Historical Biogeography -A History of IdeasDisjunctions: how are these distributionpatterns explained?Two main ideas:- geological eventsseparate once continuousbiota (vicariance)- dispersal events overgeological barriers(dispersalism)Disjunctions: how are these distributionpatterns explained?Vicariance paradigm:Atlantic baseline - panbiogeography- invoked by the schools of vicariancebiogeography and panbiogeographyDisjunctions: how are these distributionpatterns explained?Dispersalist paradigm:- invoked by the Wallace-Darwin tradition and islandbiogeographersVicariance vs. Dispersalsimilar pattern, different processDisjunct (vicariad) speciesDisjunct continental areasDisjunct speciesDisjunct continental areasSpecies limited to one areaDisjunct continental areasDispersal across ocean barrierDivergence inisolationWidespread speciesContinuous continental areaErection of ocean barrierDivergence inisolationVicarianceDispersalRepeated pattern? - then vicarianceDisjunct (vicariad) speciesDisjunct continental areasDisjunct speciesDisjunct continental areas1. Phylogenetic trees - clades2. Knowledge of splitting events of areas- continents, mountain erection, etc.Biogeography has relied ontwo sources of informationVicarianceDispersalVicariance vs. Dispersalhow do you decide?Species and Areas: History of IdeasCarolus Linnaeus (1707–1778) Swedish naturalist and taxonomist Developed a system to classify life thatincluded binomial nomenclature Believed in special creation and thought itwas his task to catalogue all of God's creations— called himself “God’s Registrar”.Because he thought species were immutable, aquestion that he pondered was:How did different species become adapted to somany different environments?Species and Areas: History of IdeasCarolus Linnaeus (1707–1778)“the continents in the first ages of the world lay immersed under the sea, except asingle island in the midst of this immense ocean; where all animals livedcommodiously, and vegetables were produced in the greatest luxuriance”(Linnaeus, 1781)Species and Areas: History of IdeasCarolus Linnaeus (1707–1778)His explanation (Center of Origin - Dispersal idea) was that Noah's Ark had cometo rest on Mount Ararat• This tall mountain had many different elevational zones• Each immutable species was already adapted to a particular zone• Each species spreads out to its respective environment over the globeSpecies and Areas: History of IdeasComte de Buffon (1707–1788)The zoologist de Buffon had two problems withLinnaeus' view of the origin and spread of life.(1) He observed that different parts of the world,even those with similar conditions, were inhabitedby distinct kinds of plants and animals.(1) He found it unlikely that species would be ableto disperse across inhospitable habitats (and therewere many inhospitable barriers).Species and Areas: History of Ideas• Life originated on northern landmasses (Center of Origin)• Life spread southward (Dispersal) as climates cooled• Adapting and “evolving” such that each area came to contain distinct speciesComte de Buffon (1707–1788)Species and Areas: History of IdeasBuffon's Law — environmentally similarbut isolated regions have distinctassemblages of mammals and birds (thisis often considered the first principle ofbiogeography) [like Humboldt’s idea]Comte de Buffon (1707–1788)Two important concepts expressed byBuffon are now central to modernbiogeography: climates and species aremutable (changeable)Species and Areas: History of IdeasThus before end of the 18th century, two important ideas had emergedconcerning the nature of the distribution of species around the world:1. “Center of Origin” from whichspecies originate and disperse2. Ecological conditions control theregularities in distribution patternsKarl Willdenow (1765–1812)German botanist, provided a major treatise onplant geography. He described the floristicprovinces of Europe and offered a novelinterpretation for their origin as well as others inthe southern hemisphere.one of the first “vicariance” thoughts!Species and Areas: History of IdeasAlexander von Humboldt (1769–1859)“In order to come to a decision as to the existencein ancient times of a connection betweenneighboring continents, geology bases itself on theanalogous structures of coastlines, on the similarityof animals inhabiting them and on oceansurroundings. Plant geography furnishes mostimportant material for this kind of research . . . itfinds the separation of Africa and South Americanoccurred before the development of livingorganisms” (von Humboldt and Bonpland, 1805)Despite Willdenow’s foresight, Humboldtarticulated the first vicariance argument . . .Species and Areas: History of Ideas“. . . It is this science which can decide whetherthe entire surface of the earth was coveredsimultaneously with diverse plants, or whetheraccording to the ancient myths of various peoples,the globe, having regained its repose, firstproduced plants only in a single region from whichthe sea currents carried them progressively, duringthe course of centuries, into the more distant zones”(von Humboldt and Bonpland, 1805)He than laid down the gauntlet on the issuebetween vicariance and dispersal . . .Humboldt was convinced that the history of organisms and the history ofthe earth were intimately linked — also convinced that the Linnaean ideathat organisms originated in one area and migrated to others was wrongAlexander von Humboldt (1769–1859)Species and Areas: History of Ideas“In order to solve the great problem as to themigration of plants, plant geography descends intothe bowels of the earth: there it consults the ancientmonuments which nature has left in the form ofpetrifications in the fossil wood and coal bedswhich constitute the burial places of the firstvegetation of our planet” (von Humboldt andBonpland, 1805)He also described how this debate could besolved . . .. . . and that this study of paleobotany wouldprovide clues about the distribution of plantsaround the globe and clues to what the pastclimates would have been likeAlexander von Humboldt (1769–1859)Species and Areas: History of IdeasBy the turn of the 19th century, three sets ofideas now existed on organismal distributions:1. “Center of Origin” from which speciesoriginate and disperse2. Changes in earth history (vicariance)could explain present day patterns3. Ecological conditions control theregularities in distribution