Breakfast eating and overweight in a pre-school population: is there a link?

OBJECTIVES: To analyse the socio-economic factors related to breakfast eating, the association between breakfast eating and overweight, and to gain a more thorough understanding of the relationship between these two elements in a population-based cohort of 4.5-year-old children. We hypothesised that a relationship could be observed between breakfast skipping and overweight independently of socio-economic factors such as ethnicity, maternal education, single parenting and family income. DESIGN: A population-based study whereby standardised nutritional interviews were conducted with each child's parent. The children's height and weight were taken by a trained nutritionist and parents were asked about their child's breakfast eating. SETTING: The analyses were performed using data from the Québec Longitudinal Study of Child Development (1998-2002), conducted by Santé Québec (Canada). SUBJECTS: Subjects were 1549 children between the ages of 44 and 56 months, with a mean age of 49 months. RESULTS: Almost a tenth (9.8%) of the children did not eat breakfast every day. A greater proportion of children with immigrant mothers (19.4% vs. 8.3% from non-immigrant mothers), with mothers with no high school diploma (17.5% vs. <10% for higher educated mothers) and from low-income families (15% for income of $39,999 or less vs. 5-10% for better income) did not eat breakfast every day. Not eating breakfast every day nearly doubled the odds (odds ratio=1.9, 95% confidence interval 1.2-3.2) of being overweight at 4.5 years when mother's immigrant status, household income and number of overweight/obese parents were part of the analysis. CONCLUSION: Although our results require replication before public policy changes can be advocated, encouraging breakfast consumption among pre-school children is probably warranted and targeting families of low socio-economic status could potentially help in the prevention of childhood obesity.     

Land-cover change and human population trends in the greater Serengeti ecosystem from 1984–2003

The growth of human populations around protected areas accelerates land conversion and isolation, negatively impacting biodiversity and ecosystem function, and can be exacerbated by immigration. It is often assumed that immigration around protected areas is driven by attraction in the form of economic benefits, but in many cases, people may be pushed from their areas of origin toward protected areas. Mitigating the effects of immigration around protected areas necessitates understanding the actual mechanisms causing it, which can be aided by analysis of patterns of land-cover change. Our goal was to identify the reasons for human population growth and land-cover change around the protected areas in the greater Serengeti ecosystem (henceforth “the park”), and to relate agricultural conversion from 1984–2003 to trends in human demography. We found that conversion of natural habitats to agriculture was greatest closer to the park (up to 2.3% per year), coinciding with the highest rates of human population growth (3.5% per year). Agricultural conversion and population growth were greatest where there was less existing agriculture, and population density was lowest. Lack of unfarmed land farther from the park, coupled with greater poverty near the park, suggest that movement away from areas with high population densities and land scarcity was likely driving immigration near the park, where arable land was available. Our results are essential for conservation planning for one of Africa’s hallmark ecosystems, and should encourage further examination of population growth and land-cover trends near protected areas throughout the developing world.     

Sampling design and its effect on population monitoring: How much monitoring do turtles really need?

Marine turtles are a taxon of world-wide conservation concern. Effective long-term monitoring is hampered by the fact that populations are widely dispersed except during the breeding season. Thus most monitoring programmes focus on nesting beaches, necessitating resource intensive studies, often over months, that could conceivably, be less comprehensive and focus on more parsimonious sampling. We analyse 11 years of exhaustive monitoring data for two species of Mediterranean marine turtles (Chelonia mydas and Caretta caretta). We resample using a variety of plausible sub-sampling regimens to estimate the total annual nesting population. We project our dataset into the future applying a range of population change rates to explore how adopting a monitoring programme based on sub-sampling would, for example, affect our ability to detect population decline. We show that accurate annual population estimates can be achieved with as few as 14 days of survey effort providing monitoring spans the peak of nesting. Furthermore, the modelled impact of sampling-based monitoring suggests that the duration to detect population change is not increased greatly. Our findings have implications for all marine turtle monitoring and have applicability to other animal groups. It is often considered desirable to perform exhaustive monitoring, with aversion of basing policy recommendations on partial data. However, comprehensive long-term monitoring programmes, particularly in developing nations, although presenting a number of advantages, are often impossible. Accurate total annual censuses can be achieved through a variety of sub-sampling regimens without sacrificing the ability to detect changes in the population trends over time. In this example, a solid block of at least 3 weeks sampling that encompasses the peak of the nesting season is advised.     

Do epiphytic orchids behave as metapopulations? Evidence from colonization, extinction rates and asynchronous population dynamics

Previous in situ studies of orchid population dynamics with conservation relevance have focused on one or a few populations in a limited area. Many species of orchids occur as hyperdispersed populations in ephemeral habitats (epiphytic, twig epiphytes, short lived or vulnerable host). In this contribution, we show that orchid populations that are patchily distributed and that exist in disturbance-prone environments may act somewhat like a metapopulation with high turnover and low correlation in population dynamics. We tested for evidence of metapopulation dynamics in the riparian orchid Lepanthes rupestris by sampling over 1000 sites (250 initially occupied, 750 initially unoccupied) in biannual surveys for 5 years. Extinction and colonization of groups of orchids on a single substrate or patch (either trees or boulders) was common and more or less consistent across different time periods, and asynchronous subpopulation dynamics were evident among the populations. From this we predict non-zero equilibrium values for site occupancy () of L. rupestris. Nevertheless, this study species differed from a typical Levins’ metapopulation system in that small populations were more likely to go extinct than large populations, and that colonization of previously occupied sites was more common than colonization of initially unoccupied sites suggesting that site quality may influence population persistence and colonization. A major difficulty applying the metapopulation approach to orchid conservation is identifying empty sites suitable for colonization. In spite of this limitation, our study highlights the necessity of following multiple orchid subpopulations (e.g., an entire orchid “metapopulation” in the broad sense) may provide a more accurate basis for predicting persistence in epiphytic orchids.     

Effect of herbicide used with years (8 + 1) on soil enzymic activity and microbial population diversity

Purpose

Soil microbes play important roles in plant nutrition and soil conservation, and the diversity and population of soil microbe are influenced by abiotic and biotic factors associated with different soil managements. However, the information concerning soil microbe diversity and population structure and its relation with soil fertility and enzyme activities are scarce in crop rotation under different soil management system.

Materials and methods

This paper reports the effects of three weeding managements (herbicide (2-chloro-N-(ethoxymethyl)-N-(2-ethyl-6-methylphenyl) acetomide, C1₄H₂₀ClNO₂), manual weeding, and no weeding (CK)), on soil microbial diversity, population structure, and its relationship with soil active organic matter (AOM) and pH, and the activity of soil enzymes like sucrase, catalase, and urease activities from long-term test area in red soil upland field in southeast China, which was set up since 2006. Soil samples at 0–20-cm depths were collected before (8 years) and after (8 + 1 years) weeding management in April 2014.

Results and discussion

Soil enzymes (sucrase, catalase, and urease activity) and soil microbial populations had no significant difference (P > 0.05) under the three weeding treatments. Based on richness of microbial population up to 0.10%, the phyla Proteobacteria and Actinobacteria highly dominated the three soil treatments, averagely accounting for 21.76 and 21.44%. Chloroflexi was the next phylum, about accounting for 6.84%. Firmicutes, Verrucomicrobia, and Planctomycetes phylum accounted for 4.98, 4.78, and 4.23%, respectively. The percentage of Gemmatimonadetes was 2.76%, and that of Bacteroidetes was about 1.45%. Armatimonade and Nitrospira were the lowest, with 0.69 and 0.26%, respectively. Among the 20 phyla, only 5 had significant correlation with some of the soil properties. Twenty-one in 46 classes had significant correlation with some of the soil properties. Armatimonadetes and Fusobacteria had positive correlation with moisture. Acidobacteria_Gp3, Deltaproteobacteria, Chthonomonadetes, Armatimonadetes_gp4, and Euryarchaeota also were positively correlated with moisture. Negative correlation between Armatimonadetes, Chloroflexi, Chthonomonadetes, and Armatimonadetes_gp5 and AOM exists, and Armatimonadetes, Chthonomonadetes, Clostridia, Armatimonadetes, and pH were negatively correlated. Fusobacteria was positively correlated with catalase. Acidobacteria_Gp10 and Armatimonadia were positively correlated with catalase. Chthonomonadetes, Clostridia, and Armatimonadetes_gp5 were correlated with urease. Gammaproteobacteria and Flavobacteria were correlated with sucrase.

Conclusions

For long-term herbicide experiment conducted on the Dongxiang upland site, no significant effect of herbicide on soil microbial community composition and enzyme activities was found. Further work is needed to relate microbial community structure and function in different herbicide systems or season sampling, even to detect herbicide effect on community structure during the growing season.

     

Effects of a tropical cyclone on littoral and sub-littoral biotic communities and on a population of Dugongs (Dugong dugon (Müller))

The extensive damage to littoral and sub-littoral biotic communities caused by cyclone ‘Althea’, which crossed the tropical coast of Queensland on 24 December, 1971, are described. The effects of high wind speeds (mean 129·7 km/h), turbulent seas, storm surges, and heavy rainfall on mangrove, sea grass, algal, and coral reef communities are discussed. Mangroves withstood the immediate effects of the cyclone and protected coastal areas. However, long-term effects on mangroves are apparent. Severe wave action, shifting sand, and low salinities caused extensive damage to sea grass, algal, and coral reef communities. The effects of the cyclone on a Dugong population are described. The catches of Dugongs in shark nets set off Townsville increased from an average of 12·7 per year before the cyclone to 41 in 1972 (the year following the cyclone). This increase is attributed to increased movements in search of food, following extensive damage to sea grass beds. Associated with increased movements, there occurred a change in diet whereby large amounts of brown algae were eaten in addition to sea grasses. Sex and size (age) distributions of captured Dugongs are given and their possible significance discussed.     

Does the diet of the Balearic population, a Mediterranean-type diet, ensure compliance with nutritional objectives for the Spanish population?

OBJECTIVES: To assess the dietary habits of Balearic Islands' consumers who are successful in meeting current nutritional recommendations, to find clues for the development of future food-based dietary guidelines (FBDG) that would be relevant to this population. DESIGN: Cross-sectional nutritional survey carried out in the Balearic Islands between 1999 and 2000. SUBJECTS AND METHODS: Dietary habits were assessed by means of 24-hour recall (two non-consecutive days: warm and cold season) and a food-frequency questionnaire in a random sample (n=1200, aged 16-65 years) living in private households. Differences in percentage of compliers with the intermediate nutritional objectives for the Spanish population and differences in food consumption patterns between genders and between high (above the upper quartile of intake) and low (below the lower quartile of intake) consumers of fat, saturated fatty acids (SFA), fibre, and fruit and vegetables were analysed. RESULTS: Gender differences were observed in nutrient and energy intakes, as well as in attainment of the recommendations. Less than 25% of the population reached the intermediate nutritional recommendations for iodine, fruit, carbohydrates, SFA, fibre and vegetables. Low fat/SFA and high fruit and vegetables/fibre consumers kept a diet in line with the traditional Balearic diet and prevailing dietary pyramids, which ensured better compliance with the nutritional goals. CONCLUSIONS: The intermediate nutritional objectives for the Spanish population could be achieved through maintenance of the traditional Balearic diet, a Mediterranean-type diet in the Balearic population. Therefore, this dietary model could be used to develop FBDG relevant to this population.     

Relative fitness of wild and captive-reared piping plovers: Does egg salvage contribute to recovery of the endangered Great Lakes population?

Since 1992, efforts to recover the US federally endangered Great Lakes piping plover (Charadrius melodus) have included population supplementation with captive-reared young raised from abandoned eggs. Using banding data collected 1993-2008 and Cormack-Jolly-Seber models in program MARK we estimated resighting rates (ρ) and apparent survival (Φ) of first-year (1) and after-first-year (2+) plovers. Reproductive success was measured by estimating mean number of eggs laid, chicks hatched and chicks fledged per wild-reared or captive-reared parent, and these values were compared with a permutation test. The best-supported mark-resighting model indicated wild-reared plovers had higher Φ₁ and Φ₂₊ than captive-reared plovers. Breeding propensity influenced detection of wild plovers, whereas unique band combinations facilitated detection of yearling captive-reared plovers. Captive-reared (n = 10) and wild-reared (n = 57) plovers laid similar numbers of eggs, but wild-reared plovers hatched 36% more chicks and fledged 56% more young. Reproductive values derived from matrix models suggest captive-reared piping plovers are less fit than similarly aged wild-reared birds upon release and demonstrate reduced fitness in subsequent years. The Great Lakes captive-rearing effort has successfully produced a minimum of 10 breeding adults from 192 eggs that otherwise would have had no reproductive value; these captive-reared individuals now constitute up to 3% of the total population. Small scale salvage and captive-rearing of abandoned eggs should be considered as a technique to supplement existing recovery efforts in highly imperiled populations.     

Self-generated microbial population or cultured microflora – an important criterion toward development of an effective and economically viable road map for organic soil management

Huge depletion of soil microflora under conventional farming practice has become the primary contributory factor toward the present depletion of soil and crop productivity. Reconstitution of soil microbial dynamics has been identified as the only way out, but there has been a debate regarding the most effective pathway for soil rejuvenation i.e. whether to create the environment for natural proliferation or opt for inoculation of laboratory generated microbes. In this respect, a study was undertaken at Maud T.E. (Assam) under FAO-CFC-TBI Project, where bio-fertilizer (microbial inoculant, MI), vermicompost (organic food source, OF), vermicompost + bio-fertilizer (OF+MI), and Novcom compost (representing self-generated native microflora in the order of 10¹⁶c.f.u. along with organic food source, SNM); were taken as treatments for a yield target of 1500 kg made tea/ha. The highest crop yield (1500 kg ha^?1) along with high and consistent soil quality development was noted under SNM treatment; while MI influenced lowest yield (1268 kg ha^?1) and minimal soil response. Addition of the organic food source with cultured microbes (MI+OF) was found to improve crop performance (1427 kg ha^?1), but with 7.60 times higher cost (Rs. 39.97 kg^?1 made tea). Economic viability study indicated that except SNM, all other treatments were vulnerable toward crop loss or market downfall.     

Secular and socio-economic trends in compliance with dietary targets in the north Glasgow MONICA population surveys 1986-1995: did social gradients widen?

OBJECTIVE: To compare trends in the consumption of key foods over 10 years in the most deprived and least deprived quarters in north Glasgow, Scotland as defined by the Carstairs deprivation index for their postcode of domicile. DESIGN: Four random, cross-sectional, age- and gender-stratified population surveys carried out in 1986, 1989, 1992 and 1995. After assigning a deprivation score, food-frequency questionnaires from 2883 men and 3127 women were examined for compliance with dietary targets, examining trends by gender and within the most and least deprived quarters of the population. SETTING: North Glasgow, Scotland. SUBJECTS: Over 600 men and 600 women (aged 25-64 years) in each of the four survey years who completed a lifestyle questionnaire including a food frequency section. RESULTS: Increasing trends in the reported consumption of fruit and vegetables and oil-rich fish were observed over the 10-year period. However, the trend to increased fruit and vegetable consumption in the most deprived groups was not significant, and in 1995 only 8% of men and 12% of women in this group claimed consumption of these foods 4 or more times a day. In general, a higher percentage of those in the least deprived group met the targets for the key foods. CONCLUSIONS: Trends to increasing consumption of fruit and vegetables and fish were in the right direction, but the targets for consumption of certain key foods were met by a minority of the population. The progress towards the target for fruit and vegetables showed widening social gradients with time.     

Can natural disturbance-based forestry rescue a declining population of grizzly bears?

Forest managers are increasingly considering historic patterns of natural forest disturbance as a model for forest harvesting and as a coarse-filter ecosystem management tool. We evaluated the long-term (100-year) persistence of a grizzly bear population in Alberta, Canada using forest simulations and habitat modelling. Even with harvesting the same volume of timber, natural disturbance-based forestry resulted in a larger human footprint than traditional two-pass forestry with road densities reaching 1.39 km/km² or more than three times baseline conditions and suggested maximum levels of security for grizzly bears. Because bears favour young forests and edges where food resources are plentiful, a future shift to young forests and more edge habitat resulted in a 20% projected increase in habitat quality and a 10% projected increase in potential carrying capacity. Human-caused mortality risk, however, offset any projected gains in habitat and carrying capacity resulting in the loss of all secure, unprotected territories, regardless of forest harvest method, within the first 20-30 years of simulation. We suggest that natural disturbance-based forestry is an ill-suited management tool for sustaining declining populations of grizzly bears. A management model that explicitly considers road access is more likely to improve grizzly bear population persistence than changing the size of clear-cuts. In fact, large clear cuts might be counter productive for bears since a diversity of habitats within each bear’s home range is more likely to buffer against future uncertainties.     

Do species life history traits explain population responses to roads? A meta-analysis

Efforts to mitigate road effects are now common in new highway construction projects. For effective mitigation of road effects it is important to identify the species whose populations are reduced by roads, so that mitigation efforts can be tailored to those species. We conducted a meta-analysis using data from 75 studies that quantified the relationship between roads and/or traffic and population abundance of at least one species to determine species life history characteristics and behavioral responses to roads and/or traffic that make species or species groups prone to negative road and/or traffic effects. We found that larger mammal species with lower reproductive rates, and greater mobilities, were more susceptible to negative road effects. In addition, more mobile birds were more susceptible to negative road and/or traffic effects than less mobile birds. Amphibians and reptiles were generally vulnerable to negative road effects, and anurans (frogs and toads) with lower reproductive rates, smaller body sizes, and younger ages at sexual maturity were more negatively affected by roads and/or traffic. Species that either do not avoid roads or are disturbed by traffic were more vulnerable to negative population-level effects of roads than species that avoid roads and are not disturbed by traffic. In general, our results imply that priority for mitigation should be directed towards wide-ranging large mammals with low reproductive rates, birds with larger territories, all amphibians and reptiles, and species that do not avoid roads or are disturbed by traffic.     

Genetic diversity and population structure in a regional collection of Kersting’s groundnut (Macrotyloma geocarpum (Harms) Maréchal & Baudet)

Genetic Resources and Crop Evolution - Kersting’s groundnut (Macrotyloma geocarpum (Harms) Maréchal &amp; Baudet) is an important source of protein and essential nutrients that...     

First insight into genetic diversity and population structure of the Caucasian wild apple (<Emphasis Type="Italic">Malus orientalis</Emphasis> Uglitzk.) in the Hyrcanian forest (Iran) and its resistance to apple scab and powdery mildew

Investigating population genetic structure and diversity, and resistance to pathogens in crop wild relatives are key steps to assess appropriate conservation and breeding programs. The Caucasian wild apple (Malus orientalis Uglitzk.) is an emblematic fruit tree of the Hyrcanian forest and is supposed to be a contributor to the cultivated apple genome (Malus domestica Borkh. Yet, no study has investigated its population structure, diversity and susceptibility to the two main pathogens of apples, the apple scab (Venturia inaqualis) and the powdery mildew (Podosphaera leucotricha). Here, we investigated population genetic structure and diversity of M. orientalis in the Hyrcanian forest as a mean to identifying future targeted populations for apple conservation and breeding programs. We genotyped using multilocus microsatellite 100 M. orientalis trees sampled in 14 sites. These trees were also screened for presence/absence of six (Rvi6, Vr, Rvi4, Rvi15, Rvi5 and Rvi11) and three (Pl-1, Pl-w, Pl-d) resistance genes to the apple scab and the powdery mildew respectively. Our results showed significant but weak between-site genetic differentiation and isolation by distance pattern suggesting substantial historical gene flow for M. orientalis in this area. We also detected a West-Eastern genetic structure across the Hyrcanian forest with five main populations showing admixture. We also showed a high diversity of resistance genes to apple scab across sites; in contrast, we only found one resistance gene to powdery mildew. These results are a first glimpse to settle wild apple conservation programs in Iran and pinpoint Iranian wild apple populations as an untapped source for apple breeding.     

How reliable are amphibian population metrics? A response to Kroll et al.

Kroll et al. [Kroll, A.J., Runge, J.P., MacCracken, J.G., 2009. Unreliable amphibian population metrics may obfuscate more than they reveal. Biological Conservation] criticized our recent advocacy for combining readily attainable metrics of population status to gain insight about relationships between terrestrial plethodontid salamanders and forest succession [Welsh, Jr., H.H., Pope, K.L., Wheeler, C.A., 2008. Using multiple metrics to assess the effects of forest succession on population status: a comparative study of two terrestrial salamanders in the US Pacific Northwest. Biological Conservation 141, 1149–1160]. They argue that each of our metrics has the potential to be biased or flawed and, therefore, any inferences so derived are likely to be uncertain and misleading. One of our main goals was to highlight the value of combining multiple quantitative approaches with logic, knowledge of species’ biology and parsimony when interpreting findings, as a means to counter uncertainty that might occur with any single metric. We applied a sampling design that minimizes the chance of bias in detections and counts, included multiple statistical methods to test relationships, and incorporated past research and species’ biology when interpreting findings. We disagree with Kroll et al. [Kroll, A.J., Runge, J.P., MacCracken, J.G., 2009. Unreliable amphibian population metrics may obfuscate more than they reveal. Biological Conservation] that the potential biases associated with the individual metrics mean that the inferences from the study are too uncertain to be useful by managers. We examined metrics that are more informative than simple site occupancy, including relative abundance, life stage distributions, and body condition, to inform our knowledge of population status. Combining metrics allows us to use readily attainable data to yield deeper insights into population structure and related spatial aspects. We agree on the value of having the most detailed and accurate data possible, but do not believe this standard should limit one to conducting only intensive experimental studies to provide detailed information on vital rates of terrestrial salamanders. The controlled experiment approach is extremely difficult and would be considerably less feasible than using population metrics to assess the status of plethodontid salamanders on forest landscapes at scales relevant to land management in the Pacific Northwest.     

Study on Soil and Pine-Seedling Zn and Mn and Predicting-Model Design

Soils were collected from 2-year (2-y) and 3-year (3-y) old red-pine seedling plots in two tree nurseries, Hayward in the north and Wilson in the southwestern part of Wisconsin State respectively, and equilibrated with 0.01 M Ca(NO₃)₂ for soil solution Zn and Mn (solu-Zn and Mn), and with 0.01 M Ca(NO₃)2+0.005 M EDTA for soil adsorbed Zn and Mn (ad-Zn and Mn). Buffering capacity of soil Zn and Mn (b-Zn and Mn) was obtained from the ratio of ad-Zn and Mn to the solu-Zn and Mn. The concerned traces in pine seedling needles (ndls), stems(sts) and roots (rts) were simultaneously measured.     

Is the endangered Fennoscandian arctic fox (Alopex lagopus) population genetically isolated?

The arctic fox population in Fennoscandia is on the verge of going extinct after not being able to recover from a severe bottleneck at the end of the 19th century. The Siberian arctic fox population, on the other hand, is large and unthreatened. In order to resolve questions regarding gene flow between, and genetic variation within the populations, a 294 bp long part of the mitochondrial hypervariable region 1 was sequenced. This was done for 17 Swedish, 15 Siberian and two farmed foxes. Twelve variable nucleotide sites were observed, which resulted in 10 different haplotypes. Three haplotypes were found in Sweden and seven haplotypes were found in Siberia. An analysis of molecular variance showed a weak, but significant, differentiation between the populations. No difference in haplotype diversity was found between the populations. A phylogenetic analysis revealed that the three Swedish haplotypes were not monophyletic compared to the Siberian haplotypes. These results indicate a certain amount of gene flow between the two populations, both before and after the bottleneck. Restocking the Fennoscandian population with arctic foxes from Siberia might therefore be a viable option.     

Are research priorities in Latin America in line with the nutritional problems of the population?

OBJECTIVE: Concordance of nutritional research priorities with the related burden of disease is essential to develop cost-effective interventions to address the nutritional problems of populations. The present study aimed to evaluate whether nutrition research priorities are in agreement with the population's nutritional problems in Latin America. DESIGN: The epidemiological profile was contrasted with the research priorities and research produced by academic institutions for each country. Qualitative analysis of research production by type of contribution to problem solving was also conducted. SETTINGS: Nine Latin American countries. RESULTS: Obesity (high body mass index (BMI)) and micronutrient deficiencies (anaemia) emerged as key problems, followed by stunting, breast-feeding/lactation and low birth weight. Wasting in children and women (low BMI) was uncommon. Concordance of ranked research priorities with the epidemiological profile of the country was generally good for nutrition-related chronic diseases, micronutrients and low birth weight, but not for undernutrition, stunting and breast-feeding. Studies on the efficacy and effectiveness of interventions were uncommon. CONCLUSIONS: The present research agenda insufficiently supports the goal of public health nutrition, which is to ensure the implementation of cost-effective nutrition programmes and policies. A more rational approach to define research priorities is needed.     

Selenium accumulation in a rapid‐cycling Brassica oleracea population responds to increasing sodium seienate concentrations

Because of their short life cycle, rapid‐cycling base populations (RCBP) of Brassica can act as model systems for investigating selenium (Se) metabolism in high sulfur (S) accumulating plants. To establish treatment responses for a B. oleracea RCBP, plants were grown in nutrient solutions containing 0, 3, 6, and 9 mg sodium seienate (Na₂SeO₄) L^‐1. Depletion of Se from nutrient solutions increased linearly with in‐creasing Na₂SeO₄ concentrations. Selenium accumulation ranged from 551 to 1,916 μg Se g^‐1 dry weight for leaf tissue, 267 to 1,165 μg Se g^‐1 dry weight for stem tissue, and 338 to 1,636 μg Se g^‐1 dry weight for root tissue. Selenium additions also resulted in linear increases in S accumulation in leaves and stems. Selenium supplementation has been shown to improve the health of individuals with low Se status. Because Brassica species are important vegetable and forage crops, their enrichment with Se maybe a good delivery system for mammalian diets.     

Perceptual selection and the unconscious selection of ‘volunteer’ seedlings in clonally propagated crops: an example with African cassava (<Emphasis Type="Italic">Manihot esculenta</Emphasis> Crantz) using ethnobotany and population genetics

The role of sexual reproduction in magnifying genetic diversity in clonally propagated crops is now well documented. But whereas many studies have emphasized the importance of perceptual distinctiveness and its role in arousing farmers’ curiosity towards plants with unusual morphological traits, few have considered its corollary, perceptual indistinctiveness. In this study, we investigated which factors influence farmers’ behaviours towards self-sown ‘volunteer’ seedlings of cassava (Manihot esculenta Crantz) in a cross-cultural survey in Gabon, Central Africa. Interviews revealed that farmers were seven times more likely to spare seedlings that resembled a named landrace compared to those that did not. Similarly, farmers were more likely to relax weeding pressures on cassava volunteers if they believed that volunteers were resurgences from old cuttings. The model fit significantly improved when cultural factors were accounted for, suggesting strong culture-dependent differences among communities in their perception of and attitudes towards cassava volunteers. An analysis of the structure of genetic diversity of cassava landrace populations at the community level showed that most landraces included singleton genotypes, even in villages where farmers imposed the strongest weeding pressures, suggesting that there is always some background incorporation of cassava seedlings. We show that by channelling the selective incorporation of cassava seedlings that are morphologically indistinguishable from familiar landraces, perceptual selection favors the recruitment, sometimes deliberate but more often unconscious, of new genotypes from plants germinating from seeds and contributes to balancing the disadvantages of strictly clonal propagation, while maintaining landraces within consensual combinations of perceptually distinct traits.