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1.
On the basis of taxonomic, ecological and geological data, a hypothesis is presented on the trends of evolutionary radiation of the Tonkin leafmonkey (Presbytis francoisi). The ancestral form was mainly black likeP. f. hatinhensis and located in the limestone hilly regions of Northern Annam. The range expanded at the end of the upper Pleistocene, and subspeciation occurred at the beginning of the recent epoch (about 9000 years ago). The direction of evolution of this leafmonkey was northeastwards, and the trend of colour change was the progressive whitening of the black body adapted to the more or less denuded rocky substrate.  相似文献   

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Tropical rain forest expansion and savanna woody vegetation thickening appear to be a global trend, but there remains uncertainty about whether there is a common set of global drivers. Using geographic information techniques, we analyzed aerial photography of five areas in the humid tropics of northeastern Queensland, Australia, taken in the 1950s and 2008, to determine if changes in rain forest extent match those reported for the Australian monsoon tropics using similar techniques. Mapping of the 1950s aerial photography showed that of the combined study area (64,430 ha), 63% was classified as eucalypt forests/woodland and 37% as rain forest. Our mapping revealed that although most boundaries remained stable, there was a net increase of 732 ha of the original rain forest area over the study period, and negligible conversion of rain forest to eucalypt forest/woodland. Statistical modeling, controlling for spatial autocorrelation, indicated distance from preexisting rain forest as the strongest determinant of rain forest expansion. Margin extension had a mean rate across the five sites of 0.6 m per decade. Expansion was greater in tall open forest types but also occurred in shorter, more flammable woodland vegetation types. No correlations were detected with other local variables (aspect, elevation, geology, topography, drainage). Using a geographically weighted mean rate of rain forest margin extension across the whole region, we predict that over 25% of tall open forest (a forest type of high conservation significance) would still remain after 2000 years of rain forest expansion. This slow replacement is due to the convoluted nature of the rain forest boundary and the irregular shape of the tall open forest patches. Our analyses point to the increased concentration of atmospheric CO(2) as the most likely global driver of indiscriminate rain forest expansion occurring in northeastern Australia, by increasing tree growth and thereby overriding the effects of fire disturbance.  相似文献   

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Asthma prevalence has increased over the last fifty years, but the more recent changes have not been conclusively determined. Studies in children indicate that a plateau in the prevalence of asthma may have been reached, but this has not yet been confirmed in adults. Epidemiological studies have suggested that the prevalence of asthma in adults is approximately 7-10% in different parts of the western world.We have now performed a large-scale epidemiological evaluation of the prevalence of asthma and respiratory symptoms in adults between the ages of 16-75 in West Sweden. Thirty thousand randomly chosen individuals were sent a detailed questionnaire focusing on asthma and respiratory symptoms, as well possible risk factors. Sixty-two percent of the contacted individuals responded to the questionnaire. Asthma prevalence, defined as asthma diagnosed by a physician, was 8.3%. Moreover, the prevalence of respiratory symptoms was lower compared to previous studies. The most common respiratory symptom was any wheeze (16.6%) followed by sputum production (13.3%). In comparison with studies performed 18 years ago, the prevalence of asthma has not increased, and the prevalence of most respiratory symptoms has decreased. Therefore, our data argues that the continued increase in asthma prevalence that has been observed over the last half century is over.  相似文献   

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Decadal‐ to multi‐decadal variations have been reported in many regional ecosystems in the North Pacific, resulting in an increasing demand to elucidate the link between long‐term climatic forcing and marine ecosystems. We detected phenological and quantitative changes in the copepod community in response to the decadal climatic variation in the western subarctic North Pacific by analyzing the extensive zooplankton collection taken since the 1950s, the Odate Collection. Copepod species were classified into five seasonal groups depending on the timing of the annual peak in abundance. The abundance of the spring community gradually increased for the period 1960–2002. The spring–summer community also showed an increasing trend in May, but a decadal oscillation pattern of quasi‐30‐year cycles in July. Phenological changes coincided with the climate regime shift in the mid‐1970s, indicated by the Pacific decadal oscillation index (PDO). After the regime shift, the timing of the peak abundance was delayed one month, from March–April to April–May, in the spring community, whereas it peaked earlier, from June–July to May–June, in the spring–summer community, resulting in an overlap of the high productivity period for the two communities in May. Wintertime cooling, followed by rapid summertime warming, was considered to be responsible for delayed initiation and early termination of the productive season after the mid‐1970s. Another phenological shift, quite different from the previous decade, was observed in the mid‐1990s, when warm winters followed by cool summers lengthened the productive season. The results suggest that climatic forcing with different decadal cycles may operate independently during winter–spring and spring–summer to create seasonal and interannual variations in hydrographic conditions; thus, combinations of these seasonal processes may determine the annual biological productivity.  相似文献   

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An abundant fossil record of the snake clade Scolecophidia exists in Europe; however, the minute snake is noticeably absent in reports about the North American Paleogene and Neogene. Presented here are four localities from Florida, USA, that contain scolecophidian remains older than the Pleistocene: Thomas Farm (late Early Miocene, Hemingfordian Land Mammal Age, LMA), Live Oak (Oligocene-Miocene transition, latest Arikareean LMA), White Springs 3B (late Arikareean LMA), and Brooksville 2 (Late Oligocene, middle Arikareean LMA). These remains extend their known existence by about 26 m.y. and are now the oldest reported scolecophidian remains in North America. Molecular evidence on extant scolecophidians concludes that these tiny snakes have a Gondwanan origin. Interestingly, the oldest record of a scolecophidian is from Europe (Belgium) and dates back to the middle Paleocene (MP 1–5). The earliest African record of the snake clade comes from the Paleocene-Eocene boundary in Morocco. The clade is apparently absent from Europe and Middle East deposits dating from the latest Eocene through to the latest Oligocene (MP 19–30) and to the Early Miocene (MN 4). A portion of this time is known as the booid ‘Dark Period’ which represents an apparent response to global aridization and cooling. Scolecophidians appear to re-emerge into the southern Eurasian record in the Early Miocene (MN 4) and become widely dispersed throughout Europe and Middle East. The fossil record of these minute snakes is largely absent in southern Asia and South America. It is possible that the current lack of a decent fossil scolecophidian record outside of Europe and Middle East is due mainly to a bias in the methodology to recover fossils; wet sieving sediments through < 1.0 mm mesh is needed to recover the minuscule vertebrae.  相似文献   

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Synopsis The interrelationships of 31 actinistian species (including Latimeria chalumnae) are analyzed based on a cladistic analysis of 75 osteological characters. Inference of evolutionary trends (e.g., modification of body shape and skull morphology) from the phylogenetic patterns demonstrates that the morphology of actinistians is less conservative than has been proposed previously. This empirical cladistic approach supports two distinct tempos of evolution during an evolutionary history of 380 million years. Along a phylogenetic pathway originating with a Devonian stem-species and ending with the living Latimeria chalumnae (including 101 morphological changes and 18 cladogenetic events), the first tempo occurred during the Devonian — Permian periods as a decreasing rate of morphological changes, which was followed by a stabilizing tempo during the Permian — Recent periods. The decreasing tempo is characterized by a sequence of gradual versus quantum temporal changes and low versus faster rates, whereas the stabilizing tempo primarily is gradual and low. In contrast to a common assumption, no significant correlation was found between the rates of morphological evolution and the temporal diversity of species.  相似文献   

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The revolution in molecular biology that began nearly 50 years ago has had an enormous impact in the lab, but it also triggered a quieter revolution in undergraduate teaching. How has it affected the content and teaching methodology of undergraduate courses, and is the training that students now receive in the molecular life sciences appropriate to their future career paths?  相似文献   

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An overview of the upper Oligocene-upper Miocene marine sediments outcropping in the Maltese Islands provides a detailed stratigraphical setting of several marine mammal assemblages. The studied fossil material collected within the entire sequence, is now kept in the National Museum of Natural History of Mdina (Malta). Nannoplankton analysis of some selected sections, where mammal remains have been discovered, is also undertaken. The fossil marine mammals, consisting mostly of isolated ear bones and teeth, are referred to cetaceans (both mysticetes and odontocetes), sirenians, and pinnipeds. The cetacean record evidences an evolutionary pattern that agrees with the Oligo-Miocene general trend, characterized by the progressive rarefaction and disappearance of archaic families (squalodontids, waipatiids, and, maybe, mammalodontids), and by the appearance and diversification of the extant families represented within younger strata (kogiids, pontoporiids and ziphiids). Pontoporiids, waipatiids, and tentatively mammalodontids are here reported for the first time in the Mediterranean, while the kogiid record represents the only sure Miocene evidence of this family in the Mediterranean. The geographical distribution of the mammalodontids and the waipatiids, based on the Maltese and extra-Mediterranean records, supports an open communication between the Proto-Mediterranean and the Indo-Pacific during the late Oligocene. Sirenians are represented by several dugongid pachyosteosclerotic rib fragments, collected from upper Oligocene through upper Miocene sediments. Pinnipeds are represented by a femur fragment from the Serravallian, referred to an indeterminate monachine, a phocid subfamily already reported from the Mio-Pliocene of the Mediterranean.  相似文献   

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The second half of the 20th century has witnessed the birth and growth of biological ultrastructure research--a branch of cell biology in which electron microscopy plays an important role. After a humble start in around 1950, when only a limited arsenal of instrumentation was available, a wealth of auxiliary methodologies were developed and gradually put in use. Here we review these techniques: ultramicrotomy of "optimally" fixed and prepared samples, histochemical methods such as immuno-electron microscopy and electron microscope autoradiography, negative staining techniques, freeze-fracturing and other techniques. Closer to the millennium shift, various cryotechniques have gradually developed. Together with computer-based reconstruction methods they are likely to play increasingly more important roles in the future.  相似文献   

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我国柑桔害虫的研究现状   总被引:3,自引:0,他引:3  
赵志模 《昆虫知识》2000,37(2):110-116
柑桔是我国南方最重要的果树之一。改革开放以来,柑桔生产的迅速发展对繁荣农村经济,增加农民收入,满足城乡人民的生活需求发挥了重要作用。据国家统计局发表的资料,1998年全国柑桔种植面积发展到127万hmz,总产量达85.9亿kg。但由于柑桔属多年生常绿果树,原产于中国,种植地区气候温和,雨量充沛,因此在柑桔生长发育过程中遭受多种害虫为害。据忡国果树病虫志》(第二版户已载,我国柑桔害虫有2门14目106科865种。在这些害虫中不少属于客居性或偶然发生、为害很轻的种类;有的属于与其他果树或作物共有的种类;只有一部分属柑桔的主…  相似文献   

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A distal tibia, YGSP 1656, from the early Late Miocene portion of the Chinji Formation in Pakistan is described. The fossil is 11.4 million years old and is one of only six postcranial elements now assigned to Sivapithecus indicus. Aspects of the articular surface are cercopithecoid-like, suggesting some pronograde locomotor activities. However, YGSP 1656 possesses an anteroposteriorly compressed metaphysis and a mediolaterally thick medial malleolus, ape-like features functionally related to orthograde body postures and vertical climbing. YGSP 1656 lacks specializations found in the ankle of terrestrial cercopithecoids and thus Sivapithecus may have been primarily arboreal. Nevertheless, the morphology of this tibia is unique, consistent with other interpretations of Sivapithecus postcranial functional morphology that suggest the locomotion of this ape lacks a modern analog. Based on the limited postcranial remains from S. indicus, we hypothesize that this taxon exhibited substantial body size dimorphism.  相似文献   

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We describe phalanges of the KNM-BG 35250 Nacholapithecus kerioi skeleton from the Middle Miocene of Kenya. Phalanges of N. kerioi display similarities to those of Proconsul heseloni despite their enhanced robusticity. They do not show highly specialized features as in living suspensory primates. However, N. kerioi manifests several distinctive features that are observed in neither living arboreal quadrupeds nor P. heseloni or P. nyanzae. The most remarkable of them is its phalangeal elongation. N. kerioi phalanges (particularly pedal) are as long as those of Pan despite its much smaller body size. While lengthened digits enable a secure grip of supports and are especially adaptive for grasping large vertical trunks, the skeletal and soft tissues are subjected to greater stress. Probably, strong selective pressures favored powerful hallucal/pollical assisted grips. Although this functional adaptation does not exclude the possible use of the terrestrial environment, arboreal behavioral modes must have been crucial in its positional repertoire. N. kerioi is distinguished from P. heseloni in the greater size of its manual phalanges over its pedal phalanges. These derived features of N. kerioi suggest positional modes supporting more weight on the forelimb, and which occur more frequently on vertical supports. If Proconsul is referred to as an "above-branch arboreal quadruped" with a deliberate and effective climbing capability, N. kerioi may be thought of as an "orthograde climber". While living apes are powerful orthograde climbers, they are also more or less suspensory specialists. Suspensory behavior (plus climbing) and pronograde quadrupedalism (plus climbing) are the two main arboreal behavioral adaptations in living anthropoids. Thus, N. kerioi is an unusual fossil primate in that it cannot be incorporated into this dichotomy. It is plausible that a N. kerioi-like orthograde climber with large forelimbs and cheiridia was a precursor of suspensory living apes, and N. kerioi may demonstrate what an initial hominoid of this grade might have looked like.  相似文献   

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High-resolution palaeoenvironmental changes, corresponding to a mean time interval of 450 years covering the last 48,000 years, were examined in a core from the Cretan Basin in the southern Aegean Sea. The intensity and duration of the climatic and oceanographic events were determined by examining the compositional changes in the planktonic foraminifera and pollen assemblages, along with the δ18O signal of Globigerinoides ruber. A reconstruction of sea-surface temperatures was attempted using the Modern Analogue Technique (MAT). In total, 10 stadials and 6 interstadials occurred over the last 48,000 years. These fluctuations in climatic conditions coincide with fluctuations documented in the western and central Mediterranean and seem to be associated with Dansgaard–Oeschger events. Some of these climatic fluctuations are correlated with changes in the vegetation in the surrounding land.

Between 48 and 10 cal kyr BP the most pronounced stadials occurred at 41 cal kyr BP (C69-ST10) and at 13 cal kyr BP (C69-ST4). These events are characterized by: (i) high positive δ18O values of Globigerinoides ruber, (ii) drops in SST and (iii) increases in aridity. These events may be correlated with the Heinrich H4 event and the Younger Dryas event, respectively. Two other stadials at 23 cal kyr BP (C69-ST6) and at 16 cal kyr BP (C69-ST5) which are characterized by increases in the abundance of the cold plaktonic foraminifera species and increases in aridity may be correlated with the H2 and H1 events, respectively. The dominant planktonic foraminiferal species during the stadials witch are correlated with the Heinrich events were Turborotalita quinqueloba and Globorotalia scitula. The most pronounced interstadials occurred between 39.5 and 38.5 cal kyr BP (C69-IST6) and between 25 and 24 cal kyr BP (C69-IST3) and are characterized by depletion in δ18O values, increases in SST and increases in humidity. The former event coincides with the formation of the sapropelitic layer S2.

In the Holocene the most pronounced stadial occurred between 8 and 6.5 cal kyr BP (C69-ST2), during the interruption of S1 and is characterized by a reduction in SST and an increase in aridity. The most pronounced interstadials of Holocene occurred during the formation of S1a and S1b between 9 and 8 cal kyr BP (C69-IST1) and between 6.5 and 5.5 cal kyr BP (C69-IST2), respectively. These events are characterized by depletion in δ18O values, increased SST and an increase in humidity as is indicated by the expansion of temperate evergreen and Mediterranean taxa in the pollen record.  相似文献   


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This paper summarises the development, over the last15 years, of the rearing techniques of the two mostimportant finfish cultivated in France: the sea bass,Dicentrarchus labrax and the sea bream, Sparus auratus.The historical background and the main achievementsthat led to the present industrial production levelare summarised i.e. control of environmentalfactors, intensification of rearing densities, simplification and improvement of feeding sequences,resolution of the main skeletal deformities,utilisation of closed recirculating systems, etc...The new research orientations that are presentlyinvestigated to continue the promotion of marine fishfarming in France are also discussed.  相似文献   

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A strong correlation is observed between an El Niño index (anomalies in tropical Pacific sea surface temperature) and rainfall in the Judean foothills near Jerusalem over the past 20 years. These relationships clearly influenced the growth of local pine trees, as reflected in the width of their annual tree rings. The ability to predict El Niño events about a year in advance lend a special significance to relationships reported here for ecology, agriculture and water management in this climatic transition zone. To help explain the observed, long-range teleconnection we propose a possible mechanism based on a newly identified direct cloud connection between equatorial Africa (more directly affected by El Niño) and the Southeastern Mediterranean shoreland. The penetration and contribution of the moisture current from equatorial Africa to this region may depend on a shift in the usual rain generating moisture currents to southwesterly trajectories (passing over north Africa). The occurrence of such shifts is supported by the observed decrease in the mean 18O content of the local precipitation during El Nino winters.  相似文献   

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