Does famine influence sex ratio at birth? Evidence from the 1959–1961 Great Leap Forward Famine in China

The current study examined the long-term trend in sex ratio at birth between 1929 and 1982 using retrospective birth histories of 310 101 Chinese women collected in a large, nationally representative sample survey in 1982. The study identified an abrupt decline in sex ratio at birth between April 1960, over a year after the Great Leap Forward Famine began, and October 1963, approximately 2 years after the famine ended, followed by a compensatory rise between October 1963 and July 1965. These findings support the adaptive sex ratio adjustment hypothesis that mothers in good condition are more likely to give birth to sons, whereas mothers in poor condition are more likely to give birth to daughters. In addition, these findings help explain the lack of consistent evidence reported by earlier studies based on the 1944-1945 Dutch Hunger Winter or the 1942 Leningrad Siege.     

Effects of sow nutrition during gestation on within-litter birth weight variation: a review

The increasing demand for efficiency in pork production requires great specialization of all sectors involved in this activity. In this context, the development of strategies that could reduce undesirable traits related with negative effects on piglet survival and postnatal growth and development are essential for the pig industry. Currently, special attention is given to variation in birth weight, as some evidences suggest an increased within-litter birth weight variation in modern sows. This variation has been shown to be associated with preweaning mortality, variable weights at weaning and deteriorated growth performance, which results in economic losses and lower efficiency. Therefore, understanding the factors that can influence the events that occur during gestation and that have an impact on the fetal growth and development are important to achieve better efficiency and also to develop strategies that can be used to achieve increased within-litter uniformity of piglet birth weight. This study concludes that even at a given placental size, fetal growth may vary because of differences in placental vascularization and efficiency. Feeding extra feed or energy during late gestation only marginally improves birth weight, and positive effects are not consistent between different studies. The detrimental effects of protein restriction on fetal growth during early gestation may be due to altered placental and endometrial angiogenesis and growth, which leads to a reduction in placental-fetal blood flow, nutrient supply from mother to the fetuses and ultimately to fetal growth retardation. The number of studies that attempted to influence within-litter birth weight variation by means of sow nutrition during gestation is limited. Therefore, more research concerning sow nutrition during gestation associated with the provision of balanced diets to meet requirements of the sows and fetuses are still required. This knowledge may subsequently provide starting points for the design of nutritional strategies that can influence within-litter birth variation.     

Plant bioreactors - the taste of sweet success

Thaumatins are intensely sweet proteins (3000 times sweeter than the same weight of sucrose) that are found in the arils of the tropical perennial plant Thaumatococcus daniellii Benth and are produced commercially by aqueous extraction from the fruits. The proteins are widely used as sweeteners and flavor enhancers in the food industry, and the European Food Safety Association (EFSA) has recently confirmed that their use as feed additive (1 to 5 mg/kg complete feed) is safe for all animal species. Given the large market for sweeteners and flavor enhancers, thaumatins could become increasingly important in the food and feed additives sector. In this issue of Biotechnology Journal, a study examines the production of thaumatin in tobacco hairy root cultures.     

Plantlet recruitment is the key demographic transition in invasion by Kalanchoe daigremontiana

Biological invasions have a great impact on biodiversity and ecosystem functioning worldwide. Kalanchoe daigremontiana is a noxious invasive plant in arid zones. Besides being toxic for domestic animals and wildlife, this species inhibits the growth of native plants. Its rapid proliferation in Cerro Saroche National Park (Venezuela) is of great concern because this area hosts several species endemic to the scarce arid zones in the Caribbean. The traits of K. daigremontiana that contribute to its invasive success are unknown. Based on empirical data, we derived a stage structured, stochastic and density-dependent model, to identify characteristics relevant for its establishment. Sensitivity analyses revealed that the establishment of K. daigremontiana depends exclusively on plantlet recruitment. Because asexual plantlets reproduce in less than 1 year populations are able to increase rapidly during the initial phases of invasion, when extinction risks are higher. Sexual seedlings, on the contrary, require a minimum of 3 years to reproduce. As a result, seedling recruitment contributes little to the transient dynamics of the population and therefore cannot warrant the successful establishment of the species. Simulations of various management strategies show that eradication through plant removal may only be achieved if harvest begins shortly after introduction. If a rapid response is not possible, reducing the survival and growth rates of plantlets through biological control is an alternative option. Thus, a strict control of dispersal of plantlets by humans and a continuous monitoring of new invasions should be the first priority for reducing further impact on native species.     

Effect of nitrogen,phosphorus and potassium availability on emergence,nodulation and growth of acidicole Trifolium arvense L. in alkaline soil

The acidicole behavior of many species is given by their inability to acquire enough P in alkaline soil, but reasons for acidicole (syn. calcifuge) behavior of Trifolium arvense have never been studied experimentally. We asked how emergence of seedlings, the survival of plants, the growth of aboveground organs, the nodulation and the growth of roots of this species is affected by different N, P and K supply in alkaline soil. In the years 2010 and 2011, we performed a pot experiment (ten N, P and K fertilizer treatments) with seeding of T. arvense into alkaline soil. The acidicole behavior of T. arvense proved to be connected with the inability of seedlings to acquire enough P during their emergence. In all treatments, T. arvense was not able to flower in the seeding year and in the second year it flowered only in P treatments. This indicates the biennial character of the species in the case of late seeding and points to a strong P limitation of flowering and seeds production in plants grown on alkaline soil. Without P addition, T. arvense was not able to develop beyond the seedling stage. Nodulation was positively affected by P application and negatively by N application. Although T. arvense is a typical species for P poor soils, it does not suffer from P toxicity under high P supply. We concluded that the acidicole behavior of T. arvense is based on its P limitation when growing on alkaline soil.     

Cooperative vigilance: the guanaco's (Lama guanicoe) key antipredator mechanism

The concept of sociality has been associated with the effectiveness of antipredator mechanisms, like cooperative vigilance and the dilution effect. Lama guanicoe (guanaco) is a social native herbivore in South America and a social species. The objectives of this study were to evaluate the antipredator responses of different-sized groups of guanacos in areas with varying predation risks and to determine antipredator mechanisms in guanacos. For this, we measured different antipredator responses to a potential predator (human subjects). Detection of predator and flight distances from predator both increased with a greater number of guanacos per group and with greater distances among guanacos within the social group. Both buffer distance and flight time decreased with a greater number of guanacos per group, but increased with greater distances among guanacos inside the social group. Solitary adult males moved shorter distance and mixed groups moved greater distances. Flight distances were greater in areas with tall and dense vegetation than in areas with low vegetation. Buffer distance and flight time were shorter in undulating land than on flat lands, and groups were usually observed on hill slopes. Our results suggest that the benefit of social grouping in guanacos is the increased probability of avoiding predator with cooperative vigilance and not with the dilution effect. This means that a predator could be detected earlier when approaching a guanaco group than when approaching a solitary individuals and could thus be avoided.     

A randomized trial of genetic information for personalized nutrition

Personal genetic information has become increasingly accessible to the public as a result of direct-to-consumer (DTC) genetic tests; however, concerns have been raised over their value and potential risks. We compared the effects of providing genotype-based dietary advice with general recommendations on behavioral outcomes using a randomized controlled study. Participants were men and women from the Toronto Nutrigenomics and Health Study between the ages of 20–35 years (n = 149) who completed a survey to assess their awareness of DTC genetic tests and nutrigenomics, as well as potential motivations for undergoing genetic testing. Participants were then randomized into an intervention (I) or control (C) group and were given either genotype-based personalized dietary advice or general dietary advice, respectively. A second survey was administered to assess the participants’ opinions of the dietary reports they received. A greater proportion of participants in the intervention group agreed that they understood the dietary advice they were given (93% (I) vs. 78% (C); p = 0.009). Participants in the intervention group were more likely to agree that the dietary recommendations they received would be useful when considering their diet (88% (I) vs. 72% (C); p = 0.02) and wanted to know more about the recommendations (95% (I) vs. 76% (C); p < 0.0001). Only 9% of participants in the intervention group reported feeling uneasy about learning their genetic information. These findings suggest that individuals find dietary recommendations based on genetics more understandable and more useful than general dietary advice. Very few feel uneasy about receiving their genetic information that relates to personalized nutrition.     

Species concepts and floras: what are species for?

In 1992, in a special paper in the American Journal of Botany, Ernst Mayr attempted to ‘prove’ the biological species concept (BSC) worked as well in plants as it did in animals by analyzing the flora of the Concord region of northern Massachusetts. He concluded that there were minimal difficulties when applying the BSC for the plants of this particular area, and concluded that botanists were misguided in not accepting the BSC. He suggested that what he called ‘typological’ thinking was prevalent in the taxonomic community, and that this was a factor in botanical resistance to the BSC. Typology, as defined by Mayr in his 1992 foray into botany, is to a certain extent a straw‐man and, by the late 20th Century, no longer a way of thinking in widespread use in the taxonomic community in any organismal group. Here, I examine his analysis in the light of current interest in plant diversity. Species can be characterized as hypotheses about the distribution of variation in nature, subject to test with new data of many kinds. Species concepts like the BSC, although of interest philosophically and to researchers looking at mechanisms of speciation, may actually get in the way of achieving a baseline understanding of the diversity of life on Earth. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95 , 17–25.