Relationship of lower limb height to sitting height in black populations of Africa and the United States.

This article examines a recently reported generalization. Materials from more than a score of invetigations are drawn upon. These materials show there is not a substantial research base for the claim that interbreeding in the United States between black people of African ancestry and white people of European ancestry has resulted in increased lower limb height relative to sitting height.     

Construction of Selection Indexes with Restrictions

In this paper the problem of unistage selection with inequality constraints is formulated. If the predictor and criterion variables are all normally distributed, this problem can be written as a convex programming problem, with a linear objective function and with linear constraints and a quadratic constraint. Using the duality theory, for convex nonlinear programming it is proved, that its dual problem can be transformed into a convex minimization problem with non-negativity conditions. Good computational methods are known for solving this problem. By the help of the dual problem sufficient conditions for a solution of the original primal problem are derived and illustrated by an example of practical interest.     

Comparaisons des séquences d'ADN hautement répétées chez l'homme et diverses espèces de primates

Highly repeated DNA sequences from man, five other primate species and rat were compared using five restriction endonucleases. Calculations of a similarity index based on the mobility of various bands indicate that man, chimpanzee and baboons are very similar. The sequences of the genomes studied have apparently been reorganized during primate evolution.     

Determining the economic value of daily dry matter intake and associated methane emissions in dairy cattle

Feed represents a substantial proportion of production costs in the dairy industry and is a useful target for improving overall system efficiency and sustainability. The objective of this study was to develop methodology to estimate the economic value for a feed efficiency trait and the associated methane production relevant to Canada. The approach quantifies the level of economic savings achieved by selecting animals that convert consumed feed into product while minimizing the feed energy used for inefficient metabolism, maintenance and digestion. We define a selection criterion trait called Feed Performance (FP) as a 1 kg increase in more efficiently used feed in a first parity lactating cow. The impact of a change in this trait on the total lifetime value of more efficiently used feed via correlated selection responses in other life stages is then quantified. The resulting improved conversion of feed was also applied to determine the resulting reduction in output of emissions (and their relative value based on a national emissions value) under an assumption of constant methane yield, where methane yield is defined as kg methane/kg dry matter intake (DMI). Overall, increasing the FP estimated breeding value by one unit (i.e. 1 kg of more efficiently converted DMI during the cow’s first lactation) translates to a total lifetime saving of 3.23 kg in DMI and 0.055 kg in methane with the economic values of CAD $0.82 and CAD $0.07, respectively. Therefore, the estimated total economic value for FP is CAD $0.89/unit. The proposed model is robust and could also be applied to determine the economic value for feed efficiency traits within a selection index in other production systems and countries.     

Combined S2 and crossbred family selection in full-sib reciprocal recurrent selection

Summary A method (CRRS) that combines S₂ and crossbred family selection in full-sib reciprocal recurrent selection (FSRRS) is proposed. The method requires four generations per cycle in single-eared maize populations. Selection is based on performance of S₂ and full-sib families by applying selection index theory. Equations to estimate the coefficients included in the index are given. These estimates are functions of the genetic and phenotypic variances and covariances among and between the two kinds of families. Comparisons of FSRRS and CRRS under equivalent amount of effort show that CRRS has some advantage over FSRRS for low heritability of the trait being selected (e.g., maize yield) and when only one or two locations with two replications are involved in the selection experiment.Joint contribution: Institute Nacional de Investigaciones Agrarias, La Coruna, Spain; and Agricultural Research, Science and Education Administration, U.S. Department of Agriculture, and Journal Paper No. J-10118 of the Iowa Agriculture and Home Economics Experiment Station, Ames, IA 50011. Project 2194     

Critical manifolds,travelling waves,and an example from population genetics

A generalized Morse index theory is used to study travelling waves in a natural selection-migration model for a diploid organism when the selective strength is weak.     

Environmental and human factors influencing rare plant local occurrence, extinction and persistence: a 115-year study in the Mediterranean region

Aim Assessing whether environmental and human factors influenced the spatial distribution and the dynamics of regionally rare plant species since the late nineteenth century, and whether these spatial and temporal patterns of rare species occurrences differ according to their chorology (level of endemism and biogeographic affinity). Location An area extending over 6250 km² in the French Mediterranean Region. Methods We used two botanical surveys achieved in 1886 and in 2001, and considered species rare if occurring in only one or two sites in the study area. Each rare species was assigned to a group of endemism level (restricted endemic, non‐endemic), and of biogeographic affinity (Mediterranean, South/Central European, Mountain, Eurosiberian). A 1 × 1 km grid was applied to the study zone. Generalized linear models were developed to study the spatial distribution and the fate of rare species occurrences (local extinction vs. local persistence between 1886 and 2001), as a function of environmental and human variables. Multivariate analyses were used to test whether the spatial distribution and the fate of rare species occurrences differed according to their chorology. Results In 2001, rare species as a whole tended to occur at higher altitude, in zones dominated by semi‐natural open habitats, and where cultivated area had decreased in the last 30 years. Between 1886 and 2001, rare species were the most prone to local extinction in zones where human population density, cultivated area and livestock density had increased the most. Between 1886 and 2001, rare species had a higher probability of local persistence in zones of high altitude and steep slope, on basic bedrocks and with low cultivated area. Rare species with Mountain and Eurosiberian affinities occurred in marginal habitats in the study region, i.e. on gneiss‐micaschist bedrocks and at high altitudes, whereas Mediterranean and South/Central European rare species occupied more varied environmental conditions. Between 1886 and 2001, Eurosiberian rare species showed high rates of local extinction whereas Mediterranean rare species had a significantly higher probability of local persistence. Restricted endemic species mostly occurred in zones of high slope, low human population density, and where cultivated area had decreased in the last 30 years. Occurrences of restricted endemics remained significantly stable between 1886 and 2001. Main conclusions Environmental and land‐use changes that occurred over the twentieth century in the Mediterranean Basin had significant impacts on the spatial distribution and on the long‐term dynamics of rare species occurrences. Urbanization and recent agriculture intensification, occurring mainly in coastal plains and littoral zones, caused most local extinctions of rare species from 1886 to 2001. Local populations of Eurosiberian species, which reach their range limits in marginal zones of the Mediterranean, also appear to be highly vulnerable. Conversely, most restricted endemic species occur in habitats with harsh topography and low human disturbance and have a higher potential of local persistence.     

How do elevated CO2 and O3 affect the interception and utilization of radiation by a soybean canopy?

Net productivity of vegetation is determined by the product of the efficiencies with which it intercepts light (?_i) and converts that intercepted energy into biomass (?_c). Elevated carbon dioxide (CO₂) increases photosynthesis and leaf area index (LAI) of soybeans and thus may increase ?_i and ?_c; elevated O₃ may have the opposite effect. Knowing if elevated CO₂ and O₃ differentially affect physiological more than structural components of the ecosystem may reveal how these elements of global change will ultimately alter productivity. The effects of elevated CO₂ and O₃ on an intact soybean ecosystem were examined with Soybean Free Air Concentration Enrichment (SoyFACE) technology where large field plots (20‐m diameter) were exposed to elevated CO₂ (～550 μmol mol^?1) and elevated O₃ (1.2 × ambient) in a factorial design. Aboveground biomass, LAI and light interception were measured during the growing seasons of 2002, 2003 and 2004 to calculate ?_i and ?_c. A 15% increase in yield (averaged over 3 years) under elevated CO₂ was caused primarily by a 12% stimulation in ?_c , as ?_i increased by only 3%. Though accelerated canopy senescence under elevated O₃ caused a 3% decrease in ?_i, the primary effect of O₃ on biomass was through an 11% reduction in ?_c. When CO₂ and O₃ were elevated in combination, CO₂ partially reduced the negative effects of elevated O₃. Knowing that changes in productivity in elevated CO₂ and O₃ were influenced strongly by the efficiency of conversion of light energy into energy in plant biomass will aid in optimizing soybean yields in the future. Future modeling efforts that rely on ?_c for calculating regional and global plant productivity will need to accommodate the effects of global change on this important ecosystem attribute.     

Spectral composition of shade light in coastal-zone oak forests in SE Bulgaria,and relationships with leaf area index: a first overview

Major knowledge gaps exist with respect to light-quality regimes in the coastal-zone Strandzha Quercus frainetto (Q.f.) forest region adjoining the southern Bulgarian Black Sea. This paper presents preliminary results that help narrow these gaps. In conjunction with leaf area index (LAI) field campaigns we undertook measurements with an array of 7 broad-band (ca 40 nm) sensors covering the range 0.40–0.94 μm, plus 1 sensor for UVB (0.297 μm peak) and 1 for photosynthetically active radiation (PAR). Measurements focused on inside-forest shade conditions at sites 0 to ca 15 km from the Black Sea and at altitudes up to ca 120 m above sea level. Some of the sites were also studied using a high-resolution spectroradiometer. A sequential measuring strategy was necessary. This involves potentially large uncertainties, here addressed through estimations of the variability around the sinusoidal course of daylight. Light-quality regimes were found to be in general support of earlier studies of deciduous forests. Our data from the broad-band sensors and from the spectroradiometer are mutually supportive. They indicate a stronger red-shift below Q.f. canopies than below canopies in enclaves dominated by Fagus orientalis and Pinus sylvestris. Transmission in the range 0.50–0.55 μm increases beneath the three types of canopies, most pronounced in the Q.f. case. Analysis of relationships between the inside-forest to open-field irradiance ratio and LAI supports the use of Beer’s Law. We found a fairly strong relationship between the red (0.66 μm) to far-red (0.73 μm) irradiance ratios (R/FR) and LAI for the Q.f. forest. In quantitative terms, the result is new for this Q.f. region, and suggests further research to explore whether a two-sensor approach (0.66 and 0.73 μm) might offer possibilities for further low-cost mapping of the spatio-temporal patterns of R/FR and LAI in Strandzha. Such mapping would assist in further studies of the region’s forest biogeochemistry and vitality.     

1991-2017年叶尔羌河流域冰川景观格局时空演变

冰川景观变化是全球环境和气候变化的共同"指示器"。随着全球气候变化加剧，干旱和半干旱地区的冰川景观将进一步变化。科学评估冰川景观格局时空演变特征，为应对冰川景观变化及其影响提供科学参考。基于1991-2017年Landsat TM/ETM+/OLI遥感影像，采用监督分类方法获取叶尔羌河流域冰川景观时空格局及变化数据，利用景观格局指数、质心迁移模型、分形维数等方法分析近26年叶尔羌河流域冰川景观格局时空演变特征。结果表明：（1）1991-2017年叶尔羌河流域冰川斑块面积呈消减趋势，但有所减缓，共减少799.50 km²（-13.09%）。冰川斑块面积消减主要集中在海拔5400-5800 m之间，相较之下，海拔4400 m以下的区域冰川斑块面积消减率最高，达63.68%；不同坡度冰川景观消减率存在差异，陡坡冰川斑块面积消减率最高（15.98%），急陡坡消减率最低（2.87%）；阴阳两坡冰川景观均呈消减趋势，阳坡冰川斑块面积消减速率显著高于阴坡。（2）近26年来，叶尔羌河流域冰川斑块数量、最大斑块指数均减小，而平均形状指数、平均周长面积比、分裂指数均增加，表明冰川景观不断消减，破碎化程度增加。（3）研究期间，叶尔羌河流域冰川景观质心发生迁移，整体呈现东北偏移趋势。（4）通过分形理论对叶尔羌河流域冰川景观空间结构特征进行分析表明，该流域冰川景观消减率略微降低，但仍然处于持续消融状态。