Léon Camille Marius Croizat
Encyclopedia
Leon Camille Marius Croizat (July 16, 1894 - November 30, 1982) was a French
-Italian
scholar and botanist who developed a synthesis of evolution of biological form over space, in time, which he named Panbiogeography
.
, 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 biological species. In fact, he generated a novel current of thought, opposed in some respects to Darwinism
, on the evolution and dispersal of biota over space, through time. Between 1936 and 1946, he lived in the United States, where he worked as a technical assistant invited by Dr E. D. Merrill, director of the Arnold Arboretum of Harvard University
.
In 1947, Croizat arrived at Venezuela
, invited by the botanist Henri Pittier
. 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, Venezuela. Between 1951 and 1952 he participated as botanist in the Franco-Venezuelan expedition to discover the sources of the Orinoco
, with Prof. Jose Maria Cruxent. At this time he divorced from his first wife and married his second wife, Catalina, an Hungarian
immigrant. In 1953 Croizat gave up all official academic positions to work full time on biological problems. Croizat and his wife lived in Caracas
until 1976, when they took over as first directors of the “Jardin Botanico Xerofito” in Coro
, a city about 400 kilometers west of Caracas; a botanical garden which they founded and had worked to establish since 1970.
Croizat died at Coro on November 30, 1982 of a heart attack. During his life, Croizat has published around 300 scientific papers and seven books, amounting to more than 15,000 printed pages. He was honoured by Venezuela with the Henri Pittier Order of Merit in Conservation, and by the government of Italy with the Order of Merit. Several plant and animal species have been named after Croizat .
is a discipline based on the analysis of patterns of distribution of organisms. The method analyzes biogeographic distributions through the drawing of tracks, and derives information from the form and orientation of those tracks. A track is a line connecting collection localities or disjunct areas of a particular taxon
. Several individual tracks for unrelated groups of organisms form a generalized ('standard') track, where the individual components are relict fragments of an ancestral, more widespread biota fragmented by geological and/or climatic changes. A node arises from the intersection of two or more generalized tracks
In graph theory
a track is equated to a minimum spanning tree
connecting all localities by the shortest path.
To explain disjunct distributions, Croizat proposed the existence of broadly distributed ancestors that established its range during a period of mobilism, followed by a form-making process over a broad front. 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" , which refers to the fact that a variation in form is limited and constrained . Croizat considered organism evolution as a function of time, space and form. Of these three essential factors, space is the 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.
Although authors belonging to the dispersalist establishment have dismissed Croizat’s contributions, others have considered Croizat as one of the most original thinkers of modern comparative biology, whose contributions provided the foundation of a new synthesis between earth and life sciences. Panbiogeography became established as a productive research programme in historical biogeography
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
-Italian
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
scholar and botanist who developed a synthesis of evolution of biological form over space, in time, which he named Panbiogeography
Panbiogeography
Panbiogeography originally proposed by the French-Italian scholar Léon Croizat , is a cartographic approach to biogeography that basically plots distributions of a particular taxon or group of taxa on maps and connects the disjunct distribution areas or collection localities together with lines...
.
Life
Croizat was the son of French parents, and was born in TorinoTurin
Turin is a city and major business and cultural centre in northern Italy, capital of the Piedmont region, located mainly on the left bank of the Po River and surrounded by the Alpine arch. The population of the city proper is 909,193 while the population of the urban area is estimated by Eurostat...
, Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
, 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 biological species. In fact, he generated a novel current of thought, opposed in some respects to Darwinism
Darwinism
Darwinism is a set of movements and concepts related to ideas of transmutation of species or of evolution, including some ideas with no connection to the work of Charles Darwin....
, on the evolution and dispersal of biota over space, through time. Between 1936 and 1946, he lived in the United States, where he worked as a technical assistant invited by Dr E. D. Merrill, director of the Arnold Arboretum of Harvard University
Harvard University
Harvard University is a private Ivy League university located in Cambridge, Massachusetts, United States, established in 1636 by the Massachusetts legislature. Harvard is the oldest institution of higher learning in the United States and the first corporation chartered in the country...
.
In 1947, Croizat arrived at Venezuela
Venezuela
Venezuela , officially called the Bolivarian Republic of Venezuela , is a tropical country on the northern coast of South America. It borders Colombia to the west, Guyana to the east, and Brazil to the south...
, invited by the botanist Henri Pittier
Henri François Pittier
Henri François Pittier was a Swiss-born geographer and botanist, who moved to Costa Rica in 1887, where he founded the Physical Geographic Institute and an herbarium. Henri Pittier National Park in Venezuela is named after him.-References:...
. He obtained a position in the Faculty of Agronomy of the Central University of Venezuela
Central University of Venezuela
The Central University of Venezuela is a premier public University of Venezuela located in Caracas...
. In 1951 he was promoted to ordinary professor of botany and ecology in the University of the Andes, Venezuela. Between 1951 and 1952 he participated as botanist in the Franco-Venezuelan expedition to discover the sources of the Orinoco
Orinoco
The Orinoco is one of the longest rivers in South America at . Its drainage basin, sometimes called the Orinoquia, covers , with 76.3% of it in Venezuela and the remainder in Colombia...
, with Prof. Jose Maria Cruxent. At this time he divorced from his first wife and married his second wife, Catalina, an Hungarian
Hungary
Hungary , officially the Republic of Hungary , is a landlocked country in Central Europe. It is situated in the Carpathian Basin and is bordered by Slovakia to the north, Ukraine and Romania to the east, Serbia and Croatia to the south, Slovenia to the southwest and Austria to the west. The...
immigrant. In 1953 Croizat gave up all official academic positions to work full time on biological problems. Croizat and his wife lived in Caracas
Caracas
Caracas , officially Santiago de León de Caracas, is the capital and largest city of Venezuela; natives or residents are known as Caraquenians in English . It is located in the northern part of the country, following the contours of the narrow Caracas Valley on the Venezuelan coastal mountain range...
until 1976, when they took over as first directors of the “Jardin Botanico Xerofito” in Coro
Santa Ana de Coro
Coro is the capital of Falcón State and the oldest city in the west of Venezuela.-History:The city was founded on July 26, 1527 by Spanish colonists. The name "Coro" is believed to be an indigenous word meaning "wind".The city had a turbulent history in colonial times and suffered a number of...
, a city about 400 kilometers west of Caracas; a botanical garden which they founded and had worked to establish since 1970.
Croizat died at Coro on November 30, 1982 of a heart attack. During his life, Croizat has published around 300 scientific papers and seven books, amounting to more than 15,000 printed pages. He was honoured by Venezuela with the Henri Pittier Order of Merit in Conservation, and by the government of Italy with the Order of Merit. Several plant and animal species have been named after Croizat .
Concepts
PanbiogeographyPanbiogeography
Panbiogeography originally proposed by the French-Italian scholar Léon Croizat , is a cartographic approach to biogeography that basically plots distributions of a particular taxon or group of taxa on maps and connects the disjunct distribution areas or collection localities together with lines...
is a discipline based on the analysis of patterns of distribution of organisms. The method analyzes biogeographic distributions through the drawing of tracks, and derives information from the form and orientation of those tracks. A track is a line connecting collection localities or disjunct areas of a particular taxon
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
. Several individual tracks for unrelated groups of organisms form a generalized ('standard') track, where the individual components are relict fragments of an ancestral, more widespread biota fragmented by geological and/or climatic changes. A node arises from the intersection of two or more generalized tracks
In graph theory
Graph theory
In mathematics and computer science, graph theory is the study of graphs, mathematical structures used to model pairwise relations between objects from a certain collection. A "graph" in this context refers to a collection of vertices or 'nodes' and a collection of edges that connect pairs of...
a track is equated to a minimum spanning tree
Minimum spanning tree
Given a connected, undirected graph, a spanning tree of that graph is a subgraph that is a tree and connects all the vertices together. A single graph can have many different spanning trees...
connecting all localities by the shortest path.
To explain disjunct distributions, Croizat proposed the existence of broadly distributed ancestors that established its range during a period of mobilism, followed by a form-making process over a broad front. Disjunctions are explained as extinctions in the previously continuous range. Orthogenesis
Orthogenesis
Orthogenesis, orthogenetic evolution, progressive evolution or autogenesis, is the hypothesis that life has an innate tendency to evolve in a unilinear fashion due to some internal or external "driving force". The hypothesis is based on essentialism and cosmic teleology and proposes an intrinsic...
is a term used by Croizat, in his words "... in a pure mechanistic sense" , which refers to the fact that a variation in form is limited and constrained . Croizat considered organism evolution as a function of time, space and form. Of these three essential factors, space is the 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.
Although authors belonging to the dispersalist establishment have dismissed Croizat’s contributions, others have considered Croizat as one of the most original thinkers of modern comparative biology, whose contributions provided the foundation of a new synthesis between earth and life sciences. Panbiogeography became established as a productive research programme in historical biogeography
Selected works
- Manual of Phytogeography or An Account of Plant Dispersal Throughout the World. Junk, The Hague, 1952. 696 pp.
- Panbiogeography or An Introductory Synthesis of Zoogeography, Phytogeography, Geology; with notes on evolution, systematics, ecology, anthropology, etc.. Published by the author, Caracas, 1958. 2755 pp.
- Principia Botanica or Beginnings of Botany. Published by the author, Caracas, 1961. 1821 pp.
- Space, Time, Form: The Biological Synthesis. Published by the author, Caracas, 1964. 881 pp
- Croizat L. 1982. Vicariance/vicariism, panbiogeography, "vicariance Biogeography," etc.: a clarification. Systematic Zoology 31: 291-304.