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951.
952.
Explaining cooperation remains a central topic for evolutionary theorists. Many have argued that group selection provides such an explanation: theoretical models show that intergroup competition could have given rise to cooperation that is costly for the individual. Whether group selection actually did play an important role in the evolution of human cooperation, however, is much debated. Recent experiments have shown that intergroup competitions do increase human cooperation, which has been taken as evidence for group selection as a mechanism for the evolution of cooperation. Here we challenge this standard interpretation. Competitions change the payoff structure by creating a threshold effect whereby the group that contributes more earns an additional prize, which creates some incentive for individuals to cooperate. We present four studies that disentangle competition and thresholds, and strongly suggest that it is thresholds – rather than competitions per se – that increase cooperation. Thus, prior intergroup competition experiments provide no evidence of a unique or special role for intergroup competition in promoting human cooperation, and shed no light on whether group selection shaped human evolution. 相似文献
953.
John Bradby Blake (1745–1773) first visited Canton as a supercargo for the British East India Company in 1767/68. He returned as a resident supercargo in July 1769. Between then and his untimely death in 1773, in collaboration with one or more Chinese artists, he produced over 150 paintings of Chinese plants, many of which are illustrated in exquisite botanical detail. These paintings and the associated archives in the Oak Spring Garden Library at the Oak Spring Garden Foundation (OSGF) provide a detailed glimpse into an interesting life and a previously little known dimension of the social and scientific interactions between the British and Chinese in the late 18th century. 相似文献
954.
Jamieson C. Botsch Scott T. Walter Jordan Karubian Nelson González Emily K. Dobbs Berry J. Brosi 《Journal of Insect Conservation》2017,21(4):633-643
Habitat loss is a major driver of bee declines worldwide, and is of key relevance in the tropics given high deforestation rates, but we continue to have a poor understanding of the impact of land-cover change on tropical bee communities. Orchid bees (Apidae: Euglossini) are critical long-distance pollinators and may be highly susceptible to forest fragmentation given their reliance on forest habitat. Previous studies on the impact of forest fragmentation on euglossines have been geographically limited, have largely ignored β-diversity, and have not compared fragments with continuous forest. To contribute to addressing these gaps, we sampled male euglossine bees in 18 forest fragments (area range: 2.5–33 ha) and at eight locations within a large (3500 ha) continuous forest in the Chocó biodiversity hotspot of Ecuador during the dry season in 2014. We assessed how euglossine abundance, richness, and evenness related to fragment area, isolation, and edge:area ratio. We also compared fragments to continuous forest, in terms of α- and β-diversity. In fragments, a single species (Euglossa tridentata) comprised 78% of captures, and we found no significant effect of fragment area, isolation, or edge on abundance, richness, or evenness among fragments. Forest fragments and continuous forest differed in both community composition and evenness, but not in abundance or species richness. Spatial turnover (β-diversity) showed a non-significant trend toward changing more rapidly in continuous forest relative to fragments. These results underscore the conservation value of continuous forest for orchid bee diversity. 相似文献
955.
Anell Olivos-Meza Cristina Velasquillo Martínez Brenda Olivos Díaz Carlos Landa-Solís Mats Brittberg Raul Pichardo Bahena Carmina Ortega Sanchez Valentin Martínez Enrique Alvarez Lara José Clemente Ibarra-Ponce de León 《Cell and tissue banking》2017,18(3):369-381
To compare the quality of the repair tissue in three-dimensional co-culture of human chondrocytes implanted in an in vivo model. Six cadaveric and five live human donors were included. Osteochondral biopsies from the donor knees were harvested for chondrocyte isolation. Fifty percent of cadaveric chondrocytes were expanded until passage-2 (P2) while the remaining cells were cryopreserved in passage-0 (P0). Fresh primary chondrocytes (P0f) obtained from live human donors were co-cultured. Three-dimensional constructs were prepared with a monolayer of passage-2 chondrocytes, collagen membrane (Geistlich Bio-Gide®), and pellet of non-co-cultured (P2) or co-cultured chondrocytes (P2 + P0c, P2 + P0f). Constructs were implanted in the subcutaneous tissue of athymic mice and left for 3 months growth. Safranin-O and Alcian blue staining were used to glycosaminoglycan content assessment. Aggrecan and type-II collagen were evaluated by immunohistochemistry. New-formed tissue quality was evaluated with an adaptation of the modified O’Driscoll score. Histological quality of non-co-cultured group was 4.37 (SD ±4.71), while co-cultured groups had a mean score of 8.71 (SD ±3.98) for the fresh primary chondrocytes and 9.57 (SD ±1.27) in the cryopreserved chondrocytes. In immunohistochemistry, Co-culture groups were strongly stained for type-II and aggrecan not seen in the non-co-cultured group. It is possible to isolate viable chondrocytes from cadaveric human donors in samples processed in the first 48-h of dead. There is non-significant difference between the numbers of chondrocytes isolated from live or cadaveric donors. Cryopreservation of cadaveric primary chondrocytes does not alter the capability to form cartilage like tissue. Co-culture of primary and passaged chondrocytes enhances the histological quality of new-formed tissue compared to non-co-cultured cells. 相似文献
956.
957.
François Courchesne Marie-Claude Turmel Benoît Cloutier-Hurteau Simon Constantineau Lara Munro Michel Labrecque 《International journal of phytoremediation》2017,19(6):545-554
The phytoextraction of the trace elements (TEs) As, Cd, Cu, Ni, Pb, and Zn by willow cultivars (Fish Creek, SV1 and SX67) was measured during a 3-year field trial in a mildly contaminated soil. Biomass ranged from 2.8 to 4.4 Mg/ha/year at 30,000 plants/ha. Shoots (62%) were the main component followed by leaves (23%) and roots (15%). Biomass was positively linked to soluble soil dissolved organic carbon, K, and Mg, while TEs, not Cd and Zn, had a negative effect. The TE concentration ranking was: Zn > Cu > Cd > Ni, Pb > As, and distribution patterns were: (i) minima in shoots (As, Ni), (ii) maxima in leaves (Cd, Zn), or (iii) maxima in roots (Cu, Pb). Correlations between soil and plant TE were significant for the six TEs in roots. The amounts extracted were at a maximum for Zn, whereas Fish Creek and SV1 extracted more TE than SX67. More than 60% (91–94% for Cd and Zn) of the total TE was in the aboveground parts. Uptake increased with time because of higher biomass. Fertilization, the selection of cultivars, and the use of complementary plants are required to improve productivity and Cd and Zn uptake. 相似文献
958.
959.
L. A. Crespo-Herrera E. Akhunov L. Garkava-Gustavsson K. W. Jordan C. M. Smith R. P. Singh I. Åhman 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2014,127(9):1963-1973
Key message
Identification of novel resistance QTL against wheat aphids. First QTL-resistance report for R. padi in wheat and chromosome 2DL for S. graminum . These sources have potential use in wheat breeding.Abstract
The aphids Rhopalosiphum padi and Schizaphis graminum are important pests of common wheat (Triticum aestivum L.). Characterization of the genetic bases of resistance sources is crucial to facilitate the development of resistant wheat cultivars to these insects. We examined 140 recombinant inbred lines (RILs) from the cross of Seri M82 wheat (susceptible) with the synthetic hexaploid wheat CWI76364 (resistant). RILs were phenotyped for R. padi antibiosis and tolerance traits. Phenotyping of S. graminum resistance was based on leaf chlorosis in a greenhouse screening and the number of S. graminum/tiller in the field. RILs were also scored for pubescence. Using a sequence-based genotyping method, we located genomic regions associated with these resistance traits. A quantitative trait locus (QTL) for R. padi antibiosis (QRp.slu.4BL) that explained 10.2 % of phenotypic variation was found in chromosome 4BL and located 14.6 cM apart from the pubescence locus. We found no association between plant pubescence and the resistance traits. We found two QTLs for R. padi tolerance (QRp.slu.5AL and QRp.slu.5BL) in chromosomes 5AL and 5BL, with an epistatic interaction between a locus in chromosome 3AL (EnQRp.slu.5AL) and QRp.slu.5AL. These genomic regions explained about 35 % of the phenotypic variation. We re-mapped a previously reported gene for S. graminum resistance (putatively Gba) in 7DL and found a novel QTL associated with the number of aphids/tiller (QGb.slu-2DL) in chromosome 2DL. This is the first report on the genetic mapping of R. padi resistance in wheat and the first report where chromosome 2DL is shown to be associated with S. graminum resistance. 相似文献960.
Daniela Camargos Costa Ana Paula Madureira Lara Cotta Amaral Bruno Ant?nio Marinho Sanchez Luciano Teixeira Gomes Cor Jésus Fernandes Fontes Jean Ezequiel Limongi Cristiana Ferreira Alves de Brito Luzia Helena Carvalho 《Memórias do Instituto Oswaldo Cruz》2014,109(1):21-28
The polymerase chain reaction (PCR)-based methods for the diagnosis of malaria
infection are expected to accurately identify submicroscopic parasite carriers.
Although a significant number of PCR protocols have been described, few studies have
addressed the performance of PCR amplification in cases of field samples with
submicroscopic malaria infection. Here, the reproducibility of two well-established
PCR protocols (nested-PCR and real-time PCR for the Plasmodium 18
small subunit rRNA gene) were evaluated in a panel of 34 blood field samples from
individuals that are potential reservoirs of malaria infection, but were negative for
malaria by optical microscopy. Regardless of the PCR protocol, a large variation
between the PCR replicates was observed, leading to alternating positive and negative
results in 38% (13 out of 34) of the samples. These findings were quite different
from those obtained from the microscopy-positive patients or the unexposed
individuals; the diagnosis of these individuals could be confirmed based on the high
reproducibility and specificity of the PCR-based protocols. The limitation of PCR
amplification was restricted to the field samples with very low levels of
parasitaemia because titrations of the DNA templates were able to detect < 3
parasites/µL in the blood. In conclusion, conventional PCR protocols require careful
interpretation in cases of submicroscopic malaria infection, as inconsistent and
false-negative results can occur. 相似文献