Species interactions Competition Predation 1 2 Pairwise Species Interactions Interspecific Interactions Effect of individuals on other individuals or of populations on other populations of different species Competition interspecific Predation herbivory parasitism Mutualism Amensalism 0 Commensalism 0 True predators many hosts always lethal d humans d cattle 3 4 Grazers many hosts rarely lethal 52 19 52 21 5 6 Parasitoids one host always lethal Parasites one 1437 or nm few hosts rarely lethal 7 8 Functional definitions 9 10 LE 53 2 Chthamalus Balanus High tide High tide Chthamalus realized niche Chthamalus fundamental niche Balanus realized niche Ocean 53 1 53 1 11 Low tide Ocean Low tide 12 Remove Balanus Chthamalus spreads into lower intertidal Remove Chthamalus Balanus does not spread upwards Balanus upper limit determined by physical stress 53 2 53 2 Chthamalus lower limit determined by competition with Balanus Connell s experimental demonstration of asymmetric exploitative competition between barnacle species for space a limiting resource Chthamalus Balanus 13 Space 14 3 Types of Competition More asymmetric competiton between ciliate protozoans 15 Exploitative two species compete for a resource that is limiting in short supply relative to their needs indirect Interference two species directly harm each other by toxic allelochemicals injury or wasting time increasing risk etc direct Apparent two species decrease in each other s presence because they support the increased abundance or vigor of a common predator indirect 16 Indirect interaction Apparent competition A B D C Competition for a common limiting resource Exploitation A Human fishers Seals terns B Wild salmon Hatchery salmon Competition mediated by increasing risk from a common predator Apparent competition 17 18 Evolutionary consequences of competition Niche partitioning character displacement Partial niche overlap competition for seeds of intermediate size Species 1 Number consumed Number consumed Species 2 Seed size Seed size 19 Finch A Finch B Mutualism Seeds Finch species once competed for seeds but natural selection for character displacement reduced competition for sympatric cooccurring populations Finch A Little Seeds Mutualism is a type of interaction that is beneficial to both species involved It may be obligate or facultative It may be symbiotic or non symbiotic Finch B Big Seeds 20 21 Cleaning guiding etc 23 22 Clown fish live in mutualistic symbiosis with sea anemone Clown fish mucus protects it from anemone sting and clown fish feeding imports crumbs that feed anemone 24 3 species interactions Mutualists and cheaters Cleaner wrasses host fish cheater blennies Milkweed bee cheater orchid Pollination mutualisms Pollinator moth bumblebee nectar burglar Selection for refinement of cues and mimicry in co evolutionary race How much cheating can be tolerated before mutualism breaks down 25 26 Gut microbes allow termites and cows to digest cellulose Higher plants and fungi mycorrhizae 27 28 Coral bleaching loss of algae Zooxanthellae algae in corals 29 Fungi and algae lichens 30 Lichen mutualistic association of algae fixes energy and fungi protective cover Algal Niche With fungal mutualist Light dry Moisture Without fungal mutualist wet An alga participating in a symbiotic mutualism with a fungus As a lichen may have its realized niche expanded and shifted by the interaction 31 Symbiosis 2 species living together 32 Mutualism leaf cutter ants Atta spp culture fungi Ignacio Chapela ESPM Charlene Ng Rex Lowe Nitrogen fixation cyanobacteria Rhizobium bacteria in legumes alders diatoms N2 Charlene Ng 33 Mark Moffett photos 34 Herbivory fungivory leaf cutter ants Minors defend workers from parasitic phorid flies Culture of crops or livestock 35 36 Fungal garden in underground chamber of ant colony Mutualisms Young queen carries bit of fungus to start new colony 37 38 Species interactions Extrafloral nectaries on Acacia feed ants that protect the Acacia trees from herbivores and vines 39 40
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