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Lecture Outline Definitions and Predictions Types of Exchange Between Partners Examples Exploitation of Mutualisms Examples Stabilizing Mechanisms Case Study: What is the difference between a parasite and a mutualist? Symbiosis (Greek: with life) An intimate and exploitative, neutral, or beneficial interaction between different species Mutualism A reciprocally beneficial interaction between different species Cooperation or mutual exploitation? Continuum of Interactions (-,+) (o,+) Predation Parasitism Commensalism (o) = no net gain or loss (neutral) (+) = net gain (beneficial) (-) = net loss (exploitative) (+,+) Mutualism Species 1 Population Size Population Trajectories With and Without Mutualism With Species 2 Without Species 2 Species 2 Population Size Time With Species 1 Without Species 1 Time Obligate Mutualism Species 1 Population Size Population Trajectories With and Without Mutualism Positive Interaction Coefficient dN1 r1N1 (K1 − N1 + α12 N 2 ) = K1 dt Species 2 Population Size Time dN 2 r2 N 2 (K 2 − N 2 + α 21N1 ) = K2 dt Time Mutualism Categories TRANSPORT What is exchanged? Plant-pollinator Plant-dispersal PROTECTION NUTRITION Ant-acacia Gut symbioses Lichens Plant-fungal mycorrhizae Plant-fungal endophytes Plant-rhizobia Marine-dinoflagellates Eukaryotes-organelles Pollination Mutualism nutrients pollinator angiosperm gamete transport Seed Dispersal Mutualisms seed transport Disperser fruit carbohydrates QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Angiosperm QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Endosymbiosis: a protist-algal mutualism photosynthate Vorticella phagocytosis protist Chlorella green alga essential mineral nutrients endosymbiosis Leaf Cutter Ants and Fungal “Farms” nutrition Ants nutrition Fungi QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Atta mexicana Fungal mycelia consuming harvested foliage Lichen: Fungi and Green Algae or Cyanobacteria fruticose protection Fungi Algae carbohydrates thallus cross-section Fungal Endophytes and Plants nutrition Cacao pathogen defense nutrition Endophyte QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Theobroma cacao Arnold et al (2003) herbivory defense Grasses QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Festuca Clay (1988) When Mutualisms Get Ugly… Beneficial interactions are susceptible to exploitation from inside and outside the interaction (+) Species 1 Species 2 (+) Cheating from inside interaction Exploitation from outside interaction Arboreal Ants and Whistling Thorn Acacia in Kenya Defense leads to parasitism QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Ants (+) shelter and nutrients Acacia (-) Acacia drapanolobium C. mimosea C. sjostedti C. nigriceps T. penzigi QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. vulnerable to canopy take-over 40% increase branch in production causes tree sterilization, but reduces lateral contact with other trees Stanton et al (1999) Shift to Predation Excess sugar Predation (8x) carbohydrate (+) Ants Aphids (+,-) Waste removal, predator protection QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Offenberg (2001) Algal Infection and Release medusa ephyra Free algae Infected polyps Uninfected polyps Sachs and Wilcox (2006) Does infection mode influence mutualism? Free algae Vertical transmission Horizontal transmission Sachs and Wilcox (2006) Measure Host and Symbiont Fitness HOST FITNESS Reproduction (count buds) Polyp growth rate SYMBIONT FITNESS Reproduction (expulsion rate) Algal density within host Sachs and Wilcox (2006) Symbiont Reproduction Algae faces tradeoff Maximizing algal reproduction reduces host growth rate and expulsion Host Growth Rate Shift to parasitism limits spread of algae to new host Cleaner and Client Fish Mutualism: Partner Choice Simulation “Resident Client” 2nd QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. 1st “Choosy Client” The cleaner fish maximized food intake in all trials and identified the “choosy client” option after 1 simulation Bshary and Grutter (2002) If mutualism fails in one population, other cooperating populations can repopulate (+,-) (+,+) (+,-) (+,-) (+,-) (+,-) (+,+) (+,-) (+,-) (+,+) (+,-) (+,-) (+,-) (+,+) Extinction (+,+) (+,+) (+,+) (+,+)(+,+) (+,-) (+,+) (+,+) (+,+) (+,-) (+,+) (+,+) (+,+) Success Thompson (2005) Summary of mutualism stabilizing mechanisms Vertical Transmission Restrictions to Fitness QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Partner Choice Repeated Interactions QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Restrictions of Options QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Alignment of Interests QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Colletotrichum spp. UV Wildtype: Pathogen 100% lethal to host plant Mutant: Commensal No effect on host plant UV Mutant: Mutualist Benefits host plant Redman, Dunigan, Rodriquez 2001 Plants Colonized by Mutualist Strain Have: increased resistance to wildtype strain QuickTime™ and a TIFF (LZW) decompressor are needed to see this picture. increased drought resistance increased growth Redman, Dunigan, Rodriquez 2001