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51.
The transition from the Lower to the Middle Paleolithic in the Levant is a crucial event in human evolution, since it may involve the arrival of a new human population. In the current study, we present thermoluminescence (TL) dates obtained from 32 burnt flints retrieved from the late Lower Paleolithic (Acheulo-Yabrudian) and Early Middle Paleolithic (Mousterian) layers of Misliya Cave, Mount Carmel, Israel. Early Middle Paleolithic industries rich in Levallois and laminar products were assigned mean ages ranging from ∼250 to ∼160 ka (thousands of years ago), suggesting a production of this industry during MIS 7 and the early part of MIS 6. The mean ages obtained for the samples associated with the Acheulo-Yabrudian (strengthened by an isochron analysis) indicate a production of this cultural complex ∼250 ka ago, at the end of MIS 8. According to the Misliya TL dates, the transition from the Lower to the Middle Paleolithic in the site took place at the limit MIS 8/7 or during the early part of MIS 7. The dates, together with the pronounced differences in lithic technology strongly suggest the arrival of a new population during this period.  相似文献   
52.
The palaeoecological visibility of historical human impact on natural ecosystems in tropical East Africa is strongly impeded by an overriding dominant signature of climate change at decadal‐to‐millennial time scales. Better knowledge of the relative magnitude and timing of present and past human impact and climate variability is, however, instrumental to properly assess the resilience, and recovery potential, of East Africa's natural ecosystems. Here, we briefly review comprehensive previous attempts to assess past ecosystem responses to climate change and human impact. We further discuss some key issues of climate‐human‐ecosystem relationships in a multidisciplinary framework and address some future challenges and outcomes, which may pave the way to a better understanding of past climate‐human‐ecosystem interaction‐ in tropical Africa.  相似文献   
53.
In many respects, recent East European migrants in the UK look like past migrants to the UK: they left poorer parts of the world in search of work and the better life in the UK. But in other respects, they look different: they are white. Their putative whiteness, however, has not exempted them from the effects of racism. But while there is growing evidence of how they have been targets of racism, less attention has been focused on how they are also perpetrators of racism. The purpose of this paper is to compare the ways Hungarians and Romanians wield ‘race’ to assert and defend the relatively privileged position their putative whiteness affords them in the UK's segmented labour market. I argue that these migrants mark, evaluate and rank difference in racialized ways to secure both social-psychological and material benefits.  相似文献   
54.
Habitat‐associated trait divergence may vary across ontogeny if there are strong size‐related shifts in selection pressures. We quantified patterns of phenotypic divergence in Nile perch (Lates niloticus) from ecologically distinct wetland edge and forest edge habitats in Lake Nabugabo, Uganda, and we compared patterns of divergence across three size classes to determine whether trends are consistent through Nile perch ontogeny. We predicted that inter‐habitat variation in biotic (e.g. vegetation structure) and abiotic (e.g. dissolved oxygen concentration) variables may create divergent selective regimes. We compared body morphology using geometric morphometrics and found substantial differences between habitats, although not all trends were consistent across size classes. The most striking aspects of divergence in small Nile perch were in mouth orientation, head size, and development of the caudal region. Medium‐sized Nile perch also showed differences in mouth orientation. Differences in large individuals were related to eye size and orientation, as well as caudal length. The observed patterns of divergence are consistent with functional morphological predictions for fish across divergent trophic regimes, high and low predation environments, and complex and simple habitats. Although this suggests adaptive divergence, the source of phenotypic variation is unknown and may reflect phenotypic plasticity and/or genetic differences. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 110 , 449–465.  相似文献   
55.
The United States is the sole superpower in the contemporary world and its role in the development of the law of the sea cannot be ignored. Although having not yet acceded to the U.N. Convention on the Law of the Sea, the United States has contributed to the development of the international law of the sea in numerous ways, including responding to the so-called excessive maritime claims in East Asia and creating new rules of maritime enforcement. This article assesses this recent U.S. practice.  相似文献   
56.
A survey was carried out between 2004 and 2005 in two ecologically different locations, Kakamega and Muhaka to assess diversity and abundance of wild host plants of lepidopteran stem borers as compared to maize plots during the cropping and non-cropping seasons. Kakamega in Western Kenya is characterized by a Guineo-Congolian rain forest mosaic and Muhaka at the Kenyan coast by a Zanzibar Inhambane mosaic with secondary grassy and woody vegetation. In Kakamega, wild host plants and maize covered 2 and 43% of the surveyed area. No variation in diversity and relative abundance of wild host plants was observed between both the cropping and non-cropping seasons. In Muhaka, the diversity and relative abundance of wild host plant species differed between seasons, with the Shannon Weaver Index (H) of 1.67 and 0.95 for cropping and non-cropping seasons, respectively. Similarly in this location, wild host plant cover varied between cropping (23%) and noncropping (17.9%). During both seasons, this was higher than the maize cover, with 10.7% and 0% for the cropping and non-cropping seasons, respectively. For both localities, the implication of the differences found in the abundance and diversity between the cropping and non-cropping seasons is discussed.  相似文献   
57.
The trichogrammatid Trichogramma bournieri Pintureau & Babault is a polyphagous parasitoid of eggs of several cereal stemborer species in eastern Africa. The effects of host species, host age and duration of host deprivation on the performance of the parasitoid were studied in the laboratory. Host acceptance and suitability were tested using five stemborer species. The noctuids Sesamia calamistis Hampson, Sesamia nonagrioides (Lefebvre), Busseola fusca (Fuller) the crambid Chilo partellus (Swinhoe) and the pyralid Eldana saccharina Walker were successfully parasitized by T. bournieri. Parasitism, number of progeny and developmental time varied significantly with host species. The eggs of S. calamistis and B. fusca were the most suitable, whereas those of E. saccharina were the least suitable. While parasitism and number of progeny tended to decrease with age of hosts, there were no significant differences in sex ratio. Longevity of the parasitoid increased with increase in deprivation of hosts from 0 to 12 days. Average lifetime fecundity per female decreased, indicating resorption of eggs.  相似文献   
58.
Xin Wang  Anthony D. Fox  Peihao Cong  Lei Cao 《Ibis》2013,155(3):576-592
More than 90% of the Lesser White‐fronted Geese Anser erythropus in the Eastern Palearctic flyway population winter at East Dongting Lake, China. To explain this restricted distribution and to understand better the winter feeding ecology and habitat requirements of this poorly known species, we assessed their food availability, diet and energy budgets at this site through two winters. Lesser White‐fronted Geese maintained a positive energy budget when feeding on above‐ground green production of Eleocharis and Alopecurus in recessional grasslands in autumn and spring to accumulate fat stores. Such food was severely depleted by late November and showed no growth in mid‐winter. Geese fed on more extensive old‐growth Carex sedge meadows in mid‐winter where they were in energy deficit and depleted endogenous fat stores. Geese failed to accumulate autumn fat stores in one year when high water levels prevented the Geese from using recessional grassland feeding areas. Fat stores remained lower throughout that winter and Geese left for breeding areas later in spring than in the previous year, perhaps reflecting the need to gain threshold fat stores for migration. Sedge meadows are widespread at other Yangtze River floodplain wetlands, but recessional grasslands are rare and perhaps restricted to parts of East Dongting Lake, which would explain the highly localized distribution of Lesser White‐fronted Geese in China and their heavy use of these habitats at this site. Sympathetic management of water tables is essential to maintain the recessional grasslands in the best condition for Geese. Regular depletion of fat stores whilst grazing sedge meadows in mid‐winter also underlines the need to protect the species from unnecessary anthropogenic disturbances that enhance energy expenditure. The specialized diet of the Lesser White‐fronted Goose may explain its highly restricted winter distribution and global rarity.  相似文献   
59.
记述了采自萨哈林岛1新种,Alopecosa mikhailovi sp.nov.,2♂♂,新种与solivaga种团近似.  相似文献   
60.
记述了在临夏盆地早中新世地层中发现的兰州巨獠犀(Aprotodon lanzhouensis)的下门齿化石,其特点为非常粗壮并强烈弯曲。新材料的发现使巨獠犀在临夏盆地的延续时代跨越渐新世/中新世界线的推测得到完全证实。巨獠犀分布的地质时代和地理范围与巨犀重合,但巨獠犀的化石地点和个体数量都相当稀少。巨獠犀的下颌形态功能特点指示其生活于晚始新世至早中新世中国西北、南亚和中亚干旱环境地带中镶嵌分布的少量近水环境。巨獠犀在中中新世之前彻底绝灭,其原因可能是气候变化的结果,也说明临夏盆地早中新世的环境特征与晚渐新世的疏林系统相似,而不同于中中新世的茂密森林。  相似文献   
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