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Donald Irving Williamson (born 8 January 1922, in Alnham, England) is a British planktologist and carcinologist. He gained his first degree from the Durham University in 1942, his PhD from the same university in 1948, and a DSc from the Newcastle University in 1972. He worked at the Port Erin Marine Laboratory of the University of Liverpool from 1948 to 1997,〔http://www.edge.org/3rd_culture/bios/williamson.html〕 and has published on the Irish Sea plankton, crustacean behaviour and taxonomy, and crustacean larvae. ==Works== He is also author of some speculative works on hybridisation in evolution: ''Larvae and Evolution'' (a book foreworded by Lynn Margulis and Alfred I. Tauber), ''The Origins of Larvae'' (a revised and extended edition of ''Larvae and Evolution'', not to be confounded with his 2007 article of same title published in the magazine American Scientist), and some articles on the same subject. In ''Larvae and Evolution''〔 Williamson developed a controversial hypothesis proposing the acquisition of larval stages in some marine organisms by hybridisation between two distant animal species (a speciation process referred to as hybridogenesis by Williamson). The fraction of the genome of one of the contributor species would be restricted to lead the developmental program of a newly acquired larva whereas the genome of the other contributor would drive the development of most of the adult anatomical structures. During the following years he would generalise his theory to other animal groups featuring a holometabolous development.〔 According to Williamson, these successful hybridisations would most likely occur in organisms with external fertilisation or male gamete dispersal. He acknowledges in his work ''Larvae and Evolution'' to have borrowed the idea of hybridogenesis from the well-known process of interspecific hybridisation that take place in plants. Hybrid plants generated from phylogenetically distant species can often give rise to new species if the hybrids become reproductively isolated from the progenitor populations.〔 In one of his articles Williamson contends that # there were no true larvae until after the establishment of classes in the respective phyla, # early animals hybridised to produce chimeras of parts of dissimilar species, # the Cambrian explosion resulted from many such hybridisations, # modern animal phyla and classes were produced by such early hybridisations, rather than by the gradual accumulation of specific differences. Williamson's hypothesis has been reviewed in the companion website for the eighth edition of ''Developmental Biology'' (a principal textbook of reference in the field of Developmental biology). The review can be found in the chapter 23, section 10: ''Alternative Mechanisms for Evolutionary Developmental Biology'', subsection: ''alt.evodevo: Reticulate Evolution and Sequential Chimeras'', under the header ''Sequential Chimerism''.〔 http://8e.devbio.com/article.php?ch=23&id=228〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Donald I. Williamson」の詳細全文を読む スポンサード リンク
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