On construction of optimal mixed-level supersaturated designs

Supersaturated design (SSD) has received much recent interest because of its potential in factor screening experiments. In this paper, we provide equivalent conditions for two columns to be fully aliased and consequently propose methods for constructing $E(f_{\mathrm{NOD}})$- and $\chi^2$-optimal mixed-level SSDs without fully aliased columns, via equidistant designs and difference matrices. The methods can be easily performed and many new optimal mixed-level SSDs have been obtained. Furthermore, it is proved that the nonorthogonality between columns of the resulting design is well controlled by the source designs. A rather complete list of newly generated optimal mixed-level SSDs are tabulated for practical use.Comment: Published in at http://dx.doi.org/10.1214/11-AOS877 the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

Do Bird Assemblages Predict Susceptibility by E-Waste Pollution? A Comparative Study Based on Species- and Guild-Dependent Responses in China Agroecosystems

Indirect effects of electronic waste (e-waste) have been proposed as a causal factor in the decline of bird populations, but analyses of the severity impacts on community assembly are currently lacking. To explore how population abundance/species diversity are influenced, and which functional traits are important in determining e-waste susceptibility, here we surveyed breeding and overwintering birds with a hierarchically nested sampling design, and used linear mixed models to analyze changes in bird assemblages along an exposure gradient in South China. Total bird abundance and species diversity decreased with e-waste severity (exposed < surrounding < reference), reflecting the decreasing discharge and consequent side effects. Twenty-five breeding species exclusively used natural farmland, and nine species decreased significantly in relative abundance at e-waste polluted sites. A high pairwise similarity between exposed and surrounding sites indicates a diffuse effect of pollutants on the species assembly at local scale. We show that sensitivity to e-waste severity varies substantially across functional guild, with the prevalence of woodland insectivorous and grassland specialists declining, while some open farmland generalists such as arboreal frugivores, and terrestrial granivores were also rare. By contrast, the response of waterbirds, omnivorous and non-breeding visitors seem to be tolerable to a wide range of pollution so far. These findings underscore that improper e-waste dismantling results in a severe decline of bird diversity, and the different bird assemblages on polluted and natural farmlands imply species- and guild-dependent susceptibility with functional traits. Moreover, a better understanding of the impact of e-waste with different pollution levels, combined multiple pollutants, and in a food-web context on bird is required in future

Lineage diversification and historical demography of a montane bird Garrulax elliotii - implications for the Pleistocene evolutionary history of the eastern Himalayas

<p>Abstract</p> <p>Background</p> <p>Pleistocene climate fluctuations have shaped the patterns of genetic diversity observed in many extant species. In montane habitats, species' ranges may have expanded and contracted along an altitudinal gradient in response to environmental fluctuations leading to alternating periods of genetic isolation and connectivity. Because species' responses to climate change are influenced by interactions between species-specific characteristics and local topography, diversification pattern differs between species and locations. The eastern Himalayas is one of the world's most prominent mountain ranges. Its complex topography and environmental heterogeneity present an ideal system in which to study how climatic changes during Pleistocene have influenced species distributions, genetic diversification, and demography. The Elliot's laughing thrush (<it>Garrulax elliotii</it>) is largely restricted to high-elevation shrublands in eastern Himalayas. We used mitochondrial DNA and microsatellites to investigate how genetic diversity in this species was affected by Pleistocene glaciations.</p> <p>Results</p> <p>Mitochondrial data detected two partially sympatric north-eastern and southern lineages. Microsatellite data, however, identified three distinct lineages congruent with the geographically separated southern, northern and eastern eco-subregions of the eastern Himalayas. Geographic breaks occur in steep mountains and deep valleys of the Kangding-Muli-Baoxin Divide. Divergence time estimates and coalescent simulations indicate that lineage diversification occurred on two different geographic and temporal scales; recent divergence, associated with geographic isolation into individual subregions, and historical divergence, associated with displacement into multiple refugia. Despite long-term isolation, genetic admixture among these subregional populations was observed, indicating historic periods of connectivity. The demographic history of <it>Garrulax elliotii </it>shows continuous population growth since late Pleistocene (about 0.125 mya).</p> <p>Conclusion</p> <p>While altitude-associated isolation is typical of many species in other montane regions, our results suggest that eco-subregions in the eastern Himalayas exhibiting island-like characteristics appear to have determined the diversification of <it>Garrulax elliotii</it>. During the Pleistocene, these populations became isolated on subregions during interglacial periods but were connected when these expanded to low altitude during cooler periods. The resultant genetic admixture of lineages might obscure pattern of genetic variation. Our results provide new insights into sky island diversification in a previously unstudied region, and further demonstrate that Pleistocene climatic changes can have profound effects on lineage diversification and demography in montane species.</p

Connections between uniformity and aberration in general multi-level factorials

Discrepancy, Generalized minimum aberration, Generalized wordlength pattern, Indicator function, Uniformity,

A newly formed hexaploid wheat exhibits immediate higher tolerance to nitrogen-deficiency than its parental lines

Abstract Background It is known that hexaploid common wheat (Triticum aestivum L.) has stronger adaptability to many stressful environments than its tetraploid wheat progenitor. However, the physiological basis and evolutionary course to acquire these enhanced adaptabilities by common wheat remain understudied. Here, we aimed to investigate whether and by what means tolerance to low-nitrogen manifested by common wheat may emerge immediately following allohexaploidization. Results We compared traits related to nitrogen (N) metabolism in a synthetic allohexaploid wheat (neo-6×, BBAADD) mimicking natural common wheat, together with its tetraploid (BBAA, 4×) and diploid (DD, 2×) parents. We found that, under low nitrogen condition, neo-6× maintained largely normal photosynthesis, higher shoot N accumulation, and better N assimilation than its 4× and 2× parents. We showed that multiple mechanisms underlie the enhanced tolerance to N-deficiency in neo-6×. At morphological level, neo-6× has higher root/shoot ratio of biomass than its parents, which might be an adaptive growth strategy as more roots feed less shoots with N, thereby enabling higher N accumulation in the shoots. At electrophysiological level, H+ efflux in neo-6× is higher than in its 4× parent. A stronger H+ efflux may enable a higher N uptake capacity of neo-6×. At gene expression level, neo-6× displayed markedly higher expression levels of critical genes involved in N uptake than both of its 4× and 2× parents. Conclusions This study documents that allohexaploid wheat can attain immediate higher tolerance to N-deficiency compared with both of its 4× and 2× parents, and which was accomplished via multiple mechanisms