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1.
Lopatto D Alvarez C Barnard D Chandrasekaran C Chung HM Du C Eckdahl T Goodman AL Hauser C Jones CJ Kopp OR Kuleck GA McNeil G Morris R Myka JL Nagengast A Overvoorde PJ Poet JL Reed K Regisford G Revie D Rosenwald A Saville K Shaw M Skuse GR Smith C Smith M Spratt M Stamm J Thompson JS Wilson BA Witkowski C Youngblom J Leung W Shaffer CD Buhler J Mardis E Elgin SC 《Science (New York, N.Y.)》2008,322(5902):684-685
2.
The conservation of threatened frugivorous primates (e.g. chimpanzees) and birds in the Albertine Rift Ecoregion rainforests requires the conservation of food tree species aided by an understanding of their natural regeneration and population trends. However, little is known of the population structure and regeneration patterns of a wide range of multiple-use tree species in many of these forests. 相似文献
3.
Nurseries are risky ventures, even in conducive operating environments. Unlike many of their international counterparts, financial
objectives are usually important to South African outreach nurseries, to generate funds for projects and/or to enhance local
livelihoods. However, most are situated in low-income areas where residents have limited spending power. This paper examines
the commercial viability of ten outreach nurseries from six provinces, with a range of conservation objectives. Management
performance was assessed through correspondence and financial ratio analyses. Although seven projects had built up steady
markets, this took 5–8 years to achieve, even in intensively funded projects. Only one nursery had achieved a steady annual
net profit. The prolonged establishment phases impacted negatively on participants’ livelihoods and project processes. Marketing
difficulties included a lack of markets, nurseries being located far from markets, pricing difficulties, inadequate transport
and limited marketing communications. Seasonal factors exacerbated liquidity shortfalls. Conservation activities such as greening
and rehabilitation programmes provided markets, but medicinal plant nurseries struggled to achieve both conservation and socio-economic
objectives, largely through difficulties experienced in providing seedlings at prices that subsistence sector resource users
could afford. To achieve commercial viability, outreach enterprises need to adhere to business fundamentals viz. effective
planning, management and coordination of resources, monitoring and control. Thorough viability studies are crucial. Alternate
natural resource management and income generating strategies need to be evaluated, as a nursery may not be the best means
of achieving these. The current Build–Operate–Transfer approach to projects by many supporting organisations is cause for
concern as even small-scale projects usually require intensive support. 相似文献
4.
1. A study of the incidence of chromosome instability in the Japanese quail as assessed by sister chromatid exchange (SCE) and fragile site identification in chromosomes was conducted in two parent breeds and their F1 and F2 generations.
2. The mean incidence of SCEs was 6.02 ± 0.45 and the frequency of fragile sites was 1.17 ± 0.79.
3. There were moderately negative correlations of 0.51–0.64 between chromosome instability and fertility in the F1 and 0.10–0.23 in the F2. The hatch of fertilised eggs was negatively correlated with the number of SCE in male (0.31) and female (0.33) F1 and was lower in P (0.18 and 0.19, respectively), whereas the correlations were similar for the number of fragile sites in both generations (0.51–0.62). 相似文献
5.
Tumorigenicity in human melanoma cell lines controlled by introduction of human chromosome 6 总被引：32，自引：0，他引：32
J M Trent E J Stanbridge H L McBride E U Meese G Casey D E Araujo C M Witkowski R B Nagle 《Science (New York, N.Y.)》1990,247(4942):568-571
Chromosome banding analysis of human malignant melanoma has documented the nonrandom alteration of chromosome 6. To determine the relevance of chromosome 6 abnormalities in melanoma, a normal chromosome 6 was directly introduced into melanoma cell lines. The resulting (+6) microcell hybrids were significantly altered in their phenotypic properties in culture and lost their ability to form tumors in nude mice. The loss of the chromosome 6 from melanoma microcell hybrids resulted in the reversion to tumorigenicity of these cells in mice. The introduction of the selectable marker (psv2neo) alone into melanoma cell lines had no effect on tumorigenicity. These results support the idea that one or more genes on chromosome 6 may control the malignant expression of human melanoma. 相似文献
6.
Delali?B.?K.?DovieEmail author E.?T.?F.?Witkowski Charlie?M.?Shackleton 《Agriculture and Human Values》2005,22(1):87-103
There is, at present, little precise understanding of the relative contributions of the various income streams used by impoverished rural households in southern Africa. The impact of household profiles on overall income also is not well understood. There is, therefore, little consideration of these factors in national economic accounting. This paper is an attempt to reduce this gap in knowledge by reflecting on the relative contribution of agro-pastoralism, secondary woodland resources, and formal and informal cash income streams to households in the semi-arid rural village of Thorndale, Limpopo Province, South Africa. In the absence of jobs and confronted with high migrant labor, households with open access to natural resources derived more benefits from land-based livelihoods than cash income streams (i.e., 57.5 % vs. 42.5 %). Total livelihood income was valued at US$2887 per household per annum. A significant correlation between monetary values derived from crops and formal wages was established, and it was found that households with high cash incomes tended to invest more in crop production. Over 80 of households were male-headed. Of these heads of household, more than 60 were long-term migrants to urban areas, leaving household decision-making to the women. The low literacy rates of women have deprived them of paid jobs outside the area and, therefore, have increased their dependence on crops (62%) and secondary woodlands resources (60%). This was further reflected in the proportion of households in which females were the main contributors of cash income (9.7%), or joint contributors with men (24.4%). Various positive correlations were established between the number of women per household and the three land-based livelihoods. This implied that womens total control over such activities was mostly a result of the absence of men and not a typical phenomenon. In spite of this control, it was not positively reflected in the lives of majority of the women. Households differed in their participation in livelihood activities. Household size influenced the level of production and was positively correlated with the value of secondary woodland resources and crops. The study shows the interdependence of land-based livelihood sources and the impact of household features on production and consumption. Policies that focus on livelihood options need to recognize and accommodate associated household dynamics.Delali B. K. Dovie is a conservation biologist with interests in agricultural and natural resource economics and conservation, rural sociology, and global environmental change issues. He is currently a START/IGBP African Doctoral Fellow, and Honorary Research Fellow, School of Animal, Plant & Environmental Sciences, University of the Witwatersrand, South Africa.E. T. F. Witkowski is an ecologist with expertise in eco-physiology, restoration and plant ecology, and ethnobotany. He is Professor and Director of the Restoration and Conservation Biology Research Group, University of the Witwatersrand, South Africa.Charlie M. Shackleton is an ecologist and Professor at the Department of Environmental Science, Rhodes University with many years of experience and good working knowledge of agro-ecological research, natural resources, plant population dynamics, and ethnobotany. 相似文献
7.
Wyrwicz LS von Grotthuss M Pas J Rychlewski L 《Science (New York, N.Y.)》2004,303(5655):168; author reply 168
8.
Baobab fruit are harvested and used throughout Africa as an important source of food and are sold to generate income. Commercial use is increasing rapidly as derivatives of the fruit such as baobab seed oil and fruit pulp are being exported to Europe and North America. The cash derived from the sale of fruit support thousands of rural people. This study examines baobab fruit yields in an area being harvested for commercial use. It represents baobab populations and harvesting scenarios typically found in Southern Africa and is the first study in Africa to combine demographic and production data in determining baobab fruit yields.Fruit production was examined across five land-use types (nature reserves, rocky outcrops, plains, fields and villages) and over three consecutive years. Factors assessed included differences in life-stage, tree size, land-use type, inter-annual variation and quantifiable fruit predation.Results showed that adult trees produced 8 times more fruit than sub-adult trees. Fruit production fluctuated between size-classes and exhibited weak linear and logarithmic trends between fruit production and dbh and crown volume, respectively. There was high variation between trees with 41% of adult trees consistently producing <5 fruit per year, which we classed as ‘poor-producers’. Different land uses showed no significant differences in fruit production per tree, but where baboons were present, in nature reserves and rocky outcrops, predation of immature fruit resulted in up to 85% fruit loss. Villages and fields had the highest tree density and yielded the most fruit/ha. Inter-annual variation was significant with a two and a half fold difference between the highest and lowest year.The results of this study are important for economic planning and management and are key to determining sustainable harvesting levels of baobab fruit in Southern Africa. 相似文献
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10.
Edward Witkowski Jacek Waga Krystyna Witkowska Marcin Rapacz Magdalena Gut Amelia Bielawska Helena Luber Adam J. Lukaszewski 《Euphytica》2008,159(3):377-384
Subunits of high molecular weight glutenins strongly influence wheat bread making quality and can be associated with important
agronomic traits. Polish winter wheats show a significant quantitative dominance of the null allele over the coding alleles of the Glu-A1 locus. To identify the causes of such skewed distribution, 116 F5 lines obtained from six cross combinations were analyzed for their HMW glutenin subunits and 11 agronomic characteristics,
such as plant height and uniformity, leaf blotch and leaf rust resistance, grain yield per plot, number of grains per ear,
grain yield per ear, 1000 kernel weight, frost tolerance, total protein content and the SDS-sedimentation value. The SDS-sedimentation
value, resistance to leaf blotch and frost tolerance showed statistically significant associations with the status of the
Glu-A1 locus. It appears that chromosome 1A with the null allele at Glu-A1 carries a closely linked locus responsible for frost tolerance. With early strong selection for winter hardiness, the null
allele of Glu-A1 becomes fixed in advanced breeding materials despite its strong negative impact on the end use quality. 相似文献