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Lecture 7

Biology Lecture 7 Article 5.docx

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Scott Browning

BIOLOGY LECTURE 7 Keystone Species Structure o Maintain the structure and integrity of the community (Summary)  Play a disproportionately large role in prevalence + pop lvls of species in the community  Recovery of graywolf shows imp of keystone species in long-term stability  * Preservation + restoration of keystone species needed for maintaining/reestablishing structure + function of eco they inhabit Paines Milestones: STARFISH = TOP PRED + KEYSTONE  Robert Paine: examining the interaction strengths of food webs in rocky intertidal ecosystems  Study site 1: community consistently dominated by same species of mussels, baracles, and starfish (top pred)  Diversity declined as # of preds decreased, so consumers might be have a greater role than others in controlling the # of species coexisting in these communities  Experiment: “Typical” piece of shoreline kept free of starfish compared to undisturbed control area of equal size  Removal of Pisaster starfish = dramatic changes in temperate intertidal  Remaining members immediately competed with each other to occupy limited space + resources  3 months after, Balanus Glandula barnacles were 60-80% of available space  9 months after, replaced by fast growing pops of Mitella barnacle and Mytilus mussel.  Continued until less and less species occupied area and it was dominated by Mytilus and some Mitella  Sucession of species wiped out pops of benthic algae  Limpet emigrated because of lack of food/space  1 year later, diversity decreased in study area from 15 to 8 species  Effect of removal of top predator on total species # in intertidal Starfish = keystone species community’s structure and integrity, and unaltered persistence  Keystone species have a TD influence on lower trophic levels and stop species at lower levels from monopolizing critical resources, like competition for space or key producer food Other Keystone Species  Other exa
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