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51.
The fitness landscape—the mapping between genotypes and fitness—determines properties of the process of adaptation. Several small genotypic fitness landscapes have recently been built by selecting a handful of beneficial mutations and measuring fitness of all combinations of these mutations. Here, we generate several testable predictions for the properties of these small genotypic landscapes under Fisher's geometric model of adaptation. When the ancestral strain is far from the fitness optimum, we analytically compute the fitness effect of selected mutations and their epistatic interactions. Epistasis may be negative or positive on average depending on the distance of the ancestral genotype to the optimum and whether mutations were independently selected, or coselected in an adaptive walk. Simulations show that genotypic landscapes built from Fisher's model are very close to an additive landscape when the ancestral strain is far from the optimum. However, when it is close to the optimum, a large diversity of landscape with substantial roughness and sign epistasis emerged. Strikingly, small genotypic landscapes built from several replicate adaptive walks on the same underlying landscape were highly variable, suggesting that several realizations of small genotypic landscapes are needed to gain information about the underlying architecture of the fitness landscape.  相似文献   
52.
The bacterial diversity and abundance in two moraine lakes and two glacial meltwaters (5140, 5152, 5800 and 6350 m above sea level, respectively) in the remote Mount Everest region were examined through 16S rRNA gene clone library and flow cytometry approaches. In total, 247 clones were screened by RFLP and 60 16S rRNA gene sequences were obtained, belonging to the following groups: Proteobacteria (8% alpha subdivision, 21% beta subdivision, and 1% gamma subdivision), Cytophaga-Flavobacteria-Bacteroides (CFB) (54%), Actinobacteria (4%), Planctomycetes (2%), Verrucomicrobia (2%), Fibrobacteres (1%) and Eukaryotic chroloplast (3%), respectively. The high dominance of CFB distinguished the Mount Everest waters from other mountain lakes. The highest bacterial abundance and diversity occurred in the open moraine lake at 5152 m, and the lowest in the glacial meltwater at 6350 m. Low temperature at high altitude is considered to be critical for component dominancy. At the same altitude, nutrient availability plays a role in regulating population structure. Our results also show that the bacteria in Mount Everest may be derived from different sources.  相似文献   
53.
Vegetation recovery patterns in early volcanic succession   总被引:1,自引:0,他引:1  
Permanently plots were monitored from 1983 to the present on Mount Usu after the eruptions of 1977–78 which destroyed the pre-eruption vegetation by 1–3 m thick accumulations of ash and pumice in order to clarify the processes and mechanisms of succession. Until now, 163 species were recorded in the summit area. Most of these species were derived from vegetative reproduction throughout the volcanic deposits. Vegetative reproduction plays a major role on increases in cover. Although long-distance seed-dispersal species could immigrate to the crater basin, their cover increase was slow. Seedbank species only established in gullies where the original topsoil was exposed by erosion. Most annuais were supplied by the seedbank in the original topsoil and woody species originated via immigration, suggesting that the source greatly determines the species composition of establishing vegetation. Annual seedlings showed low survival, while overwintering perennial seedlings steadily established. Ground surface movements strongly restricted increases in plant cover and the distance from source vegetation was the principal determinant of plant density. Due to differences in disturbance intensity, successional rates were higher in the stable substrates outside gullies and lower on the exposed original topsoil in some gullies. Recipient of the Botanical Society Award of Young Scientists, 1994  相似文献   
54.
世界文化景观遗产的申报,是近年来国内越来越关注的话题,作为中国第一个成功以文化景观列入世界遗产名录的案例,五台山的申报过程为中国的文化景观遗产申报与研究提供了很多线索,尤其在突出普遍价值的认识及其保护管理方面,更是积累了一定的经验,同时也引发了新的思考。经过申报前后对遗产价值标准的对比研究及对保护管理的重新思考,认识到文化景观必须将自然、文化作为一个整体加以认知和保护,尤其要研究人与自然之间的作用机制,重视其中活态遗产的保护和展示。  相似文献   
55.
This study was designed to examine the role of vesicular-arbuscular mycorrhizae (VAM) and microsites on the growth of pioneer species. Flat, rill, near-rock, and dead lupine microsites were created in plots in barren areas of the Pumice Plain of Mount St. Helens. VAM propagules were added to the soil in half of the plots. Six pioneer species were planted into both VAM and non-VAM inoculated microsites. Plants in dead lupine microsites were greater in biomass than those in flat, rill, and near-rock microsites. Significant effects of VAM on plant biomass did not occur. Microsites continue to be important to plant colonization on the Pumice Plain, but VAM do not yet appear to play an important role. This may be due to limited nutrient availability and the facultatively mycotrophic nature of the colonizing plant species. It is unlikely that VAM play an important role in successional processes in newly emplaced nutrient-poor surfaces.  相似文献   
56.
57.
赵雨晴  游巍斌  林雪儿  何东进  文惠 《生态学报》2022,42(10):4011-4022
生态系统文化服务(CES)的核心是人与自然之间的情感连接,利益相关者视角下的参与式制图是感知与保护热点文化服务地区的有效方法。采用参与式制图与访谈、问卷相结合的方式调查了游客和居民2类群体对武夷山市CES的感知情况;利用空间分析、热点分析和相关性分析比较分析了游客和居民CES的感知差异特征、影响因素及其空间分布格局。结果表明:(1)除了居民月收入对感知有影响外,游客和居民对武夷山市CES认知基本不受人口学特征(性别、年龄、职业和文化程度)的影响(P>0.05);(2)居民的CES价值人均支付保护意愿较游客高。文化遗产、游憩与生态旅游、教育、美学价值是游客和居民都重视的4类子文化服务。游客对文化遗产价值服务的支付意愿最高,而居民则对教育价值服务支付意愿最高。(3)居民对CES价值感知分布空间范围较广,几乎涵盖了武夷山市大部分乡镇;而游客则相对集中,主要位于旅游点密集区域,对其他地区的感知程度较低。CES价值冷热感知程度与旅游点分布呈现相同的空间分布格局,游客和居民对CES价值热点区的感知强度从南向北逐渐降低。(4)从不同文化服务类型权衡/协同关系上看,除了“精神与宗教价值”和“游憩...  相似文献   
58.
Abstract: The Mount Graham red squirrel (Tamiasciurus hudsonicus grahamensis) is constrained to the Pinaleño Mountains in southeastern Arizona, USA. The population's endangered status and extensive forest damage from insects and fire warrants a better understanding of habitat variables important for nest site selection. We examined characteristics of cavity (n = 91) and drey (n = 38) nests and compared these to random sites (n = 113). Dreys were found primarily in Engelmann spruce (Picea engelmannii) and corkbark fir (Abies lasiocarpa var. arizonica). Cavity nests occurred primarily in aspen (Populus tremuloides) and corkbark fir. Squirrels selected nest sites with higher canopy cover and more corkbark fir, decayed logs, and living trees. Forest management plans emphasizing thinning must consider how altering these habitat characteristics could affect availability and suitability of tree stands for nesting squirrels.  相似文献   
59.
Forecasts of widespread range shifts with climate change stem from assumptions that climate drives species' distributions. However, local adaptation and biotic interactions also influence range limits and thus may impact range shifts. Despite the potential importance of these factors, few studies have directly tested their effects on performance at range limits. We address how population‐level variation and biotic interactions may affect range shifts by transplanting seeds and seedlings of western North American conifers of different origin populations into different competitive neighborhoods within and beyond their elevational ranges and monitoring their performance. We find evidence that competition with neighboring trees limits performance within current ranges, but that interactions between adults and juveniles switch from competitive to facilitative at upper range limits. Local adaptation had weaker effects on performance that did not predictably vary with range position or seed origin. Our findings suggest that competitive interactions may slow species turnover within forests at lower range limits, whereas facilitative interactions may accelerate the pace of tree expansions upward near timberline.  相似文献   
60.
The genus Menegazzia (Parmeliaceae, lichenized ascomycetes) in Malaysia and Indonesia is studied. Some specimens from Papua New Guinea are also included. The great majority of available specimens are from Kinabalu Park, State of Sabah, Malaysia. Three species are described as new to science, namely the two sorediate species M. capitata (from Sabah and Pahang in Malaysia) and M. sabahensis (from Sabah), and the fertile, primary species M. monospora (from Sabah and Papua New Guinea). M. asahinae , M. dissoluta , and M. efflorescens are reported for the first time from Malaysia, and M. subsimilis is reported for the first time from Malaysia and Indonesia. The subgenus Megamenegazzia is newly described to accommodate the large, broad-lobed species with numerous perforations on the lower surface. M. efflorescens is selected as the type species for the new subgenus. Notes are also provided on the type specimens of Hypogymnia pectinatula , a species originally considered as belonging to Menegazzia .  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 153 , 489–499.  相似文献   
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