Changing Continents and Climates

February 18, 2014

Earth’s Tectonic History• Its hard to overemphasize the effects of plate

tectonics on biogeographic patterns of virtually all organisms

• Paleogeographic reconstructions of Earth’s dynamic history based on 4 lines of evidence:– Paleomagnetic declinations– Symmetrical magnetic stripes of ocean basins– Detailed topographic and bathymetric maps– Lithologic indications of climate

Charles Lyell• Changes in the physical geography of the Earth can

promote or hinder migrations of species• Major climatic changes would cause the movement

(geodispersal) of entire flora and faunas• Geodispersal – the expansion of the range of a group

of species due to the elimination of some topographic or climatic barrier (Lieberman)

• Vicariance: the separation or division of a group of organisms by a geographic barrier, such as a mountain or a body of water, resulting in differentiation of the original group into new varieties or species.

Great American Interchange

• When North and South American became joined 3.5 mya

• More North American species moved into South America

• Exceptions: opossum and armadillo

• High rates of extinction in South America

Great American Interchange

Great American Interchange

Glacial and Post-Glacial Waterbodies

• Pluvial lakes – water bodies that appear with large-scale variations in climate– Great Salt Lake remnant of Lake Bonneville– Glaciers shifted jet stream, which brought more

storms to desert southwest

• Glacial lake (cryogenic lake) – lake filled with glacial meltwater

• Isostatic sea-level changes – changes in sea level caused by depression and distortion of the Earth’s crust by glaciation

• Eustatic sea-level changes – drop in sea level– 80-120m drop in world ocean sea level during the

last glaciation– Beringia and connection of islands to mainlands

Glacial and Post-Glacial Waterbodies

Biogeographic Responses to Glaciation

• Changes in environments:– Changes in the location, extent, and configuration of their

prime habitats

– Changes in the nature of climatic and environmental zones

– Formation and dissolution of dispersal routes

• Responses of biotas:– Some species floated with their optimal habitat

– Some species adapted and didn’t move

– Some species underwent range reduction and eventual extinction