Léon Camille Marius Croizat

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Leon Croizat (1894-1982) Italian biogeographer.

Contents

[edit] Life

Leon Croizat Chaley was the son of French parents, and was born in 1894 in Torino, Italy, where he studied Law, in spite of his great aptitude for the natural sciences. After obtaining his degree, he concentrated on the sciences, specializing in botany and zoology, studying important aspects of the distribution and evolution of the species. In fact, he generated a new current of thought, opposed in some respects to Darwinism, and the evolution and dispersion of biota. At the end of World War I. Between 1941 and 1946, he immigrated to the United States, where he was in charge of the Arnold Arboretum of Harvard University. In 1947 he arrived at Venezuela, invited by the botanist Henri Pittier, to work in this field. He obtained a position in the Faculty of Agronomy of the Central University of Venezuela. In 1951 he was promoted to ordinary professor of botany and ecology in the University of The Andes. Between 1951 and 1952 he participated as botanist in the French-Venezuelan expedition to discover the sources of the Orinoco, with Prof. Jose Maria Cruxent. Croizat also was honoured by Venezuela with the Henri Pittier Order of Merit in Conservation, and by the government of Italy with the Order of Merit. He died at Coro.

The standard author abbreviation Croizat is used to indicate this individual as the author when citing a botanical name.[1]

[edit] Concepts

Panbiogeography is a discipline based on the analysis of patterns of distribution of organisms. The method analyzes biogeographic characters through the drawing of tracks, and derives information from the form and orientation of those tracks. The track is a line connecting disjunct areas of a particular taxon. Several individual tracks form a generalized track, where the individual components are relict fragments.

In graph theory a track consists of a minimal spanning tree connecting all sites by the shortest paths (Page 1987). Generalized tracks bring up as a result of many coincident depicted by particular tracks, giving a space criterion of biogeographical homology. A node arises from the intersection of two or more tracks.

To explain disjunct distributions, he proposed the existence of broadly distributed ancestor that established its range during a period of mobility, following a form-making process around particular centers. Disjunctions are explained as extinctions in the previously continuous range. Orthogenesis is a term used by Croizat, in his words “... in a pure mechanistic sense (Croizat 1984, p. 676), its refers to the fact that a variation in form is limited and constrained (Colacino 1997). Croizat considers evolution as consisting of two processes in interplay i. e. orthogenesis and adaptation

[edit] Croizat wrote

  • Organism evolution is function of time, space and form.
  • Of these three essential factor, space might be said to be one with which biogeography is primarily concerned. However space necessarily interplays with time and form, therefore the three factors are as one of biogeographic concern (Croizat 1964).

[edit] Selected works

(Many other see Bibliography external link)

  • "Panbiogeography". Self published, 1952.
  • "Space, Time Form: The biological synthesis". Self published, Caracas, 1962.
  • Croizat L. 1982. Vicariance/Vicariism, Panbiogeography, "Vicariance Biogeography," Etc.: A Clarification. Systematic Zoology 31, 291-304.

[edit] Links

[edit] References