by the giant glaciers bearing down the temperate areas. Evidences from geomorphology, paleobotany and biogeography indicate dramatic changes in Amazonia during the Ice Age.

Neotropics became cooler and drier with the glacial advances in Northern Hemisphere, altering and shifting ecosystems. Grasslands, savannahs and cerrado areas enlarged, rainforests diminished and fragmented in "forest islands" surrounded by "seas" of savannah or dry woodland. Populations became periodically isolated from each other in this varying-sized, shrinked rainforest islands, promoting speciation.

Even during the driest, coolest periods, it is believed that some areas persisted as rainforest where rainfall remained high, isolated from each other by wide extensions of grassland. The refuge regions may have been subject to different natural selection pressures, promoting rapid genetic divergence among isolated populations.

Forests then expanded during interglacial periods, establishing secondary contacts between the newly speciated populations. This repeated shrinkage and expansion is an explanation to so many extremely similar species in Amazonia.

text based on
"A Brief Evolutionary History of South America" - Arto Ovaska - http://www.cbc.org.pe/manuvilca/

And what about Pantanal?

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A Very Brief
Evolutionary
History of
South America

Jurassic Period, Mesozoic Era. The future South America´s land mass is united
to the ones to become Africa, Madagascar, Australia, New Zealand, Antarctica and
India, inhabited by dinosaurs.

The breakup of this gigantic land, known as Gondwana, begun about 120 million years ago, during earnest Jurassic, continuing throughout Cretaceous Period that closes Mesozoic Era approximately 65 mya, and is still going on.

Remaining as an isolated continent during most of Cenozoic Era, South America pleased the evolution of many unique groups of creatures. Among the mammals were the opossums, the extinct Gliptodont - kind of giant armadillo -, the Megaterium giant land sloth and the Scelidotherium giant anteater, besides their today´s remaining relatives.

During mid-Cenozoic Miocene appeared new creatures as monkeys (1st fossil record 26 mya) and rodents as capybaras and porcupines (1st fossil 34 mya), perhaps dispersed over water in floating vegetation 'rafts' coming from Africa - that was still relatively close - or from North America.

Just prior to the start of Ice Age (Pleistocene Period), North and South America became linked by the Panamanian land bridge, an isthmus that came about because of the uplifting of northern Andes combined to a global drop in sea level due to polar ice caps increasing.

Some Southern animals moved northwards about 2,5 mya, including 2 armadillo species and the glyptodont, 2 species of ground sloths, a porcupine, a large capybara, opossums, and the Phororharcos inflatus, a 3 mt tall not-flying bird, shaped as kind of a 'rapine' ostrich. Among these, only armadillos and opossums remain.

In contrast, many more North American animals walked across the land bridge with a much greater impact in South america. The list is wide-range including skunks, peccaries, horses, dogs, saber-toothed cats, other cats, tapirs, camels, deers, rabbits, tree squirrels, bears, and maybe field mice and cricetid rodents (the 2 last ones still under debate). The outcome of this was that South American fauna became much more like the North american one.

The Great American Interchange of Species started with Pleistocene Period, which begun about 2,5 mya and ended just 10.000 ya (Holocene), increasing the speciation rates.

Equatorial tropics became climatically unstable during Pleistocene, influenced by the giant glaciers bearing down the temperate areas. Evidences from geomorphology, paleobotany and biogeography indicate dramatic changes in Amazonia during the Ice Age.

text based on
"A Brief Evolutionary History of South America" - Arto Ovaska - http://www.cbc.org.pe/manuvilca/

And what about Pantanal?

> LOGBOOK > INFO > TOURS > MAP > GALLERY > RESERVATION > CONTACT