Speciation in amazonian forest birds.
11 Jul 1969-Science (American Association for the Advancement of Science)-Vol. 165, Iss: 3889, pp 131-137
About: This article is published in Science.The article was published on 1969-07-11. It has received 1863 citations till now. The article focuses on the topics: Genetic algorithm.
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TL;DR: The commonly observed high diversity of trees in tropical rain forests and corals on tropical reefs is a nonequilibrium state which, if not disturbed further, will progress toward a low-diversity equilibrium community as mentioned in this paper.
Abstract: The commonly observed high diversity of trees in tropical rain forests and corals on tropical reefs is a nonequilibrium state which, if not disturbed further, will progress toward a low-diversity equilibrium community. This may not happen if gradual changes in climate favor different species. If equilibrium is reached, a lesser degree of diversity may be sustained by niche diversification or by a compensatory mortality that favors inferior competitors. However, tropical forests and reefs are subject to severe disturbances often enough that equilibrium may never be attained.
7,795 citations
TL;DR: Any event that increases the efficiency of the predators at eating seeds and seedlings of a given tree species may lead to a reduction in population density of the adults of that species and/or to increased distance between new adults and their parents.
Abstract: A high number of tree species, low density of adults of each species, and long distances between conspecific adults are characteristic of many low-land tropical forest habitats. I propose that these three traits, in large part, are the result of the action of predators on seeds and seedlings. A model is presented that allows detailed examination of the effect of different predators, dispersal agents, seed-crop sizes, etc. on these three traits. In short, any event that increases the efficiency of the predators at eating seeds and seedlings of a given tree species may lead to a reduction in population density of the adults of that species and/or to increased distance between new adults and their parents. Either event will lead to more space in the habitat for other species of trees, and therefore higher total number of tree species, provided seed sources are available over evolutionary time. As one moves from the wet lowland tropics to the dry tropics or temperate zones, the seed and seedling predators in ...
4,267 citations
TL;DR: Hybrid zones are narrow regions in which genetically distinct populations meet, mate, and produce hybrids, and models of parapatric speciation, and of Wright's "shifting balance," involve the formation, move ment, and modification of hybrid zones.
Abstract: Hybrid zones are, roughly speaking, narrow regions in which genetically distinct populations meet, mate, and produce hybrids. They are often only a few hundred meters wide and yet may be several hundred kilometers long. They are found in a wide variety of organisms: Tables 1 and 2 list about 150 reasonably clear examples, in which there is a spatial transition between two hybridizing forms. Such a widespread and striking phenomenon requires explanation; more importantly, it offers us several ways of understanding the nature and origin of species. First, hybrid zones pose interesting questions for the taxonomist, for they contrast two views of the species: as a set of populations delimited by genetic barriers to gene exchange; and as a set of populations maintained in a particular stable equilibrium by selection. Second, the wide range of genotypes found in a hybrid zone can be used to analyze the genetic differences and selective forces that separate the taxa involved. This may allow some inferences about the way these differences evolved and, by extrapolation, about the way fully isolated species diverge from each other. Finally, models of parapatric speciation, and of Wright's "shifting balance," involve the formation, move ment, and modification of hybrid zones. Hybrid zones must be understood before the plausibility of these models can be judged. After clarifying our terminology, we will summarize the relevant theory and then see how this can be used to make inferences from field data. A notable increase in the number of detailed genetic studies of hybrid zones occurred over
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University of Amsterdam1, Naturalis2, Utrecht University3, Central University of Venezuela4, Ecopetrol5, Spanish National Research Council6, Petrobras7, Smithsonian Tropical Research Institute8, Federal University of Uberlandia9, Universidade Federal do Acre10, Academy of Natural Sciences of Drexel University11, ETH Zurich12, University of Oxford13, University of Gothenburg14, University of Zurich15
TL;DR: It is shown that Andean uplift was crucial for the evolution of Amazonian landscapes and ecosystems, and that current biodiversity patterns are rooted deep in the pre-Quaternary.
Abstract: The Amazonian rainforest is arguably the most species-rich terrestrial ecosystem in the world, yet the timing of the origin and evolutionary causes of this diversity are a matter of debate. We review the geologic and phylogenetic evidence from Amazonia and compare it with uplift records from the Andes. This uplift and its effect on regional climate fundamentally changed the Amazonian landscape by reconfiguring drainage patterns and creating a vast influx of sediments into the basin. On this “Andean” substrate, a region-wide edaphic mosaic developed that became extremely rich in species, particularly in Western Amazonia. We show that Andean uplift was crucial for the evolution of Amazonian landscapes and ecosystems, and that current biodiversity patterns are rooted deep in the pre-Quaternary.
1,790 citations
References
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TL;DR: In this article, it was shown that around the beginning of the Cenozoic, South America received a few wait immigrants-marsupials, edentates, ungulates-that reached the continent across a water barrier.
Abstract: Of the three southern continents, South America was more isolated during the Tertiary than Africa, less isolated than Australia. Its record of Cenozoic mammalian life is better than that of either. This record suggests that around the beginning of the Cenozoic, South America received a few wait immigrants-marsupials, edentates, ungulates-that reached the continent across a water barrier. The source area was probably Central America, which formed a tropical North American peninsula until near the end of Tertiary time. A few later wait immigrants reached the continent across the water barrier-rodents in the later part of the Eocene, primates then or in the early Oligocene, and procyonids perhaps late in the Miocene. From the descendants of these few immigrants a balanced fauna evolved that was strikingly different in composition from those of other continents. The evolution of the various groups composing it is briefly presented and discussed. At the end of the Tertiary the isolation of the continent ended ...
516 citations
186 citations
01 Jan 1960
TL;DR: In this paper, the uppermost 32 meters of a 2436 metre core principally of lake sediments, Pleistocene and Holocene in age from the Sabana de Bogota were analysed for its pollen content, at intervals of 10-15 cm.
Abstract: The uppermost 32 metres of a 2436 metre core principally of lake sediments, Pleistocene and Holocene in age from the Sabana de Bogota were analysed for its pollen content, at intervals of 10—15 cm. About seventy species, genera of families could be recognized, many of them for the first time. The rest of the core is being analysed and the results will be published later. The Sabana de Bogota lies at an altitude of approximately 2500 metres above sea level, 4½°—5° North of the equator, and 74°—74½° West of Greenwich. From the diagram it may be deduced that glacial and interglacial periods affected the tropics equally as Europe and North America. It also shows that the glacial periods were at the same time pluvials, and the interglacials interpluvials. Curves for the real fluctuations of the tree-line, changes of annual precipitation and changes of temperature have been calculated (fig. 5). Temperatures during the high-glacial phases of the Wurm glacial were ± 8° C lower than today, the altitude of the tree-line was some 1300 metres less than now and the snow-line showed an even greater difference (fig. 5). Radiocarbon dates prove that the parts of the section considered to be respectively Holocene and later Wurm-glacial really correspond to those ages. Moreover the temperature curve for the upper Pleistocene of the Sabana de Bogota corresponds surprisingly well with that published by Emiliani for surface ocean water and by Gross for Europe (fig. 6). With this knowledge it seemed fully justified to correlate also the older phases with the glacials and interglacials of Europe and North America, using principally the alpine nomenclature. The lowest part of the diagram seems to correspond to the end of Hiss I (= Drenthe stadial), followed by the Riss I—II interstadial, and the Riss II (= Warthe stadial). Then follows the Riss-Wurm interglacial, the Wurm-glacial (subdivided by two long interstadials, together called Interpleniglacial), and the Holocene. The more important conclusions of the present study are summarized in paragraph 12.
177 citations
01 Jan 1949
171 citations