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10/26/2009 Mutualisms Effect on big species Effect on small species + 0 - + Mutualism Commensalis m Exploitation (Disease, Parasite) 0 N/A No interaction N/A - Exploitation (Predation) Amensalism Competition 1 Examples of mutualisms 2 Two degrees of mutualism Obligate Facultative 3 Each species needs the other to live Usually live in very tight physical proximity Often called symbiosis (living together) Each species can live without the other 4 1 10/26/2009 Mutualism evolution How can mutualisms evolve? Must have benefits>costs (net fitness increase) Comparative advantage sets up potential for each to benefit Some of my work Plants good at C, fungi good at N, P Still Prisoner’s Dilemma applies Almostt always Al l better b tt tto ttake k without ith t giving i i Kin selection not a possibility! Some become by-product EG bees carry pollen around for their own purposes (eating) – cross-pollination accidental Many are reciprocal 5 6 Mutualism – the forgotten interaction Mutualism as barter Three categories of mutualism Resources include food, carbon, minerals, water Resource-service Resource-resource S i Services include i l d transportation t t ti and d defense d f Life is Lif i impossible i ibl without ih mutualisms li But it received much less attention than competition & predation Is this due to the historically larger number of men? men?.... Service-Service 7 8 2 10/26/2009 Mutualisms – the tour Resource-Resource Mycorrhizae Rhizobium Coral/Zooxanthellae Gut symbionts Pollination Phagophily/Defense Zoochory (seed dispersal) Farming Service-service Facillitation Endosymbiosis 9 >400 million years old >80% of plant species Life as we know it would not be same w/o Plants on land may have been a result Nearly all mushrooms on forest floor are just the reproductive bodies of mycorhiza Ericoid, orchid, other 10 11 One group fungi, but many plants (incl. crops) E t Ectomycorrhizae hi A plant can give up 10-50% of its photosynthesis to Mycorrhizae Fungi: ? Fungus penetrates plant root Arbuscular (most common) Plants photosyntesize, good at C/Sugar/Energy Service-service Facillitation Endosymbiosis Endomycorrhizae The trade: Pollination Phagophily/Defense Zoochory (seed dispersal) Farming Types of mycorhiza Plant-fungus Plant fungus Mycorrhizae Rhizobium Coral/Zooxanthellae Gut symbionts Resource-service Mycorrhiza Resource-Resource Resource-service Mutualisms – the tour Form sheath around the root Many fungal groups, but few plant groups: Oaks, pines, birch, eucalypt rose 12 3 10/26/2009 Water So what do fungi give plants? 13 14 Willing to commit homicide for a friend Mineral nutrition: N & P Fungal hyphae Cover much more area (very fine) Are better at active pumping of N & P Radioisotope N&P can travel 30+m through mycorrhizae One common species of mycorrhizae (Laccaria bicolor) actually kills and eats soil “insects” (springtails) to provide extra nitrogen Known that springtails eat mycorrhizae 15 Study to see which fungus they like best When fed L. bicolor, the eaters ended up d d dead L. bicolor exudes a parasitic toxin and then puts hyphae into the spring tails to dissolve them Some trees get >25% of their nitrogen from this 16 4 10/26/2009 Bioremediation Fairweather friends? Mycorrhizae from high nutrient soils appear to give less nutrients, less benefit Other studies have shown plants will drop their mycorrhizae when fertilized When replanting trees Forestry Mining Don’t just plant trees Innoculate soil http://mycorrhizas.info/roles.html 17 Mutualisms – the tour Mycorrhizae Rhizobium Coral/Zooxanthellae Gut symbionts Provides Oxygen While keeping anaerobic environment for nitrogenase to work Allocate less oxygen to nodules that don’t produce Important to humans 19 N2 + 6 H + energy → 2 NH3 Take N out of air to plant available form Get sugar back (obligate) Plants produce leghaemoglobin Detects legume proteins, release chemical that promotes nodule formation Create enzyme nitrogenase Pollination Phagophily/Defense Zoochory (seed dispersal) Farming Service-service Facillitation Endosymbiosis Rhizobia are g gram-positive p bacteria Live in root nodules of legumes Resource-service Rhizobium Resource-Resource 18 Crop rotation bean/wheat/corn Bean trees key source of nitrogen in the desert 20 5 10/26/2009 Coral Mutualisms Mutualisms – the tour Resource-Resource Stressed corals expel the zooxanthallae Turn white Even if recover, it takes weeks-months before return Overheating one cause – global warming … Corals also very sensitive to CO2 acidification (calcerous skeletons) 21 22 Hard to digest Who you going to call? Mycorrhizae Rhizobium Coral/Zooxanthellae Gut symbionts Bacteria! Ruminants Pollination Phagophily/Defense Zoochory (seed dispersal) Farming Service-service Facillitation Endosymbiosis Bleaching Resource-service Corals induce release of organic compounds with “signal compounds” that alter permeability of zooxanthallae cell membrane. Corals also control rate of zooxanthallae population growth and density by influencing organic matter secretion. Resource-Resource Photosynthesis for nitrogen (hydra are predators) No cheating! Pollination Phagophily/Defense Zoochory (seed dispersal) Farming Service-service Facillitation Endosymbiosis A hydra (upside down jellyfish) that secretes hard skeleton Zooxanthallae algae live inside Mutualisms – the tour Coral Resource-service Mycorrhizae Rhizobium Coral/Zooxanthellae Gut symbionts 23 Cows, goats, sheep, deer, buffalo, antelope (not horses) 4 stomachs Cud chewing Bacteria break down cellulose via fermentation (anaerobic – no oxygen) in rumen Bacteria that move into small intestine are in turn digested 24 6 10/26/2009 Other gut symbionts Humans Lichens 500-1000 species in gut Different species at different locations down the intestine Escherica coli common Can turn bad with virulent strains, weakened immune systems Termites digest wood Black smoker vents Not necessarily gut Bacteria eat sulfates 25 26 Mutualisms – the tour Mycorrhizae Rhizobium Coral/Zooxanthellae Gut symbionts Resource-service Pollination Resource-Resource Pollination Phagophily/Defense Zoochory (seed dispersal) Farming Service-service Facillitation Endosymbiosis Algae/fungi Photosynthesis/minerals Tightly symbiotic Reproductive structures have both algae & fungi (travel together) Food F d ((nectar, pollen) ll ) for f transport Much more efficient than wind/water Generalist specialist spectrum Generalist-specialist 27 Some plants highly coevolved to just one pollinator Others will take bees-birds-bats Saguaro 28 7 10/26/2009 The Yucca Moth and the Yucca Pollination syndromes Color Scent Other Bees Yellow, blue Y Ultraviolet nectar guides Bowl or zygomorphic Butterflies Pink/ lavender?? Y Tubes for long tongues Landing platforms Moths White (night) Y Flies BrownOrange Flesh/rotting The yucca/yucca moth relationship is obligatory (the moth larvae have no other food source and the yucca plants have no other pollinator): Bats White (night) Y Bowl shaped, large Birds Red N Tubular 29 Many of the “specialized” traits are really preadaptations adult female yucca moths carry balls of pollen between yucca flowers by means of specialized mouthparts during pollination, the female moth deposits eggs in the ovary of the yucca flower after the eggs hatch, the developing larvae feed on some of the developing yucca seeds, not exceeding 30% of the seed crop the yucca exerts selective pressure on the moths (through abortion of heavily infested fruits) to limit moth genotypes predisposed to lay large numbers of eggs (cheaters) 30 Mutualisms – the tour Resource-Resource Resource-service 31 Mycorrhizae Rhizobium Coral/Zooxanthellae Gut symbionts Pollination Phagophily/Defense Zoochory (seed dispersal) Farming Service-service Facillitation Endosymbiosis 32 8 10/26/2009 Ants and Bullhorn Acacia Parasite cleaning Several marine systems Cleaning stations Wrasses & gobey’s Big fish line up Saber toothed blenny Saber-toothed Herbivores attempting to forage on accacia plants occupied by accacia ants are met by a large number of fast, agile, highly-aggressive defenders. Ant Benefits: Does the dance Takes a big bite Some birds as well 33 Grow better, survive longer, fewer insects, but don’t trust them with the baby 35 Thorns provide living space. Folliar nectaries provide sugar. Beltian bodies are a source of oils and protein. 34 Ant/sunflower in the temperate zone 36 9 10/26/2009 Mutualisms – the tour Resource-Resource Mycorrhizae Rhizobium Coral/Zooxanthellae Gut symbionts Animals disperse seeds Resource-service Zoochory Pollination Phagophily/Defense g p y/ Zoochory (seed dispersal) Farming In rainforests 90%+ of trees are animal dispersed Ants do small seeds Tapirs do large seeds Service-service Facillitation Endosymbiosis Leave seeds in a pile of dung Some seeds require passage through gut to germinate 37 Human farming – Who benefits who? Mutualisms – the tour Resource-Resource Mycorrhizae Rhizobium Coral/Zooxanthellae Gut symbionts Resource-service 38 Pollination Phagophily/Defense g p y/ Zoochory (seed dispersal) Farming Service-service Facillitation Endosymbiosis 39 40 10 10/26/2009 Ants Coevolution in ants and aphids? Most insects that suck plant juices produce large quantities of nutritious excreta excreta. Ants are voracious generalists that are likely to attack any insect they encounter. The association of different genera of ants with different honeydew sources may simply reflect different sizes and levels of aggression, evolved in response to unrelated environmental factors factors. Ants may fail to attack aphids and leafhoppers because ants have evolved to protect other nectar sources, such as flowers and specialized nectaries. 41 Honeyguide 42 Mutualisms – the tour Resource-Resource Resource-service 43 Mycorrhizae Rhizobium Coral/Zooxanthellae Gut symbionts Pollination Phagophily/Defense Zoochory (seed dispersal) Farming Service-service Facillitation Endosymbiosis 44 11 10/26/2009 Clownfish-sea anenome Anenome is toxic Rare Why? Provides protection Clownfish evolved to not trigger Clownfish attacks butteflyfish B t… But Clownfish digests uneaten food, brings food in Ammonia (nitrogen) for anemone symbiotes 45 46 Mutualisms – the tour Resource-Resource Mycorrhizae Rhizobium Coral/Zooxanthellae Gut symbionts +/+ or +/0 Nurseplants Salt marsh Pollination Phagophily/Defense Zoochory (seed dispersal) Farming Service-service Facillitation Endosymbiosis Mutualism-comensalism Mutualism comensalism Resource-service Facilitation Shading prevents evapotranspiration prevents salinity Higher up salinity is not a problem Æcompetition Alpine 47 Wind protection Cold protection 48 12 10/26/2009 Conditional facilitation Mutualisms – the tour Often conditional Resource-Resource Competition in good conditions Facilitation in bad Resource-service 49 Your very cells depend on mutualisms Red vs. green vs. brown algae Pollination Phagophily/Defense Zoochory (seed dispersal) Farming Service-service Facillitation Endosymbiosis 50 Summary Some people think flagella & nucleus also symbiotic Chloroplasts happened repeatedly Mycorrhizae Rhizobium Coral/Zooxanthellae Gut symbionts Mutualisms are +/+ How can they evolve Most are based on reciprocity and enforcement against cheaters 3 categories Resource-Resurce Often plant gives sugar, gets minerals Gut symbionts Resource-service 51 Mycorrhizae, rhizobia, coral/zooxanthellae Services include defense/parasite cleaning, dispersal Pollination syndromes Service-service rare Facillitation – conditional mutualism Endosymbiosis 52 13 10/26/2009 Webs capture basic interactions Richness and webs Trophic cascades Dominant and keystone species Webs capture basic interactions Richness and webs Trophic cascades Dominant and keystone species 53 Food web is a map of who eats who 55 54 Real foodwebs are complex! 56 14 10/26/2009 More informative to show strength of interaction Fig. 17.5 57 58 More speciose webs add predators Webs capture basic interactions Richness and webs Trophic cascades Dominant and keystone species 59 60 15 10/26/2009 Ditto Webs capture basic interactions Richness and webs Trophic cascades Dominant and keystone species 61 62 Predator fish protect algae?! Trophic cascade 63 64 16 10/26/2009 Figure 21.17 Close to home 65 66 Dominant and keystone species Webs capture basic interactions Richness and webs Trophic cascades Dominant and keystone species 67 68 17 10/26/2009 Starfish are keystone species Periwinkles 69 70 Invasive ant changes plant community Fig. 17.9 71 72 18 10/26/2009 Top predators are likely to be involved in trophic cascades A mutualistic keystone species Saplings 400 300 200 100 0 73 Invasive top predator/ keystone species Lake Victoria I t d Introduced d Nil Nile Perch P h 1950s Displaced herbivorous tilapia Drove 65% of 500 cichlids extinct Small Medium Large 74 Overharvesting/exterminating top predators leads to trophic cascades 75 76 19 10/26/2009 Top predators link ecosystems together Summary Food webs show trophic links More rich communities typically 77 Add predators Longer Effects ripple down through webs Are often simplified due to great complexity I ffairly In i l linear li webs b gett an even/odd / dd tradeoff t d ff Keystone species have disproportionately large effect on structure of community Top predators are often keystone species 78 20
