Competitive Exclusion.doc

"Competitive Exclusion? Theory ? First theorized 1920?s-30?s ? Restated 1960 by Garrett Hardin ? Assumes a uniform habitat unchanging over time ? A few superior species should dominate ? Other species out-competed & go extinct ? Would explain Challenger findings ? Sanders & Hessler 1960s (epibenthic sled) ? Many more species (burrowers as well as swimmers) ? Number of individuals decreases with depth ? But less decline in species diversity then seen before ? Grassle 1970s - 1980s (box corer) ? Still observed fewer organisms at greater depths ? Many new species: diversity increased with depth ? Probably did not find all species that were there ? Evidence that contradicts ?competitive exclusion? Summary II: 1960s - 1970s "Stability-Diversity" Theory (?70s) ? Constancy of environment over a long period of time ? Allows evolution of new species without forcing extinction of old species ? Organisms adapt to each other as well as to the environment ? Would explain Sanders & Hessler findings ? Has not been disproven but is no longer the favorite theory Oceanography 102, Nuwer/Strickland Lecture 9 © 2010 University of Washington 36 "Scarce Resources" Theory ? Scarce resources favor biological innovation and diversification ? Plentiful food: little advantage for a mutation that creates an alternative feeding niche ? Scarce food: advantage for a mutation that creates an alternative feeding niche ? Coral reefs very diverse despite scarce resources ? Would explain Grassle findings ? Has not been disproven but is no longer the favorite theory