Multiple paternity and female sperm usage along egg-case strings of the knobbed whelk, <Emphasis Type="Italic">Busycon carica</Emphasis> (Mollusca; Melongenidae)

We used genotypic data from three highly polymorphic microsatellite loci (two autosomal and one sex-linked) to examine micro-spatial and temporal arrangements of genetic paternity for more than 1,500 embryos housed along 12 egg-case strings of the knobbed whelk, Busycon carica. Multiple paternity proved to be the norm in these single-dam families, with genetic contributions of several sires (at least 3.5 on average) being represented among embryos within individual egg capsules as well as along the string. Two strings were studied in much greater detail; five and seven fathers were identified, none of which was among the several males found in consort with the female at her time of egg-laying. Each deduced sire had fathered roughly constant proportions of embryos along most of the string, but those proportions differed consistently among fathers. A few significant paternity shifts at specifiable positions along an egg-case string were also observed. Although the precise physical mechanisms inside a female whelk’s reproductive tract remain unknown, our genetic findings indicate that successive fertilization events (and/or depositions of zygotes into egg capsules) normally occur as near-random draws from a well-but-not-perfectly blended pool of gametes (or zygotes) stemming from stored ejaculates, perhaps in different titers, of a dam’s several mates.     

A Microcosm Approach to the Detection of the Effects of Herbicide Spray Drift in Plant Communities

It is often difficult to measure and predict the impacts of toxic chemicals, such as herbicides, on natural communities. This is especially true under conditions of spray drift when the amount received by the organisms downwind from the sprayer may be at sub-lethal doses. Laboratory experiments are either artificial, or have not been generally carried out over long enough time periods, to be realistic. Field experiments are often difficult because of the high variability inherent in natural populations. Here an intermediate microcosm approach was used, where standardized artificial communities (eight dicotyledons with and without a grass) were tested. The artifical communities included species typical of British woodland margins, hedgerows and field margins; communities with a high conservation interest, yet potentially under threat from spray drift. The microcosms were placed downwind of a sprayer and exposed to one of the following herbicides: glyphosate, mecoprop and MCPA. This approach ensures that the communities were standardized at the start and have been exposed to realistic doses of herbicide. The experiments reported here were carried out for at least three years with exposures to herbicides repeated each year. The effects of differential herbicide exposure downwind of the sprayer were measured on species yield, flowering performance, seed production, seed viability and invasion by new species. Responses were extremely variable, but all species showed some effects in some years. Some patterns emerged. For example, one group of species appeared to be more successful near to the sprayer. This was particularly true of the grass when exposed to MCPA and mecoprop. The performance of most species was reduced under the sprayer, and there was a general recovery with increasing distance downwind. A few species showed increased performance in the intermediate downwind zone (2–4 m) and this may be due to a hormonal effect on growth processes, or an effect of reduced interference from other community members. Generally, there were few effects on seed production or seed viability. An important result was that most effects were confined within an 8 m zone, as there were few significant differences between plants exposed at 8 m and those untreated. Although damaging effects were found in the immediate downwind zone from the sprayer, the restriction of effects to 8 m suggests that a buffer zone of this size would be adequate to protect sensitive habitats from most deleterious impacts on community processes.     

Country specific low carbon commitments versus equitable and practical company specific decarbonisation targets

Environment, Development and Sustainability - Concerns about the impact of climate change and the need for stabilising a global temperature rise to below 2 degrees Celsius are driving the...     

A Process investigation of realistic job previews: Mediating variables and channels of communication

A laboratory experiment was conducted to investigate the role of three possible mediating variables (job attitude, job knowledge, and job acceptance intention) to explain the effects of realistic job previews (RJPs) on entry-level outcomes. In addition, the effectiveness of an oral realistic job preview presented by an employment interviewer was compared to a written RJP. Sixty undergraduate student volunteers were randomly assigned to one of three conditions: (1) an oral RJP presented to job applicants by the employment interviewer during an employment interview; (2) a written RJP given to job applicants to read before an employment interview; and (3) a control condition in which job applicants received general job information from the interviewer during an employment interview. Results indicated that knowledge was an important mediator of RJP effects on several entry-level outcomes whereas attitude and job acceptance intention did not mediate RJP effects although both were strongly related to job acceptance decisions. In addition, the oral RJP was more effective than both the written RJP and general job information in creating positive preceptions of interviewer and organization honesty. Both the oral and the written RJP lowered subjects' job expectations and increased role clarity in comparison to the control group but did not affect job acceptance or commitment to job choice. The implications for future RJP research and application are discussed.     

对太平洋岛屿的全球国际水域评估:跨界、水资源短缺和沿海渔业问题

跨界、水资源短缺和渔场问题以近期完成的太平洋岛屿全球国际水域评估(GIWA)结果为基础进行了讨论.太平洋岛屿水域面积3000万km2,占全球海洋面积的大约12%,在地理、人口和发展等方面具有多样性.全球性变化,尤其是海平面上升和海面温度的提高,是最主要的跨界关注的问题,因为它影响着生活的方方面面.水资源短缺和不可持续发展的海洋渔业问题也是讨论的议题,因为这些问题在可预见的将来会主宰整个地区,在此以斐济、基里巴斯、汤加的例子加以说明.社会经济因素,例如人口快速增长、城市化、传统生活方式的解体以及现金经济的发展,加剧了环境问题.本文提出了有助于解决这些问题的政策方案.     

Psychosocial origins of conflict over pest control strategies

The achievement of consensus on strategies of pest control continues to be an elusive goal, one that is hindered by continuing, and often acrimonious, conflict. Psychosocial factors, such as personal biases, play an important, often hidden role, in maintaining mutual misunderstanding and hostility. One result of personal biases, such as intellectual preferences or styles, is that radically different perceptions of the “problem” are held by antagonists. As a consequence, there is little chance of developing common ground upon which to discuss solutions. In this paper, the role of intellectual style in the spruce budworm controversy is outlined, together with a discussion of the more general problems that personal biases create in the development of integrated pest management strategies.     

How effective are broad-scale nutrient mass balances for determining the sustainability of lot-feed manure application?

Nutrient mass balances have been used to assess a variety of land resource scenarios, at various scales. They are widely used as a simple basis for policy, planning, and regulatory decisions but it is not clear how accurately they reflect reality. This study provides a critique of broad-scale nutrient mass balances, with particular application to the fertiliser use of beef lot-feeding manure in Queensland.Mass balances completed at the district and farm scale were found to misrepresent actual manure management behaviour and potentially the risk of nutrient contamination of water resources. The difficulties of handling stockpile manure and concerns about soil compaction mean that manure is spread thickly over a few paddocks at a time and not evenly across a whole farm. Consequently, higher nutrient loads were applied to a single paddock less frequently than annually. This resulted in years with excess nitrogen, phosphorus, and potassium remaining in the soil profile. This conclusion was supported by evidence of significant nutrient movement in several of the soil profiles studied.Spreading manure is profitable, but maximum returns can be associated with increased risk of nutrient leaching relative to conventional inorganic fertiliser practices. Bio-economic simulations found this increased risk where manure was applied to supply crop nitrogen requirements (the practice of the case study farms, 200–5000 head lot-feeders).Thus, the use of broad-scale mass balances can be misleading because paddock management is spatially heterogeneous and this leads to increased local potential for nutrient loss. In response to the effect of spatial heterogeneity policy makers who intend to use mass balance techniques to estimate potential for nutrient contamination should apply these techniques conservatively.     

Proposed guidelines for diagnosis of chromosome mosaicism in amniocytes based on data derived from chromosome mosaicism and pseudomosaicism studies

Currently, accepted protocol which has been developed at the Prenatal Diagnosis Laboratory of New York City (PDL) requires that when a chromosome abnormality is found in one or more cells in one flask, another 20–40 cells must be examined from one or two additional flasks. Chromosome mosaicism is diagnosed only when an identical abnormality is detected in cells from two or more flasks. In a recent PDL series of 12 000 cases studied according to this protocol, we diagnosed 801 cases (6.68 per cent) of single-cell pseudomosaicism (SCPM), 126 cases (1.05 per cent) of multiple-cell pseudomosaicism (MCPM), and 24 cases (0.2 per cent) of true mosaicism. Pseudomosaicism (PM) involving a structural abnormality was a frequent finding (2/3 of SCPM and 3/5 of MCPM), with an unbalanced structural abnormality in 55 per cent of SCPM and 24 per cent of MCPM. We also reviewed all true mosaic cases (a total of 50) diagnosed in the first 22000 PDL cases. Of these 50 cases, 23 were sex chromosome mosaics and 27 had autosomal mosaicism; 48 cases had numerical abnormalities and two had structural abnormalities. Twenty-five cases of mosaicism were diagnosed in the first 20 cells from two flasks, i.e., without additional work-up, whereas the other 25 cases required extensive work-up to establish a diagnosis (12 needed additional cell counts from the initial two culture flasks; 13 required harvesting a third flask for cell analysis). Our data plus review of other available data led us to conclude that rigorous efforts to diagnose true mosaicism have little impact in many instances, and therefore are not cost-effective. On the basis of all available data, a work-up for potential mosaicism involving a sex chromosome aneuploidy or structural abnormality should have less priority than a work-up for a common viable autosomal trisomy. We recommend revised guidelines for dealing with (1) a numerical versus a structural abnormality and (2) an autosomal versus a sex chromosome numerical aneuploidy. Emphasis should be placed on autosomes known to be associated with phenotypic abnormalities. These new guidelines, which cover both flask and in situ methods, should result in more effective prenatal cytogenetic diagnosis and reduced patient anxiety.