that of bacteria and hence it is easier to accept fidelity as a ,fact' rather than test for it. We propose that part of the acceptance of fidelity may have a cultural basis and thereby is a kind of ,pre-Darwinian relic'. Instead, a clonal genotype is perhaps largely a function of marker resolution, i.e. dependent on the number and type of markers employed. If this is so and were enough of the genome explored, perhaps each individual within a clone would be found to differ genetically at particular regions of the chromosomes. The question of what constitutes a clone is not just a semantic one and impacts directly on recent attempts to understand and produce ,artificial' clones, especially of mammals. New research is already confirming that mutations and epigenetic influences play a crucial role in the success of cloning attempts. © 2003 The Linnean Society of London. Biological Journal of the Linnean Society, 2003, 79, 3,16. [source] Individual versus social complexity, with particular reference to ant coloniesBIOLOGICAL REVIEWS, Issue 2 2001CARL ANDERSON ABSTRACT Insect societies , colonies of ants, bees, wasps and termites , vary enormously in their social complexity. Social complexity is a broadly used term that encompasses many individual and colony-level traits and characteristics such as colony size, polymorphism and foraging strategy. A number of earlier studies have considered the relationships among various correlates of social complexity in insect societies; in this review, we build upon those studies by proposing additional correlates and show how all correlates can be integrated in a common explanatory framework. The various correlates are divided among four broad categories (sections). Under ,polyphenism' we consider the differences among individuals, in particular focusing upon ,caste' and specialization of individuals. This is followed by a section on ,totipotency' in which we consider the autonomy and subjugation of individuals. Under this heading we consider various aspects such as intracolony conflict, worker reproductive potential and physiological or morphological restrictions which limit individuals' capacities to perform a range of tasks or functions. A section entitled ,organization of work' considers a variety of aspects, e.g. the ability to tackle group, team or partitioned tasks, foraging strategies and colony reliability and efficiency. A final section,,communication and functional integration', considers how individual activity is coordinated to produce an integrated and adaptive colony. Within each section we use illustrative examples drawn from the social insect literature (mostly from ants, for which there is the best data) to illustrate concepts or trends and make a number of predictions concerning how a particular trait is expected to correlate with other aspects of social complexity. Within each section we also expand the scope of the arguments to consider these relationships in a much broader sense of'sociality' by drawing parallels with other ,social' entities such as multicellular individuals, which can be understood as ,societies' of cells. The aim is to draw out any parallels and common causal relationships among the correlates. Two themes run through the study. The first is the role of colony size as an important factor affecting social complexity. The second is the complexity of individual workers in relation to the complexity of the colony. Consequently, this is an ideal opportunity to test a previously proposed hypothesis that ,individuals of highly social ant species are less complex than individuals from simple ant species' in light of numerous social correlates. Our findings support this hypothesis. In summary, we conclude that, in general, complex societies are characterized by large colony size, worker polymorphism, strong behavioural specialization and loss of totipotency in its workers, low individual complexity, decentralized colony control and high system redundancy, low individual competence, a high degree of worker cooperation when tackling tasks, group foraging strategies, high tempo, multi-chambered tailor-made nests, high functional integration, relatively greater use of cues and modulatory signals to coordinate individuals and heterogeneous patterns of worker-worker interaction. Key words: Ants, insect societies, individual complexity, social complexity, polyphenism, totitpotency, work organization, functional integration, sociality. [source] Genetic analysis of phenotypes derived from longitudinal data: Presentation Group 1 of Genetic Analysis Workshop 13GENETIC EPIDEMIOLOGY, Issue S1 2003Konstantin Strauch Abstract The participants of Presentation Group 1 used the GAW13 data to derive new phenotypes, which were then analyzed for linkage and, in one case, for association to the genetic markers. Since the trait measurements ranged over longer time periods, the participants looked at the time dependence of particular traits in addition to the trait itself. The phenotypes analyzed with the Framingham data can be roughly divided into 1) body weight-related traits, which also include a type 2 diabetes progression trait, and 2) traits related to systolic blood pressure. Both trait classes are associated with metabolic syndrome. For traits related to body weight, linkage was consistently identified by at least two participating groups to genetic regions on chromosomes 4, 8, 11, and 18. For systolic blood pressure, or its derivatives, at least two groups obtained linkage for regions on chromosomes 4, 6, 8, 11, 14, 16, and 19. Five of the 13 participating groups focused on the simulated data. Due to the rather sparse grid of microsatellite markers, an association analysis for several traits was not successful. Linkage analysis of hypertension and body mass index using LODs and heterogeneity LODs (HLODs) had low power. For the glucose phenotype, a combination of random coefficient regression models and variance component linkage analysis turned out to be strikingly powerful in the identification of a trait locus simulated on chromosome 5. Haseman-Elston regression methods, applied to the same phenotype, had low power, but the above-mentioned chromosome 5 locus was not included in this analysis. Genet Epidemiol 25 (Suppl. 1):S5,S17, 2003. © 2003 Wiley-Liss, Inc. [source] Are there correlates of male Australian Magpie Gymnorhina tibicen reproductive success in a population with high rates of extra-group paternity?IBIS, Issue 2 2006KATE L. DURRANT The reproductive success of a male bird is often correlated with measurable traits that predict his intrinsic quality. Females are thought to base their selection of mates on the latter's ,quality' in order to gain their ,good genes'. Male Australian Magpies Gymnorhina tibicen of the white-backed race tyrannica were trapped in two breeding seasons. Measurements were taken of morphometric and other characteristics in order to discover whether particular traits of males were associated with: (1) percentage of offspring sired in the territory, (2) number of fledglings produced in the territory per season and (3) whether females select males for their ,good genes'. There were no consistently significant correlations between any of the measured variables and male Magpie reproductive success within territories. In particular, none of the traits measured had any consistent correlation with the percentage of offspring sired in a territorial group. This was an unexpected result given that the species is strongly territorial but also engages regularly in extra-group copulations. These findings appear contrary to the predictions of the ,good genes' hypothesis. The general lack of correlation between the variables and level of genetic paternity may in fact be due to females engaging in extra-group mating primarily to avoid breeding with a close relative rather than to choose a high-quality male. In this case, males would not have to be ,high quality', but merely genetically different from the female's social mate. [source] Eco-evolutionary vs. habitat contributions to invasion in salmon: experimental evaluation in the wildMOLECULAR ECOLOGY, Issue 1 2008MICHAEL T. KINNISON Abstract Although trait evolution over contemporary timescales is well documented, its influence on ecological dynamics in the wild has received much less attention particularly compared to traditional ecological and environmental factors. For example, evolution over ecologically relevant timescales is expected in populations that colonize new habitats, where it should theoretically enhance fitness, associated vital rates of survival and reproduction, and population growth potential. Nonetheless, success of exotic species is much more commonly attributed to ecological aspects of habitat quality and ,escape from enemies' in the invaded range. Here, we consider contemporary evolution of vital rates in introduced Chinook salmon (Oncorhynchus tshawytscha) that quickly colonized New Zealand and diverged over c. 26 generations. By using experimental translocations, we partitioned the roles of evolution and habitat quality in modifying geographical patterns of vital rates. Variation in habitat quality within the new range had the greatest influence on broad geographical patterns of vital rates, but locally adapted salmon still exhibited more than double the vital rate performance, and hence fitness, of nonlocal counterparts. The scope of this fitness evolution far exceeds the scale of divergence in trait values for these populations, or even the expected fitness effects of particular traits. These results suggest that contemporary evolution can be an important part of the eco-evolutionary dynamics of invasions and highlight the need for studies of the emergent fitness and ecological consequences of such evolution, rather than just changes in trait values. [source] Estimation of dominance genetic variances for reproductive traits and growth traits of calves in Japanese Black cattleANIMAL SCIENCE JOURNAL, Issue 4 2004Takafumi ISHIDA ABSTRACT The dominance genetic effects for reproductive and calf growth abilities in the practical Japanese Black populations were examined using average information (AI) algorithm restricted maximum likelihood (REML) under animal models. The reproductive traits were observed in Japanese Black cattle maintained at Tottori and Okinawa prefectures, and growth traits of calves were observed in cattle at Okinawa. The average of dominance relationships in Tottori ranged from 0.2 to 0.4%, while the level in Okinawa was lower and sparse compared with Tottori. The proportions of the dominance variances to sum of additive and dominance variances () were all 0.02 for reproductive traits in Tottori. In contrast, the proportion was 0.02,0.64 in Okinawa regardless of the level of dominance relationships. These proportions suggested that the dominance might affect the expression of calving interval, days open and gestation length in Okinawa, where breeding units were spread over many islands. Although the dominance variances could not estimate birthweight, w as 0.34 for calf market weight and 0.27 for average daily gain from birth to calf market in Okinawa. These values also suggested that the dominance might affect the early growth of calves. In the near future, genetic relationships will become more complicated with continuation of the current selection and mating systems. Therefore, genetic evaluation accounting for dominance effects would be necessary for particular traits and populations. [source] The complex oral microflora of high-risk individuals and groups and its role in the caries processCOMMUNITY DENTISTRY AND ORAL EPIDEMIOLOGY, Issue 4 2005David Beighton Abstract , The involvement of the oral biofilm in the caries process requires re-evaluation. The essential role of mutans streptococci (Streptococcus mutans and Streptococcus sobrinus) in the caries process is not proven. Acid production by dental plaque is not dependent upon the presence of mutans streptococci; caries occurs in the absence of these species and their presence does not necessarily indicate caries activity. Other oral bacteria, non-mutans streptococci, Actinomyces spp. and Bifidobacterium spp., are acidogenic and aciduric. They outnumber mutans streptococci in dental plaque, and there are data which support a role for these bacteria in the initiation and progression of caries. Molecular studies demonstrate the great diversity and complexity of the flora associated with caries. Many taxa identified have not been cultured and the role of these taxa is not known. We have, in mutans streptococci, good markers of disease but not necessarily the aetiological agents of the disease. Considerably more research is required to investigate the transition of tooth surfaces from being intact and sound to the white spot lesion stage. A combination of conventional and molecular approaches are required to elucidate the involvement of an individual taxon and of microbial populations with particular traits in the caries process. [source] | ||||||||||