试论二叠纪牙形石古地理分区、演化及其控制因素

阐述二叠纪6个时期牙形石的分布及其古地理分区的划分和演变,探讨牙形石古地区分区的主控因素及其与古气候演变的关系,应用上述古地理分区模式恢复科迪勒拉山脉有关地体牙形石群落的古地理。     

Phylogeographic analysis of North American populations of the parasitic herbaceous plant Monotropa hypopitys L. reveals a complex history of range expansion from multiple late glacial refugia

Aim We carried out a phylogeographic study across the range of the herbaceous plant species Monotropa hypopitys L. in North America to determine whether its current disjunct distribution is due to recolonization from separate eastern and western refugia after the Last Glacial Maximum (LGM). Location North America: Pacific Northwest and north‐eastern USA/south‐eastern Canada. Methods Palaeodistribution modelling was carried out to determine suitable climatic regions for M. hypopitys at the LGM. We analysed between 155 and 176 individuals from 39 locations spanning the species’ entire range in North America. Sequence data were obtained for the chloroplast rps2 gene (n = 168) and for the nuclear ITS region (n = 158). Individuals were also genotyped for eight microsatellite loci (n = 176). Interpolation of diversity values was used to visualize the range‐wide distribution of genetic diversity for each of the three marker classes. Minimum spanning networks were constructed showing the relationships between the rps2 and ITS haplotypes, and the geographical distributions of these haplotypes were plotted. The numbers of genetic clusters based on the microsatellite data were estimated using Bayesian clustering approaches. Results The palaeodistribution modelling indicated suitable climate envelopes for M. hypopitys at the LGM in both the Pacific Northwest and south‐eastern USA. High levels of genetic diversity and endemic haplotypes were found in Oregon, the Alexander Archipelago, Wisconsin, and in the south‐eastern part of the species’ distribution range. Main conclusions Our results suggest a complex recolonization history for M. hypopitys in North America, involving persistence in separate eastern and western refugia. A generally high degree of congruence between the different marker classes analysed indicated the presence of multiple refugia, with at least two refugia in each area. In the west, putative refugia were identified in Oregon and the Alexander Archipelago, whereas eastern refugia may have been located in the southern part of the species’ current distribution, as well as in the ‘Driftless Area’. These findings are in contrast to a previous study on the related species Orthilia secunda, which has a similar disjunct distribution to M. hypopitys, but which appears to have recolonized solely from western refugia.     

The coastal-disjunct mesic flora in the inland Pacific Northwest of USA and Canada: refugia, dispersal and disequilibrium

Aim Understanding the history of the mesic‐adapted plant species of eastern British Columbia and northern Idaho, disjunct from their main coastal distribution, may suggest how biotas reorganize in the face of climate change and dispersal barriers. For different species, current evidence supports establishment of the disjunction via an inland glacial refugium, via recent dispersal from the coast, or via a combination of both. In this study, the modern distributions of the coastal‐disjunct vascular plants are analysed with respect to modern climate to examine how refugia and/or dispersal limitation control regional patterns in species richness. Location North‐west North America. Methods The distributions of nine tree and 58 understorey species with a coastal‐disjunct pattern were compiled on a 50‐km grid. The relationship between species richness and an estimate of available moisture was calculated separately for formerly glaciated and unglaciated portions of the coastal and inland regions. Growth habit and dispersal mode were assessed as possible explanatory variables for species distributions. Results Species richness shows a strong relationship to climate in coastal‐unglaciated areas but no relationship to climate in inland‐glaciated areas. In inland‐glaciated areas, richness is c. 70% lower than that expected from climate. Species with animal‐dispersed seeds occupy a larger portion of coastal and inland regions than species with less dispersal potential. Main conclusions Modern patterns of diversity are consistent with both refugia and dispersal processes in establishing the coastal‐disjunct pattern. The inland glacial refugium is marked by locally high diversity and several co‐distributed endemics. In the inland‐glaciated area, dispersal limitation has constrained diversity despite the nearby refugia. Onset of mesic climate within only the last 3000 years and the low dispersal capacity of many species in the refugium may explain this pattern. This study suggests that vascular plant species will face significant challenges responding to climate change on fragmented landscapes.     

Refugial persistence and postglacial recolonization of North America by the cold-tolerant herbaceous plant Orthilia secunda

Previous phylogeographical and palaeontological studies on the biota of northern North America have revealed a complex scenario of glacial survival in multiple refugia and differing patterns of postglacial recolonization. Many putative refugial regions have been proposed both north and south of the ice sheets for species during the Last Glacial Maximum, but the locations of many of these refugia remain a topic of great debate. In this study, we used a phylogeographical approach to elucidate the refugial and recolonization history of the herbaceous plant species Orthilia secunda in North America, which is found in disjunct areas in the west and east of the continent, most of which were either glaciated or lay close to the limits of the ice sheets. Analysis of 596 bp of the chloroplast trnS-trnG intergenic spacer and five microsatellite loci in 84 populations spanning the species' range in North America suggests that O. secunda persisted through the Last Glacial Maximum (LGM) in western refugia, even though palaeodistribution modelling indicated a suitable climate envelope across the entire south of the continent. The present distribution of the species has resulted from recolonization from refugia north and south of the ice sheets, most likely in Beringia or coastal regions of Alaska and British Columbia, the Washington/Oregon region in the northwest USA, and possibly from the region associated with the putative 'ice-free corridor' between the Laurentide and Cordilleran ice sheets. Our findings also highlight the importance of the Pacific Northwest as an important centre of intraspecific genetic diversity, owing to a combination of refugial persistence in the area and recolonization from other refugia.     

EARLY ORDOVICIAN (ARENIG) TRILOBITE PALAEOECOLOGY AND PALAEOBIOGEOGRAPHY OF THE SOUTH CHINA PLATE

Abstract:  Faunal composition of South Chinese Arenig benthic trilobite associations is investigated using the multivariate techniques of TWINSPAN, DCA and seriation. Eight fairly distinct benthic associations can be differentiated, organized primarily along a palaeobathymetrical gradient across the Yangtze Platform in southern Shaanxi and western Hubei and the Jiangnan Transitional Belt in northern Hunan: the Taihungshania , Neseuretus , Trinucleid and Asaphid- Pseudocalymene associations (shallow shelf), the Asaphid-Raphiophorid and Nileid-Asaphid associations (< 100 m outer shelf), the Nileid-Illaenid Association (deep outer shelf carbonates) and the Pseudopetigurus Association (deep outer shelf clastics). The highest levels of diversity are displayed by the Asaphid-Raphiophorid Association of western Hubei. Investigation of the biogeographical affinities of this fauna indicates that South China is biogeographically closest to the other Chinese geotectonic units, and displays strong faunal connections to other central and eastern Asian regions as well as to Tethyan and South American regions. Subdivision of the South Chinese trilobite fauna into different depth zones shows a statistically significant correlation between increasing water depth and increasing faunal cosmopolitanism, although taxa endemic to China or Gondwana also occur even in slope faunas. The results of this biogeographical analysis are consistent with a tropical or subtropical peri-Gondwanan association of South China with other Asian terranes.     

Plate tectonics and the distribution of cool temperate Southern Hemisphere macrolichens

GALLOWAY, D. J., 1988. Plate tectonics and the distribution of cool temperate Southern Hemisphere macrolichens. Several macrolichen genera in the families Lobariaceae and Pannariaceae speciate richly in cool temperate areas of the Southern Hemisphere between latitudes 35 and 55°S, being common in Nothofagus forests, subalpine shrubland, bog and grassland habitats. Affinities of southern cool temperate lichens are discussed in terms of plate tectonics and tectono-stratigraphic terranes.     

Tethyan uppermost Permian (Dzhulfian and Dorashamian) foraminiferal faunas and their paleogeographic and tectonic implications

The foraminiferal faunas and biostratigraphic correlation of the Tethyan uppermost Permian (Dzhulfian and Dorashamian) provide important paleogeographic and tectonic data for the interpretation of the Palaeofusulina-bearing terranes in East and Southeast Asia. These interpretations have a significant bearing on understanding Japanese pre-Cretaceous tectonostratigraphic and micropaleontologic data, as well as the geodynamic evolution of the Japanese Palaeofusulina-bearing terranes. The Tethyan foraminiferal fauna in the uppermost Permian is characterized by the occurrence of provincial and endemic schubertellid genera, and the absence of neoschwagerinids and verbeekinids which had characterized the rapidly evolving Middle Permian Tethyan marine faunas until their extinction at the end of the Midian. Difficulties in world-wide correlation of the uppermost Permian have resulted because of different geographic faunal compositions and the geographic patterns of extinction of Permian marine faunas. The Palaeofusulina fauna is one of the most reliable indicators of the uppermost Permian. Its presence or absence serves as paleogeographic constraints on East and Southeast Asian terranes. For example, the absence of Palaeofusulina fauna and the presence of late Midian Lepidolina multiseptata faunas in the Lhasa Terrane in Tibet and the Wolya Terrane in Sumatra (the third continental sliver north of Gondwana) are important, particularly, for identifying the rift–drift–collision process of the Gondwana-affinity terranes. They suggest a Late Permian separation of the two terranes from Gondwana. Tethyan Palaeofusulina occur in the latest Permian tropical to subtropical latitudinal belt and along with other geologic data assist in paleogeographic reconstructions and in interpreting the possible movement and emplacement of the Palaeofusulina-bearing terranes such as the Maizuru, South Kitakami–Kurosegawa and Chichibu terranes in Japan. They reveal that: (1) the Upper Permian Maizuru Group was deposited on the eastern continental margin of South China; (2) the occurrence of the Lower Permian Cathaysian flora and a number of geologic data in the South Kitakami–Kurosegawa suggest an arc–trench system setting and the Late Permian deposition in a shallow open-marine environment in proximity to South China; (3) foraminiferal biogeograpic data and the reconstructed oceanic plate stratigraphy in the Chichibu Terrane constrain the location of the Chichibu Seamount Chains to the western part of the Panthalassan domain, as they moved westwards against the Cathaysian Continent until their Jurassic accretion.     

Timing,exotic terranes,angiosperm diversification,and panbiogeography

Abstract

The relationships between panbiogeography, geology, and systematics are discussed against a historical perspective of biogeography. Recent refinements of the panbiogeographic method are welcomed, but it is emphasised that the most important requirements in application of the panbiogeographic method, as in all biogeographic analysis, are freedom from prior bias and objectivity of judgement The times of major phases in angiosperm diversification are determined for the Early Cretaceous (primarily by the Potomac Group megaflora/palynoflora sequence), and subsequent phases occurring in the Late Cretaceous and the Tertiary (principally by the global pollen record). This dating of events in angiosperm evolution permits the following conclusions: the disintegration of Pacifica, according to the scheme of Nur & Ben-Avraham, would occur too soon to have any relevance for angiosperm biogeography; the dissolution of Gondwana occurred too early to explain disjunct distributions in the more recently evolved angiosperm groups, e.g., Compositae; long-distance drift of exotic terranes is not likely to have much relevance for angiosperm biogeography; and Owen’s scenario of continental drift on an expanding earth may well provide a solution to the problem of migration between north and south hemisphere temperate floras in the Early and Mid-Cretaceous. Aspects of the biogeography of Nothofagus are discussed in the context of some of the other points raised.     

New Zealand tectonostratigraphic terranes and panbiogeography

Abstract

Tectonostratigraphic terranes of New Zealand, grouped for purposes of the present discussion into six groups, are briefly reviewed as to their role in the biogeographic evolution of the present day biota of New Zealand. Of all the terranes so far recognised, only the Torlesse (Rakaia) terrane is thought to have originated outside the New Zealand region; of the various models proposed to explain its origin and emplacement, only that by McKinnon (1983) would allow it to have acted as a “raft” that could have transported a biota en masse. The former existence of a “lost continent” (Pacifica), suggested as apossible source for Torlesse sediments, is regarded as improbable. The long time (at least 140 Ma, and probably 190 Ma) since terrane accretion, and the extreme degree of geological (and geographical) complexity and change that New Zealand has undergone since accretion, make it most improbable that the present day distribution of plants and animals among the terranes reflects the original distribution of their ancestors.     

Refugia in the Cordilleran ice sheet of western North America: chloroplast DNA diversity in the Arctic–alpine plant Oxyria digyna

Aim  Late Pleistocene ice sheets are thought to have covered most of western Canada, including all of British Columbia (BC). We examine patterns of genetic variation in an Arctic–alpine plant to evaluate the possibility of full glacial refugia within the area covered by the Cordilleran ice sheet (CIS) and to uncover post-glacial migration routes.
Location  Western North America.
Methods  We sampled 1030 individuals of the Arctic–alpine plant Oxyria digyna from 117 populations distributed over much of its range in western and northern North America. DNA haplotypes were identified using restriction site analysis of two chloroplast DNA intergene spacer regions, psb A- trn H and trn T-L. We examined the geographical distribution of haplotype diversity in relation to latitude, and also compared various indices of diversity in putatively glaciated and unglaciated regions. Patterns of migration were inferred using nested clade analysis.
Results  We detected a total of 20 haplotypes. High haplotype diversity was found in Beringia, in unglaciated western USA, and in northern BC at 57–59° N, well within the accepted limits of the CIS. Ancestral haplotypes were also centred in northern BC.
Main conclusions  High genetic diversity of Oxyria digyna is expected in unglaciated regions, but unexpected in northern BC if British Columbia was entirely covered by ice during the late Pleistocene. Our observations suggest the presence of unglaciated areas providing late Pleistocene refugia in northern BC. Such refugia would have important implications for the origins and migrations of many plant and animal species in north-western North America.