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541.
Water management in Uzbekistan (Central Asia) is facing tremendous challenges. They are rooted in past and present environmental degradation, the socio-economic transition after the breakup of the Soviet Union, and the impacts of climate change. The Uzbek government has initiated reforms in the agricultural and water sectors to steer the socio-economic transition and address the threats of increasing water scarcity and decreasing agricultural productivity. However, despite the urgency of the problems and massive international assistance changes to the water management regime have only been minimal so far. In this paper we identify major structural barriers for adaptation of the water management regime through an analysis of two recent policy processes. Both processes address pressing water management issues such as “coping with extreme events” and “providing water for ecosystems”. They were analyzed using the Management and Transition Framework as well as a group model building exercises with stakeholders on the national, regional and local levels. The analyses reveal a lack of vertical integration across administrative levels of the formal system and a still prevailing strong centralization of water management. Moreover the water management regime is strongly influenced by informal institutions that shape the outcomes of policy processes. The interactions guided by informal institutions provide an informal link between different administrative levels of the regime. However, those informal networks and the social capital embedded in them rather prevent needed changes. The resulting combination of top down institutional change initiated by socio-economic transition and bottom-up consolidation of the existing status quo via informal processes and networks prevents social learning. It also slows down an adaptation process that potentially could lead to a transition towards a more adaptive regime. 相似文献
542.
Although Asia is thought to have played a critical role in the radiation of artiodactyls, the fossil record of stem selenodonts
(“dichobunoids”) remains dramatically poor in tropical Asian regions. In this study, we report a new dichobunid genus and
species Cadutherium kyaukmagyii and a new basal ruminant genus and species Irrawadymeryx pondaungi, from the late Middle Eocene Pondaung Formation, Central Myanmar. Although the scarcity of the present material prevents
any attempts to investigate the phylogenetic relationships of Cadutherium with contemporaneous forms from other Holarctic landmasses, this new form shed new light on the diversity of these small
rabbit-like ungulates during a key period of their evolutionary history. Reexamination of the small-bodied artiodactyls from
Pondaung leads us to propose new identifications of certain published specimens and, in turn, to investigate the temporal
and geographic distribution of taxa recognized in the Pondaung Formation. Although fragmentary, these potential new taxa reveal
an unsuspected diversity of small forms among artiodactyls of Pondaung. This addition to the Eocene record of dichobunoids
and early ruminants provides further insight in the diversity of dental patterns among small artiodactyls from the Pondaung
Formation and attests to the antiquity of these groups in Southeast Asia. 相似文献
543.
544.
545.
Foraging desert ants, Cataglyphis fortis, encounter different sequences of visual landmarks while navigating by path integration. This paper explores the question whether the storage of landmark information depends on the context in which the landmarks are learned during an ant's foraging journey. Two experimental set-ups were designed in which the ants experienced an artificial landmark panorama that was placed either around the nest entrance (nest marks) or along the vector route leading straight towards the feeder (route marks). The two training paradigms resulted in pronounced differences in the storage characteristics of the acquired landmark information: memory traces of nest marks were much more robust against extinction and/or suppression than those of route marks. In functional terms, this result is in accord with the observation that desert ants encounter new route marks during every foraging run but always pass the same landmarks when approaching the nest entrance. 相似文献
546.
Intergeneric transmission of a marine plant DNA virus 总被引:1,自引:0,他引:1
D. G. Müller 《Die Naturwissenschaften》1992,79(1):37-39
547.
548.
Roland Axt-Fliedner Andrii Kurkevych Maciej Slodki Maria Respondek-Liberska Katarzyna Zych-Krekora Rüdiger Stressig Jochen Ritgen Guiseppe Rizzo Martin Krapp Luc de Catte Gunther Mielke Stephan Bosselmann Mathias Meyer-Wittkopf Andreea Kawecki Aline Wolter Marios Mamalis Christian Enzensberger 《黑龙江环境通报》2017,37(8):812-819
549.
A new assemblage of basal dichobunoid artiodactyls from the middle-Eocene Shanghuang fissure fillings includes the diacodexeid
Jiangsudon shanghuangensis gen. and sp. nov., a new species of the lantianine dichobunoid Elaschitotherium, Elaschitotherium crepaturus sp. nov., and an indeterminate suoid which is presently the earliest record of this clade. Diacodexeids are also represented
by two forms provisionally referred to cf. Diacodexis sp. and to an indeterminate Diacodexeidae, respectively. The occurrence of diacodexeids in Shanghuang contrasts with the
early and earliest middle-Eocene chronological range of the family in Europe and North America and suggests that the stratigraphic
range of the family in Asia extends up to the middle Eocene. This may reflect particular habitats in coastal China that may
have been relatively stable during the early and middle Eocene, thus preserving forest-dwelling artiodactyls that became extinct
in the other Holarctic regions. Compared to other supposedly coeval North American, European, and Asian faunas, the Shanghuang
mammalian assemblage is most similar to early Uintan faunas of North America but is also remarkable in recording forms close
to taxa that are characteristic of the Wasatchian and Bridgerian North American Land Mammal Ages. The Irdinmanhan age of the
Shanghuang fauna is supported by the mammalian assemblage recovered from the fissure D, but an Arshantan age cannot be completely
ruled out at this point. Although the Shanghuang assemblage is biased towards preservation of small components of the mammalian
fauna, the Shanghuang fauna provide an important and unique window into the Eocene diversity and early evolution of cetartiodactyls
in eastern Asia. 相似文献
550.
Palaeospinacids are a group of basal galeomorph sharks and are placed in the order Synechodontiformes (Chondrichthyes, Neoselachii) ranging from the Permian to the Eocene. Currently, there is a controversy concerning the identity of diagnostic characters for distinguishing palaeospinacid genera because of very similar dental morphologies and the scarcity of articulated skeletal material. The most notable character for distinguishing species within the Palaeospinacidae is, however, the dental morphology. The main dental character uniting all palaeospinacids is the very specialised pseudopolyaulacorhize root vascularisation. A re-examination of articulated neoselachian skeletons from the Lower Jurassic of Lyme Regis (England) and Holzmaden (S Germany), and recently discovered specimens from the Upper Jurassic of the Solnhofen area and Nusplingen (S Germany) has yielded several hitherto unrecognised complete skeletons of the palaeospinacids Synechodus and Paraorthacodus enabling a re-evaluation of characters. These specimens indicate that the number of dorsal fins and the presence or absence of dorsal fin spines represent important features for identifying palaeospinacids. Synechodus bears two dorsal fins without fin spines, whereas Paraorthacodus only has a single dorsal fin lacking a fin spine directly in front of the caudal fin. All palaeospinacids from the Early Jurassic have two spines supporting the dorsal fins and are consequently assigned to a new genus, Palidiplospinax nov. gen. Three species are placed into the new taxon: Synechodus enniskilleni, S. occultidens and S. smithwoodwardi. 相似文献