The origin of angiosperms

Krassilov, Valentin

doi:10.1007/bf02860852

Cited by 74 publications

(37 citation statements)

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“…The only Early Cretaceous angiosperm leaf succession that has been reinvesti gated in close conjunction with the pollen record is from the Potomac Group (43, 67,152), and practically all other major leaf floras known are from Laurasia: North America (17,19,83,149), Europe (132), and the Asian part of the USSR (78,81,114,115,141). However, within this area certain consistent trends emerge, and although leaves are more limited to local environments of deposition (i.e.…”

Section: Implications Of the Cre Ta Ceous Re Cordmentioning

confidence: 98%

Origin of Angiosperms

Doyle¹

1978

Annu. Rev. Ecol. Syst.

194

104

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INTRODUCTION +4146The past 20 years have seen unprecedented progress toward solution of Darwin's "abominable mystery" of the origin of angiosperms, the plant group that has domi nated most terrestrial ecosystems since the middle of the Late Cretaceous, some 80 million years ago. Although studies of living plants have yielded important new insights (68,109, 124,144,145,147), the most striking advances have come from paleobotany, particularly from palynology (the study of spores and pollen) and new methods of analysis of the Cretaceous leaf record.Before the I 960s, most authors considered the fossil record of angiosperms unusu ally biased and unrevealing as a source of evidence on their origin and early evolu tion. Studies of Early Cretaceous leaf fl oras done around the turn of the century (18, 50) showed that angiosperms rose to dominance more gradually than had been previously believed (cf 8), but these studies produced identifications of early angios perm leaves with diverse modern genera and families that seemed to indicate a long period of prior diversifi cation. Such identifications, plus occasional reports of pre Cretaceous angiosperms and various analogical arguments (see 41), are the primary basis of Axelrod's theory (8-12) that the angiosperms originated and began to diversify extensively in tropical upland areas as early as the Permian or Triassic.In the apparent absence of critical fo ssil evidence, ideas on the origin of angios perms have been based largely on comparative morphology of modern plants. For example, the presence of such fe atures as vesselless wood, monosulcate pollen, free fl oral parts, and incompletely sealed carpels has been considered support for the concept that the dicot subclass Magnoliidae (128) or "ranaHan complex" includes the most primitive surviving angiosperms, and for the related euanthial theory of the fl ower-that the flower is a simple strobilus, an axis bearing micro-and megas porophylls (13-15, 33, 128, 136). Comparative evidence has also been used to argue that the angiosperms are a monophyletic group: They share unique advances such as double fertilization followed by endosperm formation; character correlations and morphological series allow departures from a euanthial, magnoliid prototype [such as the simple, unisexual fl owers of the wind-pollinated Amentiferae (Juglandaceae, . Further ANNUAL REVIEWS 366 DOYLEBetulaceae, etc)] to be interpreted as specializations within the angiosperms (33,128,136). However, these interpretations are not accepted by all authors. For example, proposes that the angiosperms evolved polyphyletically from gym nosperms with compound fe rtile branch systems called anthocorms, with groups of microsporangia or ovule-containing cupules borne on the secondary axes. Under this interpretation, the Amentiferae are as primitive as the Magnoliidae, the "fl ow-. ers" in some groups are homologous with whole anthocorms, in others with the secondary axes only, and "carpels" are sometimes derived by modification of cupules, sometimes by fusion of t...

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Section: Implications Of the Cre Ta Ceous Re Cordmentioning

confidence: 98%

Origin of Angiosperms

Doyle¹

1978

Annu. Rev. Ecol. Syst.

194

104

View full text Add to dashboard Cite

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“…The story is complicated however by possible polyphyletic beginnings with at least three major groups arising at different times and places (Krassilov, 1977), although this concept was dismissed by Cronquist (1981). In any case, taxa with tricolpate pollen (note: Avicennia pollen is tricolpate) first appeared in western Gondwana (Brenner, 1976) in the Early Cretaceous, and by the mid-Cretaceous they were dispersed widely (Barlow, 1981) .…”

Section: The Earliest Fossil Evidence Of Avicenniamentioning

confidence: 99%

Genetic diversity, distributional barriers and rafting continents ? more thoughts on the evolution of mangroves

Duke

1995

Hydrobiologia

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Without continental drift, the diversity and distribution of many species, including mangrove plants, would be very different today. First, there would be fewer pantropic genera and many more endemics . Second, their characteristics would not be as common and widespread as some are today. Continental drift has brought about the massive mixing and dispersal of genes in geologically recent times, greatly enhancing the evolutionary process ; particularly for flowering plants -the angiosperms, which evolved during this period .Mangrove plants are comprised of approximately 70 species from 20 quite different angiosperm families . Most taxa are characterized by special physiological abilities and structural forms, enabling them to live in both seasonally fluctuating saline conditions, and water-saturated soils . Their occurrence is mostly tropical, perhaps because of harsh physiological conditions of intertidal habitats ; but distributions of specific taxa do not fully concur with the idea of a completely tropical evolution, at least for some important species .At least one genus of mangrove tree, Avicennia, occurs around the world, chiefly in tropical estuarine habitats, although they also range into temperate latitudes, especially in the south . Around the world, there are no more than ten species of Avicennia recognised today, but their diagnostic determinants were inadequate prior to recent studies using both numerical analyses of morphological parameters and isozymes . Such analyses significantly reduced the number of apparent species, notably around Australia, and provided a basis for the revision of distributional records throughout the Indo West Pacific region . One species, A . marina, was found to be widespread and morphologically variable with genes divided into characteristic groupings of at least three geographic areas in the region . Based on these findings, there are several novel inferences to be made regarding the evolution of this genus . A western Gondwanan origin is proposed, with subsequent radiation of several taxa facilitated via the tectonic dispersal of southern continental fragments .

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“…However, one need not necessarily postulate that Gnetum-like plants were ancestral to all angiosperms. A polyphyletic origin of angiosperms is entertained by more and more authors in a wide range of meanings (see, e.g., Meeuse, 1975c;Hughes, 1977;Krassilov, 1977;Merxmiiller, 1977;Dilcher, 1979). According to a hypothesis by Croizat (1964), angiosperms evolved in a broad front from proangiosperms.…”

Section: Evolutionary Considerations-althoughmentioning

confidence: 99%

Vessel Structure of Gnetum and the Origin of Angiosperms

Muhammad

Sattler

1982

American Journal of Botany

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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. This content downloaded from 132.239. ABSTRACTVessel structure of Gnetum gnemon L. and G. montanum Mg. was investigated by means of light microscopy (brightfield, phase contrast and Nomarski interference optics), and scanning and transmission electron microscopy. The gyres of the first order framework are compound, consisting of three elementary strands (subunits). Pits ranging from slit-shaped to circular are formed either between the elementary strands of one gyre or between adjacent gyres. (Compound gyres are also figured forAlnus and lens-shaped pits in annular-helical elements are demonstrated for Juglans and Salix). In the two species of Gnetum studied, scalariform pits occur in addition to the well known circular pits. Scalariform perforation plates are present besides scalaroid, foraminate, and simple perforation plates as well as intermediates between the above types. These findings invalidate a common argument against the gnetalean origin of angiosperms, namely that pits and perforations of Gnetum are totally unlike those of primitive angiosperms and that therefore Gnetum must be ruled out as a potential ancestor of angiosperms. Variation in vessel structure of Gnetum is so great that it encompasses the typically circular pits of the coniferopsids as well as patterns of pits and perforation plates found in angiosperms. Some photographs of angiospermous taxa are interspersed with those of Gnetum to indicate the striking similarities. The determination of the patterns and shapes of pits and perforations is discussed in terms of four parameters: 1) the ratio of the width of the cell face to the distance between the gyres; 2) the types and distribution of the second order framework; 3) the stretching and distortion of gyres and/or second order framework; and in the case of perforations, 4) the pattern of wall and bar breakdown. Since the first parameter may change continuously, a continuum between circular pits or perforations and scalariform ones may occur. Such a continuum actually exists in Gnetum as well as in angiosperms. Patterns due to the other three of the above parameters are also formed in similar ways in both Gnetum and angiosperms. These similarities may, of course, be interpreted as the result of parallel evolution. However, when one considers the large number of angiospermous features of Gnetum, one is led to ask whether Gnetum may not have been close to the ancestral stock of all or at least some taxa of angiosperms.IT IS COMMONLY ACCEPTED that vessels of Gnetum lack scalariform pitting and are instead characterized by circular pitting and perforation plates derived from this type of pitting (e.g., Thompson). Furthermore, it is frequently emphasized that the ...

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The origin of angiosperms

Cited by 74 publications

References 30 publications

Origin of Angiosperms

Origin of Angiosperms

Genetic diversity, distributional barriers and rafting continents ? more thoughts on the evolution of mangroves

Vessel Structure of Gnetum and the Origin of Angiosperms

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