1PredationCompetitionSpecies interactionsSpecies interactions?23Pairwise Species Interactions• Competition (interspecific) (-, -)• Predation, herbivory, parasitism (+, -)• Mutualism (+, +)• Amensalism (0, -)• Commensalism (0, +)d humans / d cattle = ?Interspecific Interactions: Effect of individuals on other individuals (orof populations on other populations) of different species4True predators - many hosts- always lethal552.2152.196 Grazers - many hosts- rarely lethal71437 nmParasites- one or few hosts- rarely lethal8Parasitoids - one host - always lethal910Functionaldefinitions:1153.1 53.112LE 53-2Chthamalusfundamental nicheHigh tideLow tideOceanChthamalusrealized nicheHigh tideLow tideOceanBalanusrealized nicheChthamalusBalanus13Connell’s experimental demonstration of asymmetric,exploitative competition between barnacle species forspace, a limiting resource.BalanusChthamalusSpace--- -++Remove Balanus, Chthamalus spreads into lower intertidal.Remove Chthamalus, Balanus does not spread upwards.1453.253.2Balanus’ upper limit determined by physical stress;Chthamalus’ lower limit determined by competitionwith Balanus15Moreasymmetriccompetitonbetweenciliateprotozoans163 Types of Competition (-,-)• Exploitative: two species competefor a resource that is limiting: inshort supply relative to theirneeds indirect• Interference: two speciesdirectly harm each other by toxicallelochemicals, injury or wastingtime, increasing risk, etc. direct• Apparent: two species decrease ineach other’s presence becausethey support the increasedabundance or vigor of a commonpredator indirect+ +- ---+ +--17ACBCompetitionfor a commonlimitingresource(Exploitation)BADCompetition mediatedby increasing risk froma common predator(Apparent competition)18Wild salmonHuman fishersSeals, ternsIndirect interaction: Apparent competition--+- (+)+-Hatchery salmon19Evolutionary consequences of competition:Niche partitioning, character displacementNumber consumedSeed size20Partial niche overlap: competition for seeds ofintermediate sizeSpecies 1Species 2Number consumedSeed size21Finch species oncecompeted for seeds,but natural selectionfor “characterdisplacement” reducedcompetition forsympatric (co-occurring) populationsFinch AFinch BSeeds- -- -++Finch A Finch B--++LittleSeedsBig Seeds- -++22Mutualism• Mutualism is a type of interaction that isbeneficial to both species involved.• It may be obligate or facultative.• It may be symbiotic or non-symbiotic.23Cleaning,guiding,etc.24Clown fish live in mutualisticsymbiosis with sea anemone• Clown fishmucusprotects itfromanemonesting, andclown fishfeedingimportscrumbs thatfeed anemone253 species interactions: Mutualists and cheaters…. Cleaner wrasses, host fish, cheaterblenniesMilkweed, bee, cheater orchidPollinator, moth, bumblebee nectarburglarSelection for refinement of cuesand mimicry in co-evolutionary raceHow much cheating can be toleratedbefore mutualism breaks down?26Pollination mutualisms27Gut microbes allow termitesand cows to digest cellulose28Higher plants and fungi - mycorrhizae29Zooxanthellae(algae) in coralsCoralbleaching:loss ofalgae30Fungi and algae - lichens31MoistureLightWithoutfungalmutualistdrywetWith fungal mutualistAn algaparticipatingin a symbioticmutualismwith a fungusAs a lichenmay have itsrealizednicheexpanded andshifted bytheinteraction…Lichen = mutualistic (+,+) associationof algae (fixes energy) and fungi (protective cover)Symbiosis = 2 species living togetherAlgal Niche…32Nitrogen fixation(cyanobacteria, Rhizobium bacteria inlegumes, alders, diatoms)33Charlene NgCharlene NgRex LoweN234Mutualism (+,+) leaf cutter ants (Atta spp)culture fungi (Ignacio Chapela, ESPM)Mark Moffett photos35Culture of crops or livestock36MinorsdefendworkersfromparasiticphoridfliesHerbivory/fungivory: leaf cutter ants37Fungal garden inundergroundchamber of antcolonyYoung queen carries bitof fungus to start newcolony38Mutualisms (+,+)39Extrafloralnectarieson Acaciafeed antsthatprotect theAcaciatrees fromherbivoresand vines40Species
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