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BILD Compettion - BILD 3 2 May 2008 1 2 What Is a Community...

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BILD 3 2 May 2008 Woodruff: competition 1 1 2 3 What Is a Community? A biological community is an assemblage of populations of various species living close enough for potential interaction Ecologists call relationships between species in a community interspecific interactions Interspecific interactions affect species survival and reproduction Examples are competition, amensalism, predation, herbivory, symbiosis (parasitism, mutualism, and commensalism), and disease 4 AMENSALISM (–/0) Allelopathy, allelochemics 5 AMENSALISM –/0 ALLELOPATHY, ANTIBIOSIS, ALLELOCHEMICS TO PROTECT SPACE WALNUT – JUGLONE: 5-hydroxy-1,4-naphthoquinone inhibits growth of many seedlings MINT (SALVIA) – TERPENES: cineole, camphor COUCH GRASS – PHENOLIC ACID: from roots, inhibits growth of cultivars TO PROTECT TISSUE MILKWEED – cardiac gylcosides, emetic ALKALOIDS: colchicine, nicotine, caffeine, quinine, codeine, mescaline, strychnine 6 INTRASPECIFIC COMPETITION INTERSPECIFIC COMPETITION SCRAMBLE COMPETITION FOR SOME LIMITING RESOURCE Drosophila larvae in culture tube: success determined by initial weight and rate of assimilation. CONTEST COMPETITION FIGHTING, CANNIBALISM, TERRITORIALITY, DOMINANCE Barnacles: Balanus overgrows, undercuts, crushes Chthamalus Chthamalus Balanus
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BILD 3 2 May 2008 Woodruff: competition 2 LE 53-2 Chthamalus fundamental niche High tide Low tide Ocean Chthamalus realized niche High tide Low tide Ocean Balanus realized niche Chthamalus Balanus Balanus INVADES AREA OCCUPIED BY Chthamalus 1 MONTH: 10% C OVERGROWN BY Balanus 3% UNDERCUT 1% CRUSHED 2 MONTHS 20% C ELIMINATED BY Balanus Connell (1961) OBSERVED BARNACLES & INVESTIGATED THEIR INTERACTIONS EXPERIMENTALLY 8 Competitive release Connell (1961) tested by removing one species and measure response of the other Chthalamus upper limit set by dessication, lower limit by Balanus Remove Balanus and Chthalamus speads lower down Remove Chthalamus and Balanus does not invade Balanus upper limit set by dessication, lower limit by starfish predation Remove predators and Balanus extends lower into the sea 9 OUTCOME OF COMPETITION SPECIES 1 WINS SPECIES 2 WINS EITHER WINS - OUTCOME UNPREDICTABLE NEITHER WINS - COEXISTENCE Park's experiments with Tribolium sp. (flour beetles) (N1, N2) N1 N2 N1 wins N2 wins at 24 o , 70% RH N1 wins N2 wins cool, dry hot, humid ? 10 Competition Interspecific competition occurs when species compete for a resource in short supply Strong competition can lead to competitive exclusion, local elimination of a competing species Intraspecific competition (especially for mates and often resulting in sexual selection will be discussed later in the course 11 The Competitive Exclusion Principle
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