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Geological History of Panama Great American Biotic Exchange
and the Geological History of Panama Great American Biotic Exchange
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Isthmus of Panama The Isthmus of Panama, in the past has been known as the Isthmus of Darien, it is the narrow strip of land that lies between the Caribbean Sea and the Pacific Ocean, linking Central and South America.
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MYA Geological Ages
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Pangea ~200 mya
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Pangea splits 135 mya Laurasia Gondwana
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Gondwana splits 100 mya
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Quaternary ~2-3 mya
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Formation of Isthmus 5 mya Early Pliocene 7 mya Late Miocene
3mya Late Pliocene 5 mya Early Pliocene 7 mya Late Miocene 15 mya Middle Miocene
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Geological History of Panama
Before ~4 mya Panama represented by island archipelago Islands arose by tectonic uplift Sea level changes modified the character of the “stepping stone” link Glaciations late Cretaceous: 300 m higher Pleistocene minimum: 92 m lower Today, melt all polar ice: 60 m higher Darien lowlands: 84 m Costa Rica/Nicaragua lowlands: 34 m
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Geological History of Panama
Before ~4 mya Oceanic barrier to migration between NA & SA Flora & fauna of SA were more like Africa/Australia than NA E.g. marsupials were restricted mostly to SA/Australia Flora & fauna of NA were more like Europe Marsupial fossils in NA (extinct since the Miocene) probably originated in Europe
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Geological History of Panama
Before ~4 mya Some N <=> S migration occurred Early tertiary 5 amphibians to NA Late Tertiary 1 salamander to SA Late Tertiary 8 reptile families to NA, 4 to SA By Early Tertiary few mammals migrated Few marsupials & placentals to NA Notoungulates to NA Late Miocene raccoon & kin to SA, 2 ground sloths to NA
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Geological History of Panama
Before ~4 mya How these pre-Panamanian migrations occurred is debated a proto-Antillean land bridge? Island hopping?
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Geological History of Panama
Before ~4 mya Panama’s biodiversity was low Limited land area Limited altitudinal zonation Limited highland areas Paleocommunities Fringing mangrove forests Floating or submerged freshwater communities Moderate altitude cloud forest
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Geological History of Panama
Before ~4 mya SA hosted 29 land mammal families NA hosted 27 land mammal families 58 total families
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Geological History of Panama
~ 3 mya 4 tectonic plates collided Sea level dropped significantly Panama arose to provide a dry land bridge between SA and NA
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Panama originated from tectonic rather than volcanic events
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Geological History of Panama
~ 3 mya Late Pliocene, Early Pleistocene migrations 10 bird families to SA, 2 to NA 15 mammalian families to SA, 7 to NA 3 survived N of Mexico opossum, armadillo, porcupine 23 families of other vertebrates to NA, 18 to SA
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Biogeoraphic History of Panama
The Great American Interchange Gradual migrations N => S during periods of cooling Stadial periods and Glaciations S => N during periods of warming Interglacial and interstadial
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Biogeoraphic History of Panama
Between 3 & 2 mya Pleistocene - soon after the migrations began Extinction of several SA groups Notoungulates
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Biogeoraphic History of Panama
Between 3 & 2 mya Pleistocene - soon after the migrations began Extinction of several SA groups Notoungulates Litopterns
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Biogeoraphic History of Panama
Between 3 & 2 mya Pleistocene - soon after the migrations began Extinction of several SA groups Notoungulates Litopterns Marsupial carnivores
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Biogeoraphic History of Panama
Between 3 & 2 mya Pleistocene - soon after the migrations began Extinction of several SA groups Notoungulates Litopterns Marsupial carnivores Flightless birds
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Phorusrhacids : Terror Bird
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Biogeoraphic History of Panama
Between 3 & 2 mya Pleistocene - soon after the migrations began Extinction of several SA groups Notoungulates Litopterns Marsupial carnivores Sloths extended far into NA before extinction
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Biogeoraphic History of Panama
Before ~4 mya SA hosted 29 land mammal families NA hosted 27 land mammal families 58 total families Soon after the opening of the land bridge 22 shared families 7 from NA, 14 from SA, 1 doubtful SA: 17 native families confined, NA: 9
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Biogeography of Panama
Before ~4 mya SA hosted 29 land mammal families NA hosted 27 land mammal families 58 total families Soon after the opening of the land bridge 22 shared families 7 from NA, 14 from SA, 1 unsure SA: 17 native families confined, NA: 9 Recently 15-20ish shared, confined to SA, 9 confined to NA
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CA and SA Mammal Families
Bull-dog Bats, Fish-eating Bats Noctilionidae Anteaters Myrmecophagidae Hutias, Nutria Capromyidae*4 Pacas Agoutidae Agoutis, Dasyproctidae Disc-winged Bats Thyropteridae New World Monkeys Cebidae Marmosets, Tamarins Callitrichidae West Indian Sloth &Two-toed Tree Sloth Megalonychidae Funnel-eared Bats Natalidae SA Only Shrew or Rat Opossums Caenolestidae Smokey Bats Furipteridae Three-toed Tree Sloths Bradypodidae Guinea Pigs, etc Caviidae Capybara Hydrochaeridae Pacarana Dinomyidae Chinchilla Rats Abrocomidae Spiny Rats Echimyidae Octodonts, Degu Octodontidae Tuco Tucos Ctenomyidae Coypu Myocastoridae*3 CA & SA
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Pan-American Mammal Families
Pocket Mice, Kangaroo Rats Heteromyidae Pocket Gophers Geomyidae New World Porcupines Erethizontidae Peccaries, Javelinas Tayassuidae Racoons, etc Procyonidae Opossums Didelphidae Armadillos Dasypodidae Shrews Soricidae Common Bats Vespertilionidae Dogs, Wolves, Foxes Canidae Free-tailed Bats Molossidae Weasels, Otters, Skunks, Badgers Mustelidae Bears Ursidae Cats Felidae Squirrels, Chipmonks, Marmots, Prarie Dogs etc Sciuridae Eared Seals, Sea Lions Otariidae Rats, Mice, Voles, Gerbils, Hamsters, etc Muridae Cattle, Sheep, Goats, Antelopes, etc*** Bovidae Deer, etc Cervidae Hares and Rabbits Leporidae
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Biogeography of Panama
Biodiversity today SA is about as species rich as before, but different NA is less rich, but more similar in composition Both achieved maximum density soon after opening of the bridge and then declined
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Biogeography of Panama
Marsupial Migrations
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Biogeography of Panama
Before ~4 mya Panama’s biodiversity was low Limited land area Limited altitudinal zonation Limited highland areas Paleocommunities Fringing mangrove forests Floating or submerged freshwater communities Moderate altitude cloud forest
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Biogeography of Panama
~3-2 mya Isthmus land bridge used by species displaced by climatic changes
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Biogeography of Panama
Names Inter/Glacial Period (kya) Epoch N. American S. American interglacial present – 12 Holocene Wisconsin Llanquihue glacial period 12 – 110 Pleistocene Sangamonian 110 – 130 Illinoian Santa María 130 – 200 Yarmouth interglacial(s) 200 – 300/380 Kansan Río Llico glacial period(s) 300/380 – 455 Aftonian 455 – 620 Nebraskan Caracol 620 – 680 Pastonian Stage 600 – 800 Pre-Pastonian Stage 800 – 1300 Bramertonian Stage 1300 – 1550
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Biogeography of Panama
Today As Panama’s geographic character became more complex - biodiversity increased Each migrant species passed through Panama Some stayed Some passed through Some stayed and sent representatives on Immigrant species occupied newly developing niches
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Biogeography of Panama
Panama’s biodiversity today 960 bird species 220 mammal species 240 reptile species 160 amphibian species >10,000 vascular plants All species arrived since Panama arose All “native” or “endemic” species arrived from NA or SA
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