			Home About us Contact

Size Traits (size + trait)

Distribution by Scientific Domains

Life Sciences	80%

Selected Abstracts

Size traits and site conditions determine changes in seed bank structure caused by grazing exclusion in semiarid annual plant communities

ECOGRAPHY, Issue 1 2006
Yagil Osem
1. Contrasting patterns of change in the seed bank of natural grasslands are frequently found in response to grazing by domestic herbivores. Here, we studied the hypotheses that a) patterns of change in seed bank density and composition in response to grazing depend on spatial variation in resource availability and productivity, and b) that variation among species in patterns of seed bank response to grazing is linked to differences in species size traits (i.e. size of plant, dispersal unit and seed). 2. Effects of sheep grazing exclusion on the seed bank were followed during five years in a semiarid Mediterranean annual plant community in Israel. Seed bank density and composition were measured in autumn, before the rainy season, inside and outside fenced exclosures in four neighboring topographic sites differing in vegetation characteristics, soil resources and primary productivity: Wadi (dry stream terraces, high productive site), Hilltop, South- and North-facing slopes (less productive sites). 3. Topographic sites differed in seed density (range ca 2500,18000 seed m,2) and in seed bank response to grazing exclusion. Fencing increased seed density by 78, 51 and 18% in the Wadi, South- and North-facing slopes, respectively, but had no effect in the Hilltop. At the species level, grazing exclusion interacted with site conditions in determining species seed bank density, with larger or opposite changes in the high productive Wadi compared to the other less productive sites. 4. Changes in seed bank structure after grazing exclusion were strongly related to species size traits. Grazing exclusion favored species with large size traits in all sites, while seed density of tiny species decreased strongly in the high productive Wadi. Species with medium and small size traits showed lesser or no responses. 5. The size of plants, dispersal units and seeds were strongly correlated to each other, thus confounding the evaluation of the relative importance of each trait in the response of species to grazing and site conditions. We propose that the relative importance of plant size vs seed size in the response to grazing changes with productivity level. [source]

Contribution of direct and maternal genetic effects to life-history evolution

NEW PHYTOLOGIST, Issue 3 2009
Laura F. Galloway
Summary ,,Maternal effects are ubiquitous in nature. In plants, most work has focused on the effects of maternal environments on offspring trait expression. Less is known about the prevalence of genetic maternal effects and how they influence adaptive evolution. Here, we used multivariate genetic models to estimate the contributions of maternal and direct genetic (co)variance, the cross-generation direct-maternal covariance, and M, the matrix of maternal effect coefficients, for life-history traits in Campanulastrum americanum, a monocarpic herb. ,,Following a three-generation breeding design, we grew paternal half-sib families with full-sib relatives of each parent and measured juvenile and adult traits. ,,Seed size was influenced exclusively by maternal environmental effects, whereas maternal genetic effects influenced traits throughout the life cycle, including strong direct and maternal additive genetic correlations within and between generations for phenological and size traits. Examination of M suggested that both juvenile and adult traits in maternal plants influenced the expression of offspring traits. ,,This study reveals substantial potential for genetic maternal effects to contribute to adaptive evolution including cross-generation direct-maternal correlations that may slow selection response, maternal effects on phenology that reinforce genetic correlations, and within- and between-generation genetic correlations that may influence life-history polymorphism. [source]

Mechanisms of Regulation of Litter Size in Pigs on the Genome Level

REPRODUCTION IN DOMESTIC ANIMALS, Issue 2007
O Distl
Contents Improvement in litter size has become of great interest in pig industry as good fecundity is directly related to a sow's productive life. Genetic regulation of litter size is complex and the main component traits so far defined are ovulation rate, embryonic survival, uterus capacity, foetal survival and pre-weaning losses. Improvements using concepts of the quantitative genetics let expect only slow genetic progress due to its low heritability of approximately 0.09 for number of piglets born alive. Marker assisted selection allows to dissect litter size in its component traits and using molecular genetic markers for the components of litter size traits promises more progress and advantages in optimum balancing of the different physiological mechanisms influencing litter size. In this review, efforts being made to unravel the genetic determinants of litter size are accounted and discussed. For litter size traits, more than 50 quantitative trait loci (QTL) were mapped and in more than 12 candidate genes associations confirmed. The number of useful candidate genes is much larger as shown by expression profiles and in addition, much more QTL can be assumed. These functional genomic approaches, both QTL mapping and candidate gene analysis, have to be merged for a better understanding of a wider application across different pig breeds and lines. Newly developed tools based on microarray techniques comprising DNA variants or expressed tags of many genes or even the whole genome appear useful for in depth understanding of the genetics of litter size in pigs. [source]

Repeatability of size and fluctuating asymmetry of antler characteristics in red deer (Cervus elaphus) during ontogeny

BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2007
L. BARTO
Fluctuating asymmetry (FA) has been suggested as a measure of the sensitivity of development to a wide array of genetic and environmental stresses. It has been also suggested that antlers in red deer could be important during social and rutting displays. We used antler measurements of 51 males that were measured over subsequent seasons, from 3,8 years of age, and analysed three antler traits: antler weight, length, and the number of antler tines (antler size). We calculated absolute and relative FA. All three size traits were highly significantly intercorrelated. By contrast to this, the FA of the three traits, did not show such relationships. With increasing age, antler size and FA also increased. When testing the repeatability of FA and antler size, there was a principal difference in the pattern between FA and antler size, with the latter being much more consistent than the former. This suggests that antler size, not FA, may be a good predictor of the bearer's quality in mate selection. This fits well with the good-genes hypothesis that the development of extravagant secondary sexual characters can be an honest advertisement of heritable male quality. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 91, 215,226. [source]