South America

Front 1

Gondwana

Back 1

- Was originally part of Gondwana, along with New- Guinea, Africa, India, Madagascar and Australia. Taxonomic rel between large seeded tree taxa- Gondwana distribution. However, other taxa such as Ficus suggest that intercontinental lineages diverged long after continents, owe range to modern colonisation.

Front 2

33Ma

Back 2

cooling- Boreotropical elements moved to south of North American Plate, eventually reached South America following formation of Panama Isthmus. Some shared taxa have limited modern distributions such as Bonnetiaceae, found in Malesia and Guyana Shield.

Front 3

Tapirs and Hummingbirds

Back 3

- Tapirs reached N. America from Asia, made their way down to South America later. Modern Hummingbirds have an exclusively European pre-Pleistocene fossil record.

Front 4

cretaceous

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- Limited contact btw n and s America occurred during cretaceous, allowing interchange of some dinosaurs, reptiles and plants. Rate of interchange increased as continents grew closer. Some immigrants from north diversified rapidly after reaching south America.

Front 5

Panama isthmus

Back 5

bridged the two continents 3-4 million years ago. South American mammal families rose from 32 to 39 and back down to the current 35. Immigrants included peccaries, bears, cats, coatimundis, dogs, deer, tapirs, shrews, squirrels and (now extinct) mastodonts and American horses. - Capybaras, porcupines, agoutis, spiny rats, monkeys, tamarins and (extinct) glyptodonts moved north.
- No evidence for displacement of south American lowland plants by northern immigrants.
- Geologically recent, colonisation processes still underway. Freshwater fish slow to move. Some species show northern biased diversity pattern in south American forests such as Coryphoidae palms.

Front 6

Ridges

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- Ridges may have existed btw South America and Africa up until Oligocene, when Atlantic ridge islands were above water. Islands on dynamic plate fragments may explain how some marine-intolerant freshwater fish moved between south and north America prior to land bridge formation.

Front 7

Africa and S. Am

Back 7

- Africa and south America broke physical contact 96Ma, Atlantic ocean widening ever since. 1/5th of 1,104 tree spp in 25ha plot in Ecuadorian Amazon believed to belong to families and genera that arrived from Paleotropics since S. America became discrete land mass. Widespread example is Symphonia globulifera, first colonised S. america’s forests from Africa 17ma. Some transfers have been west to east. Bromeliaceae and Cataceae are diverse in Americas, but have single species in Africa. Twelve angiosperm families and 110 plant genera straddle Atlantic- distributions limited to American and African tropics. Given sufficient time, even extremely unlikely events become increasingly probably. Strong winds plausible dispersal force for seeds. Birds can be blown far from migration routes. Transfers may have benefitted from mid-oceanic land, might have had forest.

Front 8

Rafts

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- Rafts of buoyant vegetation- may explain why monkeys and rodents reached S. America from Africa during Oligocene and Miocene, when Atlantic was half its current breadth.

Front 9

last 60my

Back 9

• Wet island last 60my. Modern Amazonian genera present by late Miocene. Climate, mountain building, changes in water cover and spp exchange

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low alluvial basin

Back 10

• Low alluvial basin- prone to flooding and readily shifting rivers. Basin probably submerged occasionally by FW and marine incursions since Cretaceous. Originally flowed westward. 40ma, protoandes dammed flow, created shallow lake, drained NW then to east. 10-6ma, FW wetland, sea levels high, shallow sea to Caribbean- amazon’s rich river fauna incl FW dolphins, stingrays, needlefish, Caribbean origin.

Front 11

rising andes

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diversification, many related taxa on both sides, but become distinct spp.

Front 12

Grasslands 32ma

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, not to extent of Africa. Various large mammals proliferated, remained absent from forests.

Front 13

Atlantic strip SE Brazil

Back 13

• Atlantic strip of SE Brazil captures moisture- patchy RF rich in endemic spp. Half of tree spp also occur in Amazon or elsewhere in Americas- periods of extensive forest cover.

Front 14

Central America forests

Back 14

affinities to Amazon guyana and pacific forests

Front 15

west of andes

Back 15

lush pacific coast rf shares many genera w amazon also endemics