And the Geological History of Panama Great American Biotic Exchange.

and

the

Geological History of Panama

Great American Biotic Exchange

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.

Isthmus of Panama

Geological Ages

MYA

Pangea

~200 mya

Pangea splits

135 myaLaurasiaGondwana

Gondwana splits

100 mya

Quaternary

~2-3 mya

Formation of Isthmus

15 mya Middle Miocene7 mya Late Miocene5 mya Early Pliocene3mya Late Pliocene


Before ~4 myaPanama represented by island archipelago

Islands arose by tectonic upliftSea level changes modified the character of

the “stepping stone” linkGlaciations late Cretaceous: 300 m higherPleistocene minimum: 92 m lowerToday, melt all polar ice: 60 m higher

Darien lowlands: 84 mCosta Rica/Nicaragua lowlands: 34 m


Before ~4 mya Oceanic barrier to migration between NA & SAFlora & fauna of SA were more like

Africa/Australia than NAE.g. marsupials were restricted mostly to

SA/Australia

Flora & fauna of NA were more like EuropeMarsupial fossils in NA (extinct since the Miocene)

probably originated in Europe


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


Before ~4 mya How these pre-Panamanian migrations

occurred is debated a proto-Antillean land bridge? Island hopping?


Before ~4 myaPanama’s biodiversity was low

Limited land areaLimited altitudinal zonationLimited highland areas

PaleocommunitiesFringing mangrove forestsFloating or submerged freshwater communitiesModerate altitude cloud forest


Before ~4 myaSA hosted 29 land mammal familiesNA hosted 27 land mammal families58 total families


~ 3 mya4 tectonic plates collidedSea level dropped significantlyPanama arose to provide a dry land bridge

between SA and NA

Panama originated from tectonic rather than volcanic

events


~ 3 myaLate Pliocene, Early Pleistocene migrations

10 bird families to SA, 2 to NA15 mammalian families to SA, 7 to NA

3 survived N of Mexicoopossum, armadillo, porcupine

23 families of other vertebrates to NA, 18 to SA

Biogeoraphic History of Panama

The Great American InterchangeGradual migrations

N => S during periods of coolingStadial periods and Glaciations

S => N during periods of warmingInterglacial and interstadial


Between 3 & 2 myaPleistocene - soon after the migrations began

Extinction of several SA groups Notoungulates



Extinction of several SA groupsNotoungulatesLitopterns



Extinction of several SA groups NotoungulatesLitopternsMarsupial carnivores



Extinction of several SA groups NotoungulatesLitopternsMarsupial carnivoresFlightless birds

Phorusrhacids :Terror Bird



Extinction of several SA groupsNotoungulatesLitopternsMarsupial carnivoresSloths extended far into NA before extinction


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

Biogeography of Panama

Before ~4 myaSA hosted 29 land mammal familiesNA hosted 27 land mammal families58 total families

Soon after the opening of the land bridge22 shared families

7 from NA, 14 from SA, 1 unsureSA: 17 native families confined, NA: 9

Recently15-20ish shared, 11-15 confined to SA, 9 confined to

NA

CA and SA Mammal FamiliesBull-dog Bats, Fish-eating Bats Noctilionidae

Anteaters Myrmecophagidae

Hutias, Nutria Capromyidae*4

Pacas AgoutidaeAgoutis, DasyproctidaeDisc-winged Bats ThyropteridaeNew World Monkeys CebidaeMarmosets, Tamarins CallitrichidaeWest Indian Sloth &Two-toed Tree Sloth MegalonychidaeFunnel-eared Bats Natalidae

Shrew or Rat Opossums CaenolestidaeSmokey Bats FuripteridaeThree-toed Tree Sloths BradypodidaeGuinea Pigs, etc CaviidaeCapybara HydrochaeridaePacarana DinomyidaeChinchilla Rats AbrocomidaeSpiny Rats EchimyidaeOctodonts, Degu OctodontidaeTuco Tucos CtenomyidaeCoypu Myocastoridae*3

CA & SA

SA Only

Pan-American Mammal FamiliesPocket Mice, Kangaroo Rats HeteromyidaePocket Gophers GeomyidaeNew World Porcupines ErethizontidaePeccaries, Javelinas TayassuidaeRacoons, etc ProcyonidaeOpossums DidelphidaeArmadillos DasypodidaeShrews SoricidaeCommon Bats VespertilionidaeDogs, Wolves, Foxes CanidaeFree-tailed Bats MolossidaeWeasels, Otters, Skunks, Badgers MustelidaeBears UrsidaeCats FelidaeSquirrels, Chipmonks, Marmots, Prarie Dogs etc SciuridaeEared Seals, Sea Lions OtariidaeRats, Mice, Voles, Gerbils, Hamsters, etc MuridaeCattle, Sheep, Goats, Antelopes, etc*** BovidaeDeer, etc Cervidae

Hares and Rabbits Leporidae


Biodiversity todaySA is about as species rich as before, but differentNA is less rich, but more similar in compositionBoth achieved maximum density soon after opening of

the bridge and then declined


Marsupial Migrations


Before ~4 myaPanama’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


~3-2 mya Isthmus land bridge used by species

displaced by climatic changes


Names Inter/Glacial Period (kya) Epoch

N. American S. American interglacial present – 12 HoloceneWisconsin Llanquihue glacial period 12 – 110 Pleistocene Sangamonian interglacial 110 – 130 Illinoian Santa María glacial period 130 – 200 Yarmouth interglacial(s) 200 – 300/380 Kansan Río Llico glacial period(s) 300/380 – 455 Aftonian interglacial(s) 455 – 620 Nebraskan Caracol glacial period 620 – 680

Pastonian Stage interglacial 600 – 800Pre-Pastonian Stage glacial period 800 – 1300Bramertonian Stage interglacial 1300 – 1550


TodayAs Panama’s geographic character became

more complex - biodiversity increased Each migrant species passed through Panama

Some stayedSome passed throughSome stayed and sent representatives on

Immigrant species occupied newly developing niches


Panama’s biodiversity today960 bird species220 mammal species240 reptile species160 amphibian species>10,000 vascular plants

All species arrived since Panama aroseAll “native” or “endemic” species arrived

from NA or SA

And the Geological History of Panama Great American Biotic Exchange.

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