ISSN:0040-0262    

DOI:10.1002/j.1996-8175.1988.tb04532.x

出版商:Wiley    

年代:2019

数据来源: WILEY

摘要:

SummaryHistorical geological and historical floristic/vegetational data show an extraordinary dynamic world. Moving plates, the upheaval of mountain chains, and changes of climate and vegetation are the main elements of this dynamism. They are partly endogene, resulting from forces inside the earth, and partly exogene, resulting from direct or indirect changes of solar radiation received by the earth. The evolution and differentiation of the tropical floras and the migration of floristic elements is heavily influenced by these factors. The glacial‐interglacial climatic cycles of the last few million years had an especially profound effect on the biosphere, including the tropics. There were profound changes in vegetation, not only displacement of zones or belts, but also reordering of species, and the formation and disappearance of refugia in lowlands and mountains.

ISSN:0040-0262    

DOI:10.2307/1221096

出版商:Wiley    

年代:2019

数据来源: WILEY

摘要:

SummaryAn analysis is made of the growth rate of tropical herbaria and only a few areas, Central America, Pacifica and the West Indies appear to have adequate collecting rates. In spite of recent calls for accelerated collecting in the tropics, the overall rates have not increased greatly even though the threat of destruction of natural habitats and species loss is an increasingly serious problem. Some key areas in greatest need of tropical Holistic inventory in the near future are suggested. In the Neotropics, Atlantic coastal Brazil, the Colombian, Chocó, Bolivia, Rondônia and Acre in Brazil, and Guyana stand out as in need of further inventory. The collections of Chrysobalanaceae between 1972 and 1986 are analyzed and although many new species have been found, a large amount of material of common species has been repeatedly re‐collected, collections of both Chrysobalanaceae and the Projeto Flora Amazonica program are still yielding at least one new species per every 100 numbers collected, indicating continued inadequate inventory of the Neotropics. Tropical flora programs are discussed and it is suggested that there is a need for many more florulas of carefully selected small areas of the tropics. An analysis of the productivity ofFlora Neotropicashows that in order to provide an adequate monographic basis for local floras there is an urgent need to increase the rate of production of monographs of tropical groups. This survey indicated that the work force in systematic botany is far too small for the urgent tasks that face it over the next few years.

ISSN:0040-0262    

DOI:10.2307/1221097

出版商:Wiley    

年代:2019

数据来源: WILEY

摘要:

SummaryOf the roughly 265,000 species of plants in the world, about a third occur in temperate regions, a third in Latin America, and a third in the tropics and subtropics of Africa and Asia. Tropical forests are being destroyed very rapidly, as a result of the explosive growth of a record human population, extensive poverty, and an unwillingness to learn about and practice sustainable land use in the tropics. As a consequence, at least a fifth of the total plant species in the world, something on the order of 60,000 species, are threatened with extinction over the next several decades. Systematic botanists need urgently to devise comprehensive plans to inventory plant diversity, especially in the tropics. They should play a major role in making possible the utilization of this diversity for human benefit, and in conserving as extensive a sample as possible.

ISSN:0040-0262    

DOI:10.2307/1221098

出版商:Wiley    

年代:2019

数据来源: WILEY

摘要:

SummaryAn overview of botanical exploration as related to plant distribution patterns in Colombia is presented. Reference is made to current efforts to study the natural vegetation, and the need for intensive work in many areas of the country is emphasized.

ISSN:0040-0262    

DOI:10.2307/1221099

出版商:Wiley    

年代:2019

数据来源: WILEY

摘要:

SummaryEcuador covers some 300,000 km2on the west coast of the South American continent. The country is divided into three natural regions: the coastal plain, the Andes cordillera, and the eastern lowlands. Twenty‐six life zones, including deserts, rainforests, and high montane vegetation types, are represented in the country. The flora includes an estimated 20,000 species of vascular plants. In this study the distribution of a sample of 536 species is analyzed, and some conspicuous phytogeographic patterns are obvious. The lowland flora is rich in widespread species and many of them occur on both sides of the Andes. The coastal plain is rich and the eastern lowlands are poor in endemics. The mid‐elevations between 900 m and 3000 m house about half of the species of the country although they constitute only 10% of the area. Endemism is high at mid‐elevations: 39% of the mid‐elevation species do not reach beyond Ecuador. Especially the western slopes of the Andes are rich in endemics with 10% of the total Ecuadorean flora being restricted to them. The Ecuadorean highlands above 3000 m house 10% of the total flora of the country. Endemism in the highlands is about the same as at mid‐elevations.

ISSN:0040-0262    

DOI:10.2307/1221100

出版商:Wiley    

年代:2019

数据来源: WILEY

摘要:

SummaryIn a brief introduction to the Guianan area (location, geomorphology and climate), the author gives a short description of the main forest types occurring in the Guianas: upland moist forest, montane and lower montane forest, inundated forests, transition forests, and forests on white sand soils. Then, the distribution patterns of selected plant groups represented in the Guianan lowland forest region (Meliaceae, Caryocaraceae, Tabernaemontanoideae, Musaceae, Zingiberaceae, Arecaceae, Passifloraceae,Lindsaea,Ochnaceae) are analyzed. The endemism and floristic affinities of the Guianan forests are briefly discussed in relation to the theory of the South American forest refugia.

ISSN:0040-0262    

DOI:10.2307/1221101

出版商:Wiley    

年代:2019

数据来源: WILEY

摘要:

SummaryDuring the last 40 years, an impressive amount of biological, especially botanical, information concerning the Venezuelan Guayana region has been accumulated. Both the lowlands, as well as the distinctive highland mountains (‘tepuis’), evidence an outstandingly rich and diversified flora and vegetation. It has been postulated that this biological richness and the high degree of endemism are the result of long‐term and highly effective isolation suffered by the flat summit areas during extremely long geologic epochs. This static view is being challenged presently by the results of recent intensive fieldwork made in the Venezuelan Guayana. A detailed analysis of two highly evolved Guayana taxa,Stegolepis(Rapateaceae) andBonnetia(Theaceae s.l.) shows a rather uniform distribution not only in summit habitats, but also in intermediate and lowland habitats. As a whole, both genera and several related taxa prove to have occupied successfully not only the ancient summit regions of the tepuis, but also the surrounding lowlands of much more recent geomorphological origin. Palaeoecological research also supports the hypothesis that the entire Guayana Shield area has been affected by climatic oscillations during the recent past as have the nearby Andes. This implies significant past fluctuations of the altitudinal vegetation belts in the tepui area and could well explain the wide altitudinal gradient of most of the Guayana Highland taxa. Also, the presence of convergent ‘paramoid’ vegetation types on the summits of the Chimantá Massif, indicates active speciation not only at the systematic level, but especially at the ecologic level. Thus, it is proposed that the Guayana highland and lowland biota have been and still are dynamically and genetically interdependent, not only within the Guayana region itself, but also with the adjacent complex of lowland and mountain biota.

ISSN:0040-0262    

DOI:10.2307/1221102

出版商:Wiley    

年代:2019

数据来源: WILEY

摘要:

SummaryA distribution pattern analysis of 377 Cuban liverworts and 386 mosses shows a relatively high rate of endemism (11.4% and 12.2%, respectively), which is comparable to the rate of endemism in Cuban ferns but much lower than phanerogamic endemism (51.4%). In the Cuban bryoflora neotropical and Caribbean elements as well as Antillean subendemics prevail. The species/genus ratio (4:1 for the liverworts and 2:7 for the mosses), and the relatively high insularity index (3:1 for liverworts and 5:0 for mosses) are indicative of long‐term isolation of the Cuban bryophyte flora and the large size of the island.

ISSN:0040-0262    

DOI:10.2307/1221103

出版商:Wiley    

年代:2019

数据来源: WILEY

摘要:

SummaryThe case is made that ecological characteristics can provide valuable evidence for species delimitation in complex floras such as those of tropical rain forests. Differences between sympatric populations of morphologically similar entities in such aspects as edaphic range, reproductive phenology, pollination biology, combined with evidence for outbreeding, and for interspecific hybridization in nature assist in evaluating whether such entities behave as biological species. Current evidence on the biological nature of rain forest tree species is discussed.

ISSN:0040-0262    

DOI:10.2307/1221104

出版商:Wiley    

年代:2019

数据来源: WILEY