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91.
周口店龙骨山新洞钙质沉积铀系年代 总被引:1,自引:1,他引:0
新洞(北京猿人遗址第4地点)钙质沉积地层厚2米。钙华的230Th/234U年龄为距今17.9万、13.9万、12.8万和8.8万年。新洞形成于距今20万年以前。洞内古人类开始活动时间为距今20万年以前,与猿人洞古人类活动时代上限(23-26万年)近似。 采自新洞的石钟乳和石笋样品,其生长年代为距今8-5万年。在七万多年时新洞古温度为13.2℃(石钟乳样)和13.7℃(石笋样)。至5.5万年左右,新洞地区古温度是11.9℃(石笋样)。 相似文献
92.
93.
Craig S. Feibel 《Evolutionary anthropology》1999,8(3):87-100
The fossiliferous and artifact-rich sites of East Africa, which are central to our understanding of early hominid evolution, also preserve a detailed record of explosive volcanism. The products of these eruptions, ash, lapilli, and pumice, are collectively known as tephra. They drifted down from the skies or washed down rivers in later rainy seasons, and now provide a key to both dating and correlation, and with them the establishment of a geologic framework for evolution. While some tephra can be directly dated, particularly through mineral phases they contain, the glass component of most ashes has a geochemical fingerprint that is unique to a particular eruption. That fingerprint defines an isochronous marker, a layer in time. By identifying characteristic geochemical signatures from far-flung localities, geologists can correlate sequences, establish relationships in time, and compile long-term records from local sections. Much of our understanding of the pattern and timing of Plio-Pleistocene evolution in East Africa is based on this tephrostratigraphic framework. © 1999 Wiley-Liss, Inc. 相似文献
94.
Giant tortoises spread to western Indian Ocean islands by sea drift in pre‐Holocene times,not by later human agency – response to Wilmé et al. (2016a) 下载免费PDF全文
Anthony S. Cheke Miguel Pedrono Roger Bour Atholl Anderson Christine Griffiths John B. Iverson Julian P. Hume Martin Walsh 《Journal of Biogeography》2017,44(6):1426-1429
Evidence from DNA phylogeny, Plio‐Pleistocene ocean currents, giant tortoise dispersal, evolution of plant defences, radiocarbon dates and archaeology indicates that the endemic giant tortoises on the Mascarenes and Seychelles colonized naturally and were not translocated there by humans. 相似文献
95.
Dated historical biogeography of the temperate Loliinae (Poaceae, Pooideae) grasses in the northern and southern hemispheres 总被引:1,自引:1,他引:0
Inda LA Segarra-Moragues JG Müller J Peterson PM Catalán P 《Molecular phylogenetics and evolution》2008,46(3):932-957
Divergence times and biogeographical analyses have been conducted within the Loliinae, one of the largest subtribes of temperate grasses. New sequence data from representatives of the almost unexplored New World, New Zealand, and Eastern Asian centres were added to those of the panMediterranean region and used to reconstruct the phylogeny of the group and to calculate the times of lineage-splitting using Bayesian approaches. The traditional separation between broad-leaved and fine-leaved Festuca species was still maintained, though several new broad-leaved lineages fell within the fine-leaved clade or were placed in an unsupported intermediate position. A strong biogeographical signal was detected for several Asian-American, American, Neozeylandic, and Macaronesian clades with different affinities to both the broad and the fine-leaved Festuca. Bayesian estimates of divergence and dispersal-vicariance analyses indicate that the broad-leaved and fine-leaved Loliinae likely originated in the Miocene (13My) in the panMediterranean-SW Asian region and then expanded towards C and E Asia from where they colonized the New World. Further expansions in America (10-3.8My) showed a predominant migratory route from North to South (N America<-->the Andes<-->Patagonia). This late Tertiary scenario of successive colonizations and secondary polyploid radiations in the southern hemisphere from the northern hemisphere was accompanied by occasional transcontinental long-distance dispersal events between South America and New Zealand. Multiple Pliocene dispersal events (3.6-2.5My) from the near SW European and NW African continents gave rise to the Macaronesian Loliinae flora, while a more recent Pleistocene origin (2-1My) is hypothesized for the high polyploid lineages that successfully colonized newly deglaciated areas in both hemispheres. 相似文献
96.
Determining the origin and age of the Westland beech (Nothofagus) gap, New Zealand, using fungus beetle genetics 总被引:1,自引:1,他引:0
The formation and maintenance of the Nothofagus beech gap in the South Island, New Zealand, has been the focus of biogeographical debate since the 1920s. We examine the historical process of gap formation by investigating the population genetics of fungus beetles: Brachynopus scutellaris (Staphylinidae) inhabits logs and is absent from the beech gap, and Hisparonia hystrix (Nitidulidae) is contiguous through the gap and is found commonly on sooty mould growing on several plant species. Both species show distinctive northern and southern haplotype distributions while H. hystrix recolonized the gap as shown by definitive mixing. B. scutellaris shows two major haplotype clades with strong geographical concordance, and unlike H. hystrix, has clearly defined lineages that can be partitioned for molecular dating. Based on coalescence dating methods, disjunct lineages of B. scutellaris indicate that the gap was formed less than 200 000 years ago. Phylogenetic imprints from both species reveal similar patterns of population divergence corresponding to recent glacial cycles, favouring a glacial explanation for the origin of the gap. Post-gap colonization by H. hystrix may have been facilitated by the spread of Leptospermum scoparium host trees to the area, and they may be better at dispersing than B. scutellaris which may be constrained by fungal host and/or microhabitat. The gap-excluded species B. scutellaris is found in both beech and podocarp-broadleaf forests flanking the Westland gap and its absence in the gap may be related to incomplete recolonization following glacial retreat. We also discuss species status and an ancient polymorphism within B. scutellaris . 相似文献
97.
Luiza Galbarczyk-Gąsiorowska Michał Gąsiorowski Krystyna Szeroczyńska 《Hydrobiologia》2009,631(1):173-183
Short sediment cores from two small oxbow lakes located in the Vistula valley near Warsaw (Poland) were analysed for chemical
composition and zooplankton (Cladocera) remains. The results of these analyses were evaluated using ordination techniques
and the results were used to reconstruct the history of human impact of the lakes. The cores were dated using the 210Pb method. These analyses show that the collected sediments (60 cm- and 67 cm-long-cores) were deposited during the last 150–200 years.
Cladocera assemblages were different in the two lakes; however, Bosmina longirostris was dominant among subfossil Cladocera species in both lakes. The presence of this species indicates the high trophic state
of the lakes. Changes in Cladocera species composition suggest that a significant increase in the lakes’ trophic levels has
occurred since the 1920s. The change could be related to the construction of flood dikes along the river Vistula, the isolation
of the studied lakes from the river, changes in land use, or some combination of these factors. The chemical composition of
sediments, particularly the increase in phosphorus and sulphur concentrations, confirms that the construction of dikes against
flood was the major factor inducing eutrophication of the oxbow lakes. This study shows that the Warsaw small water bodies
are especially sensitive to local disturbances caused by human activity, mainly water management, land use changes and agriculture.
Guest editors: K. Buczkó, J. Korponai, J. Padisák & S. W. Starratt
Palaeolimnological Proxies as Tools of Environmental Reconstruction in Fresh Water 相似文献
98.
F��lix Forest 《Annals of botany》2009,104(5):789-794
Background
Molecular dating has gained ever-increasing interest since the molecular clock hypothesis was proposed in the 1960s. Molecular dating provides detailed temporal frameworks for divergence events in phylogenetic trees, allowing diverse evolutionary questions to be addressed. The key aspect of the molecular clock hypothesis, namely that differences in DNA or protein sequence between two species are proportional to the time elapsed since they diverged, was soon shown to be untenable. Other approaches were proposed to take into account rate heterogeneity among lineages, but the calibration process, by which relative times are transformed into absolute ages, has received little attention until recently. New methods have now been proposed to resolve potential sources of error associated with the calibration of phylogenetic trees, particularly those involving use of the fossil record.Scope and Conclusions
The use of the fossil record as a source of independent information in the calibration process is the main focus of this paper; other sources of calibration information are also discussed. Particularly error-prone aspects of fossil calibration are identified, such as fossil dating, the phylogenetic placement of the fossil and the incompleteness of the fossil record. Methods proposed to tackle one or more of these potential error sources are discussed (e.g. fossil cross-validation, prior distribution of calibration points and confidence intervals on the fossil record). In conclusion, the fossil record remains the most reliable source of information for the calibration of phylogenetic trees, although associated assumptions and potential bias must be taken into account. 相似文献99.
Spiders, scorpions, mites and ticks (chelicerates) form one of the most diverse groups of arthropods on land, but their origin
and times of diversification are not yet established. We estimated, for the first time, the molecular divergence times for
these chelicerates using complete mitochondrial sequences from 25 taxa. All mitochondrial genes were evaluated individually
or after concatenation. Sequences belonging to three missing genes (ND3, 6, and tRNA-Asp) from three taxa, as well as the
faster-evolving ribosomal RNAs (12S and 16S), tRNAs, and the third base of each codon from 11 protein-coding genes (PCGs)
(COI-III, CYTB, ATP8, 6, ND1-2, 4L, and 4-5), were identified and removed. The remaining concatenated sequences from 11 PCGs
produced a completely resolved phylogenetic tree and confirmed that all chelicerates are monophyletic. Removing the third
base from each codon was essential to resolve the phylogeny, which allowed deep divergence times to be calculated using three
nodes calibrated with upper and lower priors. Our estimates indicate that the orders and classes of spiders, scorpions, mites,
and ticks diversified in the late Paleozoic, much earlier than previously reported from fossil date estimates. The divergence
time estimated for ticks suggests that their first land hosts could have been amphibians rather than reptiles. Using molecular
data, we separated the spider-scorpion clades and estimated their divergence times at 397 ± 23 million years ago. Algae, fungi,
plants, and animals, including insects, were well established on land when these chelicerates diversified. Future analyses,
involving mitochondrial sequences from additional chelicerate taxa and the inclusion of nuclear genes (or entire genomes)
will provide a more complete picture of the evolution of the Chelicerata, the second most abundant group of animals on earth.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
100.
Peter R. Teske Colin L. McLay Jonathan Sandoval-Castillo Isabelle Papadopoulos Brent K. Newman Charles L. Griffiths Christopher D. McQuaid Nigel P. Barker Gaetan Borgonie Luciano B. Beheregaray 《Molecular phylogenetics and evolution》2009,53(1):23-33
Crabs of the family Hymenosomatidae are common in coastal and shelf regions throughout much of the southern hemisphere. One of the genera in the family, Hymenosoma, is represented in Africa and the South Pacific (Australia and New Zealand). This distribution can be explained either by vicariance (presence of the genus on the Gondwanan supercontinent and divergence following its break-up) or more recent transoceanic dispersal from one region to the other. We tested these hypotheses by reconstructing phylogenetic relationships among the seven presently-accepted species in the genus, as well as examining their placement among other hymenosomatid crabs, using sequence data from two nuclear markers (Adenine Nucleotide Transporter [ANT] exon 2 and 18S rDNA) and three mitochondrial markers (COI, 12S and 16S rDNA). The five southern African representatives of the genus were recovered as a monophyletic lineage, and another southern African species, Neorhynchoplax bovis, was identified as their sister taxon. The two species of Hymenosoma from the South Pacific neither clustered with their African congeners, nor with each other, and should therefore both be placed into different genera. Molecular dating supports a post-Gondwanan origin of the Hymenosomatidae. While long-distance dispersal cannot be ruled out to explain the presence of the family Hymenosomatidae on the former Gondwanan land-masses and beyond, the evolutionary history of the African species of Hymenosoma indicates that a third means of speciation may be important in this group: gradual along-coast dispersal from tropical towards temperate regions, with range expansions into formerly inhospitable habitat during warm climatic phases, followed by adaptation and speciation during subsequent cooler phases. 相似文献