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Origins of Heterospory and the Seed Habit: The Role of Heterochrony

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dc.contributor.author DiMichele, William A. en
dc.contributor.author Davis, Jerrold I. en
dc.contributor.author Olmstead, Richard G. en
dc.date.accessioned 2009-03-24T19:13:27Z
dc.date.available 2009-03-24T19:13:27Z
dc.date.issued 1989
dc.identifier.citation DiMichele, William A., Davis, Jerrold I., and Olmstead, Richard G. 1989. "<a href="https%3A%2F%2Frepository.si.edu%2Fhandle%2F10088%2F7136">Origins of Heterospory and the Seed Habit: The Role of Heterochrony</a>." <em>Taxon</em>. 38 (1):1&ndash;11. en
dc.identifier.issn 0040-0262
dc.identifier.uri http://hdl.handle.net/10088/7136
dc.description.abstract The origin of the seed-plant life history, and subsequent diversification of seed morphology, should be considered two independent, fundamentally distinct evolutionary problems. Gametophytic endospory may have arisen paedomorphically from homosporous ancestors, specifically by progenesis in the gametophyte generation. Heterospory and gametophytic unisexuality are not necessarily evolutionary antecedents of endospory; rather, they may have arisen as developmental consequences of endospory. Once seeds existed, their early pattern of diversification was not one of gradual change in form, but of a proliferation of integumentary types differing widely from one another. Subsequently, the morphological spectrum narrowed, with closed integuments eventually prevailing. This two-stage pattern of diversity suggests an initial phenotypic breakthrough into a largely &quot;empty&quot; adaptive zone, followed by intensified biotic competition as the adaptive zone filled en
dc.format.extent 331744 bytes
dc.format.mimetype application/pdf
dc.language.iso en_US
dc.relation.ispartof Taxon en
dc.title Origins of Heterospory and the Seed Habit: The Role of Heterochrony en
dc.type Journal Article en
dc.identifier.srbnumber 20364
rft.jtitle Taxon
rft.volume 38
rft.issue 1
rft.spage 1
rft.epage 11
dc.description.SIUnit NH-Paleobiology en
dc.description.SIUnit NMNH en
dc.citation.spage 1
dc.citation.epage 11

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