Paul Jaccard (18 November 1868 in Sainte-Croix – 9 May 1944 in Zurich) was a professor of botany and

plant physiology Plant physiology is a subdiscipline of botany concerned with the functioning, or physiology, of plants. Closely related fields include plant morphology (structure of plants), plant ecology (interactions with the environment), phytochemistry (bi ...

at the

ETH Zurich (colloquially) , former_name = eidgenössische polytechnische Schule , image = ETHZ.JPG , image_size = , established = , type = Public , budget = CHF 1.896 billion (2021) , rector = Günther Dissertori , president = Joël Mesot , ac ...

. He studied at the University of Lausanne and

(PhD 1894). He continued studies in Paris with Gaston Bonnier. He developed the Jaccard index of similarity (he called it ''coefficient de communauté'') and published it in 1901.Jaccard, P. (1901) Distribution de la flore alpine dans le bassin des Dranses et dans quelques régions voisines. Bulletin de la Société Vaudoise des Sciences Naturelles 37, 241-272. He also introduced the use of the species-to-genus ratio (he called it ''generic coefficient'') in

biogeography Biogeography is the study of the distribution of species and ecosystems in geographic space and through geological time. Organisms and biological communities often vary in a regular fashion along geographic gradients of latitude, elevation, ...

.Jaccard, P. (1901) Étude comparative de la distribution florale dans une portion des Alpes et des Jura. Bulletin de la Société Vaudoise des Sciences Naturelles 37, 547-579. In the 1920s, Paul Jaccard engaged in a dispute with the Finnish

botanist Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the Ancient Greek wo ...

and

phytogeographer Phytogeography (from Greek φυτόν, ''phytón'' = "plant" and γεωγραφία, ''geographía'' = "geography" meaning also distribution) or botanical geography is the branch of biogeography that is concerned with the geographic distribution o ...

Alvar Palmgren Alvar Palmgren (28 April 1880 – 30 November 1960) was a Finnish botanist and plant ecologist. Palmgren studied botany at the University of Helsinki under professor J.P. Norrlin. He graduated (Fil.kand.) in 1906 and obtained his Ph.D. in 1914. H ...

over the interpretation of species-to-genus ratio, as evidence of competitive exclusion (as held by Jaccard) or attributable to random sampling (as held by Palmgren).Järvinen, Olli (1982) Species-To-Genus Ratios in Biogeography: A Historical Note. Journal of Biogeography 9 (4): 363-370.
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* {{DEFAULTSORT:Jaccard, Paul 1868 births 1944 deaths 19th-century Swiss botanists ETH Zurich faculty 20th-century Swiss botanists