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91.
Anders Berglund Gunilla Rosenqvist Sarah Robinson-Wolrath 《Behavioral ecology and sociobiology》2006,60(2):281-287
In a sex role reversed pipefish, Syngnathus typhle, we found that basic life history allocations were directly influenced by sexual selection. We investigated time allocation to foraging and mating, respectively, in a choice experiment, giving males and females, of small or large body size, a choice between food and a potential partner. We found that males were more interested in foraging than mating, i.e., were more frequently observed in front of the food than in front of the partner, whereas females were more interested in the potential partner. This reflects sexual selection operating differently on the two sexes, as males and females are relatively similar in other life history traits, such as growth, mortality, age of maturity, dispersal, and parental expenditure. Moreover, large individuals allocated more time to mating activities, small to feeding. Individuals more interested in mating compared to food were subsequently more critical when given a choice between a large (high-quality) and a small (low-quality) partner, whereas individuals more interested in food were not selective. These findings are consistent with our predictions: sex-role reversed males can be relatively sure of achieving one or more matings, and should allocate more time to feeding and, hence, to parental investment, growth and/or future reproduction. Females, on the other hand, have more uncertain mating prospects and should allocate time to imminent reproductive activities, thereby foregoing other life history traits such as growth and future egg production. By this, they also sacrifice future fecundity and attractiveness. 相似文献
92.
Rare royal families in honeybees, Apis mellifera 总被引:1,自引:0,他引:1
Moritz RF Lattorff HM Neumann P Kraus FB Radloff SE Hepburn HR 《Die Naturwissenschaften》2005,92(10):488-491
The queen is the dominant female in the honeybee colony, Apis mellifera, and controls reproduction. Queen larvae are selected by the workers and are fed a special diet (royal jelly), which determines
caste. Because queens mate with many males a large number of subfamilies coexist in the colony. As a consequence, there is
a considerable potential for conflict among the subfamilies over queen rearing. Here we show that honeybee queens are not
reared at random but are preferentially reared from rare “royal” subfamilies, which have extremely low frequencies in the
colony's worker force but a high frequency in the queens reared. 相似文献
93.
Steen Smidt-Jensen John Philip Julia M. Zachary Sarah E. Fowler Bent Nørgaard-Pedersen 《黑龙江环境通报》1994,14(1):35-45
Of 2882 women allocated to either transabdominal CVS (TA) or transcervical CVS (TC) at two large obstetric centres in Denmark, 2707 had blood samples drawn before and 30 min after CVS for maternal serum-alpha-fetoprotein (MSAFP) measurement. 2535 of these women had cytogenetically normal pregnancies and 2091 of them went on to have samples drawn at the 18–20 week follow-up. Post-procedure MSAFP values were correlated to the biopsy method used, with mean MSAFP values significantly higher after TA than TC, 33 and 15 kU/l, respectively (P<0·001). Following TA procedures, 18 per cent of cases had feto-maternal transfusion higher than 0·1 ml; this occurred in only 5 per cent of TC cases. MSAFP levels were associated with spontaneous fetal loss in the TA group but not in the TC group. TC, however, was followed by more losses than TA. The post-CVS MSAFP value was positively correlated with the amount of villi aspirated. The difference in post-procedure elevation in MSAFP 30 min later (average 18 kU/l higher for TA than for TC) was not reflected in raised levels at the 18–20 week follow-up. Study medians at mid-trimester did not differ from reference group medians established from a group of singleton pregnancies with sonographically determined gestational age who did not experience invasive procedures and delivered normal infants. Our findings suggest that CVS does not compromise mid-trimester MSAFP for screening for neural tube defects (NTDs). Extremely high mid-trimester MSAFP values in the TC group could predict imminent loss. 相似文献
94.
Genetic variation in honeybee, Apis mellifera, populations can be considerably influenced by breeding and commercial introductions, especially in areas with abundant beekeeping. However, in southern Africa apiculture is based on the capture of wild swarms, and queen rearing is virtually absent. Moreover, the introduction of European subspecies constantly failed in the Cape region. We therefore hypothesize a low human impact on genetic variation in populations of Cape honeybees, Apis mellifera capensis. A novel solution to studying genetic variation in honeybee populations based on thelytokous worker reproduction is applied to test this hypothesis. Environmental effects on metrical morphological characters of the phenotype are separated to obtain a genetic residual component. The genetic residuals are then re-calculated as coefficients of genetic variation. Characters measured included hair length on the abdomen, width and length of wax plate, and three wing angles. The data show for the first time that genetic variation in Cape honeybee populations is independent of beekeeping density and probably reflects naturally occurring processes such as gene flow due to topographic and climatic variation on a microscale. 相似文献
95.
This paper summarizes those factors that have contributed to the degradation of the mangroves in El Salvador, and examines the implications of proposed changes in property rights to the mangroves for poor coastal communities. Current patterns of extraction and conversion in the mangrove ecosystem in El Salvador can be viewed through an entitlement lens that confers property right upon some actors, for certain uses, and denies them to others. Unfortunately, the present system of laws and regulations that governs resource use in the mangroves is contradictory and confusing. A number of laws currently are active that give entirely different directives about the use and transformation of the ecosystem. The rational and sustainable management of the mangroves cannot be secured without a redefinition of entitlement rights. This redefinition of entitlements, however, should take into account the needs of those whose livelihoods are intimately connected to the health of the ecosystem. 相似文献
96.
Fisheries catches are known to be widely underreported, and much of their value flows in informal markets. Goods and services that are not directly sold in a market also have a corresponding economic value, here termed ‘shadow value’, which can apply to discarded fish—or those that are consumed but not sold (e.g., subsistence catches). Here, we estimate the monetary value of fisheries catches in Panama that are landed but not reported, or that are discarded at sea; this includes catches from artisanal and industrial fleets, as well as recreational and subsistence fisheries. Based on available data, we estimate that the market and shadow value of unreported catches in Panama in 2010 was around US$92 million, equal to approximately 43% of the total reported landed value. In the case of discarded fish, the shadow value represents the potential but entirely unrealized economic benefit of landing such fish; in the case of unreported landings, unreported market value represents only the first link in the potentially sophisticated informal seafood economy. One must be careful in considering these results for policy. It is possible that, rather than seeking to capture these ‘lost’ benefits, fish that are discarded or unreported should not have been caught at all, for example, if they are juveniles or of threatened species; conversely, unreported subsistence catches are crucial for food security throughout the world. These results help contextualize the scale of unreported fisheries in economic terms, and can inform subsequent policies and strategies to ensure social, ecological, and economic sustainability. 相似文献
97.
This contribution presents an introduction to a series of papers on integrated scientific approaches presented at the San
Feliu Euroconference on transdisciplinary coastal management research. Coastal management is a challenging area for the integration
of social and natural sciences. The papers provide a basis for ongoing cross-disciplinary research. 相似文献
98.
Sarah J. Cowell Walter Wehrmeyer Peter W. Argust J. Graham S. Robertson 《Resources Policy》1999,25(4):421
This paper reflects on how sustainability is being interpreted both theoretically and in practice for the primary extraction industries. Two contrasting perspectives can be adopted: one states that continued extraction of non-renewable resources is a necessary part of sustainable development, whilst the other states that extraction of these resources must be greatly reduced or even eliminated. It is shown that these different approaches can be traced back to underlying, often unarticulated, assumptions about the acceptability of trade-offs between different societal goals; attitudes towards uncertainties in scientific analysis and the reliability of management systems; and the perceived appropriateness of system boundaries at different conceptual scales. These assumptions are founded in the self-perception of organisations and individuals about their roles in society, and the cultural context within which these organisations and individuals define their raison d'être. 相似文献
99.
100.
The 7.6 magnitude (Richter scale) earthquake that struck northern Pakistan on 8 October 2005 was devastating. This paper gauges success in targeting vulnerable families during the transition from relief to reconstruction through cash assistance provided by the Livelihood Support Cash Grants (LSCG) programme. Families without a male member, with a disabled male member aged between 18 and 60 years or with more than five children, defined as vulnerable, were provided with USD 50 per month for six months via a bank transfer. The LSCG scheme enrolled around 750,000 families and selected 267,402 vulnerable families to whom it disbursed a total of USD 86.95 million. Using a community‐based survey, this paper assesses leakage and under‐coverage (exclusion). Approximately 30 per cent of families received the cash grant. However, only one in two was eligible for the benefit, and one in two deserving families was excluded. This is a matter of grave concern. 相似文献