Gigantism and the Island Rule

Tim Schmidt

Questions

What caused the extinction of gigantism (Pleistocene megafauna)?

What are the causes behind the island rule?

Is there a link between the extinction of gigantism in animals and the “island rule”?

Gigantism (Pleistocene megafauna)

Mega Fauna = Big animal

Pleistocene era ended around 12,000 years ago with recession of last continental glacier

Environmental Changes

Overhunting

journal.davidbyrne.com

Megafauna vs. Humans

(Barnosky, 2008)

Irish Elk

http://tembotime.files.wordpress.com/2011/03/irish-elk.gif

• Known for large antlers•Used for fighting (Only in males)•Antlers could reach 3.6 m and weigh almost 40 kg•Change of environment led to lack of nutrients (Calcium)•Could no longer afford antlers energetically•Human hunting•http://farm3.static.flickr.com/2222/2146772919_f9461a59d8.jpg

Moose vs. Irish Elk

(Moen, Pastor, & Cohen, 1999)

Island Rule

http://online-show.com/wp-content/uploads/2010/05/tropical_island_screensaver1.jpg

•Small vertebrates - Gigantism•Competitive Release

•Large vertebrates - Dwarfism•Lack of nutrition•Increased competition•New predators

Case Study (Lomolino, 2005)

Conclusion

Similarities between Extinction of Megafauna and Island Ruleo Both have nutritional constraintso New predator relationshipso Increased competition

Works Cited Barnosky, A, D. (2008). Megafauna biomass tradeoff as a driver of quaternary and future extinctions. PNAS,

105(1), 11543–11548.

Lomolino, M.V. (1985). Body size of mammals on islands: the island rule reexamined. The American Naturalist, 125(2), 310-316.

Lomolino, M.V. (2005). Body size evolution in insular vertebrates: generality of the island rule. Journal of Biogeography, 32, 1683-1699.

 McClain, C.R., Boyer, A.G., & Rosenberg, G. (2006). The island rule and the evolution of body size in the deep sea. Journal of Biogeography, 33, 1578-1584

 Meiri, S., Dayan, T., & Simberloff, D. (2004). Body size of insular carnivores: little support for the island rule. The American Naturalist, 163(3), 469-479.

 Millien, V., & Damuth, J. (2004). Climate change and size evolution in an island rodent species: new perspectives on the island rule. Evolution, 58(6), 1353-1360. 

Moen, R.A., Pastor, J., & Cohen, Y. (1999). Antler growth and extinction of irish elk. Evolutionary Ecology Research, 1, 235-249.

 Raia, P., & Meiri, S. (2006). The island rule in large mammals: paleontology meets ecology. Evolution, 60(8), 1731-1742.

Questions?

http://www.anaspides.net/images/anaspides_net/earth_life_sciences/megafauna_extinction/m_prisca_and_friend.jpg