Why Study Paleoecology? -- how and why communities change -- causes of extinctions, development of modern communities -- predict future changes

Grand Canyon, AZ

Fossil remains mummify and preserve quite well in dry caves

California Condor once nested in Grand Canyon caves

Gymnogyps californianus Radiocarbon date of 12,540 B.P. Gymnogyps californianus (California Condor)

Condors have been successfully reintroduced to Grand Canyon, nesting again for first time in 10,000 yrs

Problems with fossil record -- Preservation varies soft parts usually don’t preserve exceptions in ice, bogs, amber -- Mode of deposition important stream deposits accumulate fossils caves preserve cave-dwelling species natural traps -- Behavior of species important caves and natural traps again

Taphonomy: Uniformitarianism: -- understanding the history of deposition Uniformitarianism: -- physical processes of today (weathering, stream flow, erosion) are the same as in the past

Giant Armadillo

Fossil Assemblages can be: -- Biocoenose: represent a true community from the past -- Thanatocoenose: not a true community, but an assembly of species associated only in death, or only in fossil deposit What would be the ideal fossil site?

Bushy-tailed Woodrat

woodrat midden

The Last Glacial Maximum (LGM) at ~18,000 B.P. jan.ucc.nau.edu

Changes in pinyon tree distribution since the Ice Ages

Disharmonius or Non-analog Faunas

Mixed or non-analog plant and animal communities characterize the late Pleistocene in North America Species assemblages with no modern analogy, usually composed of taxa that occur in warm and cold climates that are not found together today e.g., lemmings in cave faunas in the western U.S. along with desert rodents, or snowy and hawk owls with vultures and sage grouse This pattern was probably due to mild winters and cool summers that characterized post-LGM climates

Loss of megafauna and keystone species would have had a dramatic impact on plant and small mammal communities www.news.wisc.edu By the end of the Pleistocene at 10,000 B.P., over 30 genera of large mammals became extinct Small mammals (< 5 kg), however, suffered few or no extinctions Modern communities were well established by 6000 B.P.

Cement Creek Cave, Colorado (elev. 2950 m or 9500 feet)

All sediments were screen washed, dried, and sorted for bone

Thousands of small mammal bone fragments and teeth, especially from voles and other rodents, have been recovered. Possibly due to use of cave by weasels; numerous weasel bones in fossil assemblage.

Shrub-ox (Euceratherium collinum) wickipedia.com Euceratherium Shrub-ox (Euceratherium collinum) Browser that fed primarily on trees and shrubs, especially sagebrush, rabbitbrush, acacia, oak (Kropf et al. 2007) 22

Sagebrush Vole (Lemmiscus curtatus) thehandfordproject.com Lemmiscus Sagebrush Vole (Lemmiscus curtatus) Primarily feeds on flowers, bark, twigs of sagebrush, plus lots of grasses, forbs, and woody plants (Fitzgerald et al. 1994) 23

Current sagebrush habitat near Gunnison, with dense stands of sagebrush and grasses Modern steppe has more grasses, forbs, especially bunch grasses mixed in with sagebrush

Rancho la Brea Tar Pits, CA George C. Page Museum

Dire Wolf skulls

Paleobiology of Sabretooth cat based on functional morphology

What happened 10,000 years ago? -- mass extinctions worldwide -- targeted mainly large mammals -- 33 genera of ‘megafauna’ disappear -- marine life, plants largely unaffected Pleistocene Overkill Hypothesis -- proposed by Paul Martin in 1960s -- extinctions correlated with human population expansion -- hunted large mammals, arrived in NA at ~12,500 years ago -- testable, controversial hypothesis that is still valid

Names to know for final exam: know their major contributions to ecology, significance of their work. Robert MacArthur Charles Krebs Jane Lubchenco Joseph Connell G. F. Gause Margaret Davis Paul Martin C. H. Merriam Paul Ehrlich