Evolution of North AmericanEvolution of North AmericanVegetation and FloraVegetation and FloraNorth American Flora - the Fossil RecordThe study of the NorthThe study of the NorthAmerican flora andAmerican flora andvegetation - its history andvegetation - its history andassembly - begins in theassembly - begins in thelate Cretaceous with thelate Cretaceous with themajor events staged later inmajor events staged later inthe Tertiary of the Cenozoicthe Tertiary of the CenozoicThe final shaping of North American (andThe final shaping of North American (andGreat Lakes) flora and vegetation occursGreat Lakes) flora and vegetation occursduring the Recent Epoch (Holocene)during the Recent Epoch (Holocene)following the glaciation of the Pleistocenefollowing the glaciation of the PleistocenePleistocene HoloceneNorth American Flora - the Fossil RecordPermianPermian North America North America260 mya260 mya••N. America near equatorN. America near equator••Appalachian MountainsAppalachian Mountainswell developedwell developedNorth American Flora - the Fossil RecordTo understand North American biogeography, follow itTo understand North American biogeography, follow itthrough the end of Paleozoic and Mesozoicthrough the end of Paleozoic and MesozoicTriassicTriassic North America North America230 mya230 mya••N. America moves northN. America moves north••Extensive volcanicExtensive volcanicactivity in oceanicactivity in oceanicwestern N. Americawestern N. AmericaNorth American Flora - the Fossil RecordTo understand North American biogeography, follow itTo understand North American biogeography, follow itthrough the end of Paleozoic and Mesozoicthrough the end of Paleozoic and MesozoicJurassicJurassic North America North America170 mya170 mya••N. America moves northN. America moves north••Appalachians erodingAppalachians eroding••Western mountainWestern mountainbuilding beginsbuilding begins••Interior sea formsInterior sea formsNorth American Flora - the Fossil RecordTo understand North American biogeography, follow itTo understand North American biogeography, follow itthrough the end of Paleozoic and Mesozoicthrough the end of Paleozoic and MesozoicCretaceousCretaceous North America North America100 mya100 mya••Interior Seaway fromInterior Seaway fromGulf of Mexico to ArcticGulf of Mexico to ArcticCircleCircleNorth American Flora - the Fossil RecordTo understand North American biogeography, follow itTo understand North American biogeography, follow itthrough the end of Paleozoic and Mesozoicthrough the end of Paleozoic and MesozoicThe end of the Cretaceous and beginning of the Tertiary (100-The end of the Cretaceous and beginning of the Tertiary (100-50 mya) saw the warmest temperatures since the PreCambrian50 mya) saw the warmest temperatures since the PreCambrianEffect wasEffect waswidespread overwidespread overlatitudeslatitudesCosmopolitan florasCosmopolitan florasexisted despiteexisted despitePangaea breakupPangaea breakupNorth American Flora - the Late CretaceousTyrannosaurusTyrannosaurus within a stand of trees composed of bald cypress, within a stand of trees composed of bald cypress,metasequoia, sequoia, sycamore and magnolia - eastern Montanametasequoia, sequoia, sycamore and magnolia - eastern Montana66 mya66 myaThe end of the Cretaceous was so warm that dinosaurs lived inThe end of the Cretaceous was so warm that dinosaurs lived intropical settings in North Americatropical settings in North AmericaNorth American Flora - the Late CretaceousEdmontosaurusEdmontosaurus within a stand of deciduous within a stand of deciduoussubtropical trees in Alaska - 66 myasubtropical trees in Alaska - 66 myaWarm conditions existed as far north asWarm conditions existed as far north asAlaska and allowed dinosaurs to exist thatAlaska and allowed dinosaurs to exist thatfar north - although they apparently had tofar north - although they apparently had tomigrate with onset of long nightsmigrate with onset of long nightsBreadfruit (figBreadfruit (figfamily) infamily) inAlaskaAlaskaNorth American Flora - the Late CretaceousFloristic exchangeFloristic exchange was widely was widelypossible between Eastern Asiapossible between Eastern Asiaand Western North America viaand Western North America viaBeringiaBeringiaFloristic exchangeFloristic exchange was also was alsowidely possible betweenwidely possible betweenEastern North America andEastern North America andWestern Eurasia via the NorthWestern Eurasia via the NorthAtlantic that had not separatedAtlantic that had not separatedyetyetNorth American Flora - the Late CretaceousNorth American Flora - the Late CretaceousWhy so warm?Why so warm? effects of Pangaea breakup effects of Pangaea breakup••Young, hot ocean crustYoung, hot ocean crust••Sea levels pushed up bySea levels pushed up bycrustcrust••Cretaceous: sea levelCretaceous: sea levelhighest since Ordovicianhighest since Ordovician••1/3 of current exposed1/3 of current exposedland was underwaterland was underwaterContributing to this moderation of climate were the largeContributing to this moderation of climate were the largeepicontinental seasepicontinental seas that existed in North America and Eurasia in the that existed in North America and Eurasia in theLate Cretaceous due to high sea levelsLate Cretaceous due to high sea levelsNorth American Flora - the Late CretaceousThe The epicontinental Seaepicontinental Sea in North America extended from the Gulf of in North America extended from the Gulf ofMexico through the western interior lowlands to the Arctic dividing NorthMexico through the western interior lowlands to the Arctic dividing NorthAmerica in halfAmerica in halfIn North America, the footprint of this vast inlandIn North America, the footprint of this vast inlandsea and its subsequent retreat is clearly seen in thesea and its subsequent retreat is clearly seen in theextensive shale deposits in places like Coloradoextensive shale deposits in places like ColoradoNorth American Flora - the Late CretaceousAn aerial view of the eastern coastAn aerial view of the eastern coastline of western North America and theline of western North America and theInterior Cretaceous Seaway, some 75Interior Cretaceous Seaway, some 75million years agomillion years ago•• water bodies absorb more heat water bodies absorb more heatthan land and releases it morethan land and releases it moreslowlyslowly•• these inland seaways lowered the these inland seaways