Importance Of Different Traits Research Articles

Integrating multiple plant functional traits to predict ecosystem productivity

Quantifying and predicting variation in gross primary productivity (GPP) is important for accurate assessment of the ecosystem carbon budget under global change. Scaling traits to community scales for predicting ecosystem functions (i.e., GPP) remain challenging, while it is promising and well appreciated with the rapid development of trait-based ecology. In this study, we aim to integrate multiple plant traits with the recently developed trait-based productivity (TBP) theory, verify it via Bayesian structural equation modeling (SEM) and complementary independent effect analysis. We further distinguish the relative importance of different traits in explaining the variation in GPP. We apply the TBP theory based on plant community traits to a multi-trait dataset containing more than 13,000 measurements of approximately 2,500 species in Chinese forest and grassland systems. Remarkably, our SEM accurately predicts variation in annual and monthly GPP across China (R2 values of 0.87 and 0.73, respectively). Plant community traits play a key role. This study shows that integrating multiple plant functional traits into the TBP theory strengthens the quantification of ecosystem primary productivity variability and further advances understanding of the trait-productivity relationship. Our findings facilitate integration of the growing plant trait data into future ecological models.

Survey data to identify the selection criteria used by breeders of four strains of Pakistani beetal goats.

This article presents raw data from a survey conducted to identify the selection criteria of breeders raising either of four strains of Beetal goats, namely Beetal Faisalabadi, Beetal Makhi-Cheeni, Beetal Nuqri, and Beetal Rahim Yar Khan. After a pre-survey, a questionnaire was developed and a survey was conducted at four sites of the Punjab province of Pakistan: Faisalabad/Sahiwal, Bahawalpur/Bahawalnagar, Rajanpur, and Rahim Yar Khan. Each of these sites was the home tract of one strain. During the survey breeders (n = 162) were asked to rank the traits of their selection criteria based on the relative importance of those traits. Furthermore, the prevailing production system was also characterized by the breeders. For the interpretation of the results of this survey the readers are referred to Ref. [1]. The raw data set provided in this article can be extended in the future to include more strains of Beetal goats as well as other goat breeds. The selection criteria of breeders can change over time. This data set can also be used in future studies to investigate the temporal changes in the relative importance of different traits for the breeders. The factors potentially influencing those changes can also be investigated. This data set can further be utilized to design community based breeding plans tailored to the needs of the goat farming community.

Men Should Be Competent, Women Should Have it All: Multiple Criteria in the Evaluation of Female Job Candidates

The present research investigated whether evaluations of female and male job candidates rely on different dimensions. Going beyond previous studies on the role of gender stereotypes, we examined the relative importance of competence, morality, and sociability in employment decisions. In Study 1, we content-analyzed 68 archival reports of professionals to explore the extent to which they spontaneously referred to the three dimensions in evaluations of women and men. In Study 2, 259 Italian student participants rated the importance of different traits in hiring a female or male candidate for a job position. Additionally, we tested the relative influence of specific information about candidate competence and morality in predicting hiring (Study 3; n = 123 Italian students) and contract renewal (Study 4; n = 108 Italian students) decisions. Findings consistently showed that competence was the most important dimension in evaluations and decisions concerning male candidates, whereas all dimensions were important for female candidates. Moreover, decisions concerning women were influenced by the dimension on which they appeared to be relatively weak. Overall, findings suggest that women are evaluated against multiple criteria and might therefore be asked to meet more requirements than men to be selected and make a career. These findings can help evaluators and decision makers adopt assessment strategies that prevent more critical evaluations of women, such as establishing specific evaluation criteria before the disclosure of a candidate’s gender.

Assessing trait contribution and mapping novel QTL for salinity tolerance using the Bangladeshi rice landrace Capsule

BackgroundSalinity is one of the most widespread abiotic stresses affecting rice productivity worldwide. The purpose of this study was to establish the relative importance of different traits associated with salinity tolerance in rice and to identify new quantitative trait loci (QTL) conferring tolerance to salinity at seedling stage. A total of 231 F2:3 plants derived from a cross between a sensitive variety BRRI dhan29 (BR29 hereafter) and Capsule, a salt tolerant Bangladeshi indica landrace, were evaluated under salt stress in a phytotron.ResultsOut of the 231 F2 plants, 47 highly tolerant and 47 most sensitive lines were selected, representing the two extreme tails of the phenotypic distribution. These 94 plants were genotyped for 105 simple sequence repeat (SSR) and insertion/deletion (InDel) markers. A genetic linkage map spanning approximately 1442.9 cM of the 12 linkage groups with an average marker distance of 13.7 cM was constructed. QTL were identified on the long arm of chromosome 1 for Na+ concentration, K+ concentration, Na+-K+ ratio and survival; chromosome 3 for Na+ concentration, survival and overall phenotypic evaluation using the Standard Evaluation system (SES); and chromosome 5 for SES. A total of 6 pairwise epistatic interactions were also detected between QTL-linked and QTL-unlinked regions. Graphical genotyping indicated an association between the phenotypes of the extreme families and their QTL genotypes. Path coefficient analysis revealed that Na+ concentration, survival, Na+-K+ ratio and the overall phenotypic performance (SES score) are the major traits associated with salinity tolerance of Capsule.ConclusionsCapsule provides an alternative source of salinity tolerance aside from Pokkali and Nona Bokra, the two Indian salt tolerant landraces traditionally used for breeding salt tolerant rice varieties. Pyramiding the new QTL identified in this study with previously discovered loci, such as Saltol, will facilitate breeding varieties that are highly tolerant of salt stress.

Evolution of the selfing syndrome: Anther orientation and herkogamy together determine reproductive assurance in a self-compatible plant.

Capacity for autonomous self-fertilization provides reproductive assurance, has evolved repeatedly in the plant kingdom, and typically involves several changes in flower morphology and development (the selfing syndrome). Yet, the relative importance of different traits and trait combinations for efficient selfing and reproductive success in pollinator-poor environments is poorly known. In a series of experiments, we tested the importance of anther-stigma distance and the less studied trait anther orientation for efficiency of selfing in the perennial herb Arabis alpina. Variation in flower morphology among eight self-compatible European populations was correlated with efficiency of self-pollination and with pollen limitation in a common-garden experiment. To examine whether anther-stigma distance and anther orientation are subject to directional and/or correlational selection, and whether this is because these traits affect pollination success, we planted a segregating F2 population at two native field sites. Selection strongly favored a combination of introrse anthers and reduced anther-stigma distance at a site where pollinator activity was low, and supplemental hand-pollination demonstrated that this was largely because of their effect on securing self-pollination. The results suggest that concurrent shifts in more than one trait can be crucial for the evolution of efficient self-pollination and reproductive assurance in pollinator-poor habitats.

What explains patterns of biodiversity across the Tree of Life?: New research is revealing the causes of the dramatic variation in species numbers across branches of the Tree of Life.

A major challenge in biology is to explain why some groups have thousands or millions of species whereas others have few. Here, I review the causes of this variation. New studies reveal that higher species numbers in many major groups are explained by higher diversification rates (and traits that accelerate these rates). These traits span most of biology (e.g. genomics, ecology, morphology). Rather than simply testing individual traits, research should now focus on comparing how much variation in diversification rates is explained by different types of traits. For example, is local-scale ecology (e.g. microhabitat, diet) more important than large-scale climate (e.g. occurring in tropical vs. temperate regions)? Are traits based on particular values (e.g. smaller body sizes) more important than those based on rates of change (e.g. faster size evolution)? I review recent results on the relative importance of different traits for driving diversification, and present a framework for future research.

Foliar phosphorus content predicts species relative abundance in P-limited Tibetan alpine meadows

Traits that favor rapid plant growth are expected to have an important influence on species relative abundance (SRA) in semi-natural grasslands where competitive exclusion is reduced by grazing. However, which traits are more strongly associated with variation in SRA remains largely unknown, especially in P-limited but species-rich grasslands. We assessed the relative importance of traits predicting SRA in P-limited Tibetan alpine meadows subject to long term grazing. We assessed abundance in terms of both aboveground biomass and ramet numbers in relation to seven traits (specific leaf area, LDMC: leaf dry matter content, leaf carbon concentration, leaf nitrogen concentration, LPC: leaf phosphorus concentration, mature height, and seed size) for all component species in grazed and ungrazed plots in each of three contrasting sites on the Tibetan Plateau. We used CATS regression (i.e. regression for Community Assembly through Trait Selection) to quantify the relative importance of different traits in predicting SRA, and tested dependence of trait importance values on both environmental context and alternative measures of abundance. Species were primarily differentiated along a trade-off axis involving traits promoting nutrient acquisition for fast growth vs resource conservation and competitive ability. A higher LPC consistently was the most important trait predicting species abundance in grazed plots, while species with low LPC but higher LDMC held an advantage in ungrazed plots. This suggests that in competition-released communities, species with a high ability to uptake soil available P tend to become abundant, while in competition-dominated communities, species using fixed P efficiently do better. The relative importance of traits in ungrazed plots did not change across sites, but in grazed plots species that have traits associated with nutrient conservation were favored in colder and drier conditions. The results highlight the importance of traits affecting acquisition of soil available P in these Tibetan alpine meadow communities. Species tradeoffs in nutrient acquisition versus conservation are a primary determinant of SRA, but the relative importance of traits depended on both environmental context and whether SRA was estimated as above-ground biomass or as number of ramets.

Individual traits as determinants of time to death under extreme drought in Pinus sylvestris L.

Plants exhibit a variety of drought responses involving multiple interacting traits and processes, which makes predictions of drought survival challenging. Careful evaluation of responses within species, where individuals share broadly similar drought resistance strategies, can provide insight into the relative importance of different traits and processes. We subjected Pinus sylvestris L. saplings to extreme drought (no watering) leading to death in a greenhouse to (i) determine the relative effect of predisposing factors and responses to drought on survival time, (ii) identify and rank the importance of key predictors of time to death and (iii) compare individual characteristics of dead and surviving trees sampled concurrently. Time until death varied over 3 months among individual trees (from 29 to 147 days). Survival time was best predicted (higher explained variance and impact on the median survival time) by variables related to carbon uptake and carbon/water economy before and during drought. Trees with higher concentrations of monosaccharides before the beginning of the drought treatment and with higher assimilation rates prior to and during the treatment survived longer (median survival time increased 25-70 days), even at the expense of higher water loss. Dead trees exhibited less than half the amount of nonstructural carbohydrates (NSCs) in branches, stem and relative to surviving trees sampled concurrently. Overall, our results indicate that the maintenance of carbon assimilation to prevent acute depletion of NSC content above some critical level appears to be the main factor explaining survival time of P. sylvestris trees under extreme drought.

Functional traits as predictors of vital rates across the life cycle of tropical trees

SummaryThe ‘functional traits’ of species have been heralded as promising predictors for species’ demographic rates and life history. Multiple studies have linked plant species’ demographic rates to commonly measured traits. However, predictive power is usually low – raising questions about the practical usefulness of traits – and analyses have been limited to size‐independent univariate approaches restricted to a particular life stage.Here we directly evaluated the predictive power of multiple traits simultaneously across the entire life cycle of 136 tropical tree species from centralPanama. Using a model‐averaging approach, we related wood density, seed mass, leaf mass per area and adult stature (maximum diameter) to onset of reproduction, seed production, seedling establishment, and growth and survival at seedling, sapling and adult stages.Three of the four traits analysed here (wood density, seed mass and adult stature) typically explained 20–60% of interspecific variation at a given vital rate and life stage. There were strong shifts in the importance of different traits throughout the life cycle of trees, with seed mass and adult stature being most important early in life, and wood density becoming most important after establishment. Every trait had opposing effects on different vital rates or at different life stages; for example, seed mass was associated with higher seedling establishment and lower initial survival, wood density with higher survival and lower growth, and adult stature with decreased juvenile but increased adult growth and survival.Forest dynamics are driven by the combined effects of all demographic processes across the full life cycle. Application of a multitrait and full‐life cycle approach revealed the full role of key traits, and illuminated how trait effects on demography change through the life cycle. The effects of traits on one life stage or vital rate were sometimes offset by opposing effects at another stage, revealing the danger of drawing broad conclusions about functional trait–demography relationships from analysis of a single life stage or vital rate. Robust ecological and evolutionary conclusions about the roles of functional traits rely on an understanding of the relationships of traits to vital rates across all life stages.

Determinants of plant establishment success in a multispecies introduction experiment with native and alien species

Determinants of plant establishment and invasion are a key issue in ecology and evolution. Although establishment success varies substantially among species, the importance of species traits and extrinsic factors as determinants of establishment in existing communities has remained difficult to prove in observational studies because they can be confounded and mask each other. Therefore, we conducted a large multispecies field experiment to disentangle the relative importance of extrinsic factors vs. species characteristics for the establishment success of plants in grasslands. We introduced 48 alien and 45 native plant species at different seed numbers into multiple grassland sites with or without experimental soil disturbance and related their establishment success to species traits assessed in five independent multispecies greenhouse experiments. High propagule pressure and high seed mass were the most important factors increasing establishment success in the very beginning of the experiment. However, after 3 y, propagule pressure became less important, and species traits related to biotic interactions (including herbivore resistance and responses to shading and competition) became the most important drivers of success or failure. The relative importance of different traits was environment-dependent and changed over time. Our approach of combining a multispecies introduction experiment in the field with trait data from independent multispecies experiments in the greenhouse allowed us to detect the relative importance of species traits for early establishment and provided evidence that species traits--fine-tuned by environmental factors--determine success or failure of alien and native plants in temperate grasslands.

An integrative modeling approach to elucidate suction-feeding performance

Research on suction-feeding performance has mostly focused on measuring individual underlying components such as suction pressure, flow velocity, ram or the effects of suction-induced forces on prey movement during feeding. Although this body of work has advanced our understanding of aquatic feeding, no consensus has yet emerged on how to combine all of these variables to predict prey-capture performance. Here, we treated the aquatic predator-prey encounter as a hydrodynamic interaction between a solid particle (representing the prey) and the unsteady suction flows around it, to integrate the effects of morphology, physiology, skull kinematics, ram and fluid mechanics on suction-feeding performance. We developed the suction-induced force-field (SIFF) model to study suction-feeding performance in 18 species of centrarchid fishes, and asked what morphological and functional traits underlie the evolution of feeding performance on three types of prey. Performance gradients obtained using SIFF revealed that different trait combinations contribute to the ability to feed on attached, evasive and (strain-sensitive) zooplanktonic prey because these prey types impose different challenges on the predator. The low overlap in the importance of different traits in determining performance also indicated that the evolution of suction-feeding ability along different ecological axes is largely unconstrained. SIFF also yielded estimates of feeding ability that performed better than kinematic traits in explaining natural patterns of prey use. When compared with principal components describing variation in the kinematics of suction-feeding events, SIFF output explained significantly more variation in centrarchid diets, suggesting that the inclusion of more mechanistic hydrodynamic models holds promise for gaining insight into the evolution of aquatic feeding performance.

Pheno-morphological, agronomic and genetic diversity among natural populations of sulla (Hedysarum coronarium L.) collected in Sicily, Italy

Sulla (Hedysarum coronarium L.) is a short-lived perennial forage legume that plays a key role in cereal-based systems in semi-arid Mediterranean regions, particularly in organic production and low-input oriented agriculture. In Sicily, the species is widespread both as a wild and cultivated plant. The present study assessed the phenotypic and genetic variation among natural populations of sulla collected from different environments throughout Sicily and analysed how the patterns of phenotypic diversity varied according to the environmental parameters of each collection site. Two commercial varieties and two Sicilian agro-ecotypes were also included in the study as controls. Principal components analysis (PCA) was performed on the sites using geographic, climatic, and pedological data to assess the differences in types of collection sites. PCA was also performed on the accessions (using pheno-morphological and agronomic data) to establish the importance of different traits in explaining multivariate polymorphisms. The results showed a large degree of genetic diversity (based on ISSR markers) and variability in pheno-morphological and agronomic traits. PCA did not clearly differentiate the accessions according to their habitats of origin, but in some cases accessions from the same habitat had a tendency to group together. The agronomic attributes of several populations were more pronounced than those of the controls. The observed variability may be valuable when selecting for H. coronarium varieties suitable for various uses (e.g., hay production, grazing, soil protection).

Variation in pheno-morphological and agronomic traits among burr medic (Medicago polymorpha L.) populations collected in Sicily, Italy

The present study assessed the diversity of pheno-morphological and agronomic traits among 31 natural populations of burr medic (Medicago polymorpha L.) from different environments throughout Sicily, and analysed the patterns of phenotypic diversity in relation to the environmental parameters of each collection site. Three commercial cultivars (Cavalier, Santiago, and Anglona) were also included in the study as check cultivars. Two field experiments were performed in 2005–06 in a hilly area of the Sicilian inland. Principal components analysis (PCA) was performed on the sites using geographic, climatic, and pedological data to assess the differences in types of collection sites. PCA was also performed on the accessions using pheno-morphological and agronomic data to establish the importance of different traits in explaining multivariate polymorphisms. Sicilian burr medic populations showed highly significant inter-population differences for all of the recorded pheno-morphological and agronomic traits, and several populations had agronomic attributes that were more pronounced than those of the check cultivars. PCA did not clearly differentiate the accessions according to their habitats of origin, but in some cases, accessions from the same habitat had a tendency to stay together. Populations from drier and warmer habitats flowered earlier and were less productive than those from wetter and colder ones. The large variability in both pheno-morphological and agronomic traits among Sicilian populations may be valuable when searching for suitable M. polymorpha material to exploit in pastures and crop–livestock farming systems in the Mediterranean region.

Identifying superior wheat cultivars in participatory research on resource poor farms

Improving livelihood of resource poor farmers is an important goal of wheat research in developing countries. Although remarkable success has been achieved to date in developing widely adapted wheat cultivars, many resource poor farmers in marginal areas in developing world have not benefited. Participatory research could greatly enhance identifying cultivars according to the choice of the poor farmers. This study was conducted to examine how farmers’ selection criteria could assist breeders in identifying superior wheat cultivars, and determine if a new statistical analysis tool, GGE biplot, could be effectively used in selection of improved cultivar based on quantitative (grain yield) and qualitative data (farmers’ preference score). The field experiments were conducted in 3 years (2003–2005) in three mid-hill districts in the central Nepal involving resource poor wheat farmers. Sixteen wheat genotypes, including a long-term and a current commercial cultivar, were used in the study. Data were collected on agronomic traits considered important by the participating farmers. These included days to heading and maturity, plant height, effective tiller number, spike length, kernel per spike, 1000-kernel weight and grain yield. Farmers also qualitatively scored each genotype for multiple traits based on their preference. In general, the farmers used the same traits in selecting a superior cultivar that are used by breeders. However, relative importance of different traits differed, not necessarily following in line with the breeder preference. The cultivar superiority based on quantitative agronomic data (breeders’ criteria) and qualitative preference scores (farmers’ criteria) often showed synergies, however, there were differences as well. This indicates farmers’ ability to choose superior cultivars based on qualitative observation compared to tedious quantitative data recording in the on-station testing. In the first year, a greater number of farmers selected improved check as a better choice than recent advanced breeding lines. In the 2nd and 3rd years, the farmers preferred genotypes other than the checks. This underlines the importance of testing of advanced materials in farmers’ fields in multiple years. Principal component analysis using GGE-biplot was useful in identifying superior genotypes based on both quantitative and qualitative data recorded across environments. This approach could be useful in analyzing data from participatory agricultural research conducted under highly diverse farmers’ field conditions where it is easier to record observations on qualitative than quantitative scale. This technique can also be extended to on-farm participatory testing of other technologies. The findings bear implications for a broad range of participatory research and technology evaluation and verification.

Effects of soil properties on variation in growth, grain yield and nutrient concentration of wheat and barley

High spatial and temporal variability is an inherent feature of dryland cereal crops over much of the southern cereal zone. The potential limitations to crop growth and yield of the chemical properties of the subsoils in the region have been long recognised, but there is still an incomplete understanding of the relative importance of different traits and how they interact to affect grain yield. Measurements were taken in a paddock at the Minnipa Agriculture Centre, Upper Eyre Peninsula, South Australia, to describe the effects of properties in the topsoil and subsoil on plant dry matter production, grain yield and plant nutrient concentrations in two consecutive years. Wheat (Triticum aestivum L. cv. Worrakatta) was grown in the first year and barley (Hordeum vulgare L. cv. Barque) in the second. All soil properties except pH showed a high degree of spatial variability. Variability in plant nutrient concentration, plant growth and grain yield was also high, but less than that of most of the soil properties. Variation in grain yield was more closely related to variation in dry matter at maturity and in harvest index than to dry matter production at tillering and anthesis. Soil properties had a stronger relationship with dry matter production and grain yield in 1999, the drier of the two years. Colwell phosphorus concentration in the topsoil (0–0.15 m) was positively correlated with dry matter production at tillering but was not related to dry matter production at anthesis or with grain yield. Subsoil pH, extractable boron concentration and electrical conductivity (EC) were closely related. The importance of EC and soil extractable boron to grain yield variation increased with depth, but EC had a greater influence than the other soil properties. In a year with above-average rainfall, very little of the variation in yield could be described by any of the measured soil variables. The results suggest that variation in EC was more important to describing variation in yield than variation in pH, extractable boron or other chemical properties.

Sexual signaling in the European bitterling: females learn the truth by direct inspection of the resource

In many taxa females appear to base their mate choice on multiple traits. But the relative importance of different traits in mate choice has rarely been determined. Here we show that females of a freshwater fish, the European bitterling, Rhodeus sericeus, base their mate choice on multiple traits that differ in their reliability as indicators of expected reproductive success and are used at different stages of the decision process. The initial decision to inspect a male is based on male behavior and red coloration, whereas the final spawning decision is based on the quality of the live unionid mussel, Anodonta anatina, that the male is defending as an oviposition site. Male traits may indicate which males are worth inspecting by reflecting male quality, such as reproductive condition and genetic constitution. Male traits do not, however, reflect mussel quality, as bright males also court females vigorously toward mussels that yield a low probability of survival of the offspring. Females, on the other hand, are choosier than males in their choice of spawning site and seem to gain reliable information about the survival probability of the eggs by inspecting the mussel directly. Key words: bitterlings, mate choice, multiple ornaments, reliable signaling, resource quality, Rhodeus sericeus, sexual selection. [Behav Ecol 12:407–411 (2001)]

The Relative Economic Importance of Traits Measured in the Random Sample Egg Laying Tests

Newer data of random sample egg laying tests held in Japan from 1965 to 1967 were analysed to know the ralative economic importance of each of the traits considered and to see if there are any changes in relative economic importance of different traits compared with the results of previous analysis.The multiple regression with 500-day feed conversion, egg production rate, laying, viability, egg weight and growing viability explained 89.8% of 500-day income variation. Feed conversion was the most important trait followed by egg production rate, laying viability, egg weight and growing viability in the order mentioned. Since the relative importance of egg production rate and egg weight was greater than in the previous data, rank of characters in their relative importance became more similar to the U.S. data (1963-1965) analysed previously.In 270- and 300-day records, egg production rate and egg mass improved considerably during this three-year period, while no changes in 500-day production rate, egg mass and feed conversion were recognized, suggesting a change of production pattern.Five hundred-day income was predicted by 270- and 300-day records, too. Sixty four percent and 72% of income variation were explained by 270- and 300 day records, respectively. It was noticed that partial regression coefficient of income on age at 50% production was negligible in 500-day record, but in part records it took positive values. This means that, among the birds showing the same production by 270- or 300 days of age, early maturing ones tend to produce less in the later stage of the test period than late maturing ones.Use of part records was studied, and rather mild culling with part records was recommended.

Selection for economic characters in Australian Merino sheep. V. Further estimates of phenotypic and genetic parameters.

Estimates of heritability, genetic correlations, phenotypic correlations, and other parameters among eight characteristics were obtained from Merino sheep at Trangie Agricultural Experiment Station. One set of estimates was obtained by parent-offspring regressions from data obtained between 1943 and 1952. Another set was obtained by half-sib analyses from data from sheep with first adult shearings in 1953. Estimates of heritability were: greasy fleece weight, 0.40 ± 0.06; yield (per cent.), 0.39 ± 0.07; clean fleece weight, 0.47 ± 0.07; staple length, 0.56 � 0.07; crimps per inch, 0.47 ± 0.11; folds, 0.50 ± 0.07; body weight, 0.36 ± 0.08; birthcoat, 0.80 ± 0.10. The most important genetic correlation limiting genetic improvement in clean fleece weight is that between this trait and crimps per inch. Because of this the rate of improvement in fleece weight could be reduced by about 30 per cent. whenever crimps per inch is also selected. Other genetic correlations indicate antagonisms between characteristics, but these antagonisms appear to be of minor importance except that between clean fleece weight and crimps per inch. This sheep population does not appear to have reached a state of genetic homeostasis, a t least with respect to the characteristics studied. However, the findings emphasize the necessity for careful evaluation of the economic importance of different traits, and for accurate measurement, if maximum genetic progress is to be achieved.