Transcript T. confusum
How do species interact with one another to make stable Ecological Communities? Ecological Effects of Species 1 on Species 2: (A) Effect is Positive (+) if species 1 increases the numbers of species 2. (B) Effect is Negative (-) if species 1 decreases the numbers of species 2. Species 2 +/- Ecological Effects of One species on the other + - + Mutualism Predation - Predation Competition Species 1 Species 2 Ecological Effects of One species on the other + - + Mutualism Predation - Predation Competition Species 1 Mutualism is an interaction between two (or more) species that is beneficial (+) to both (all) species. Mutualism is an interaction between two (or more) species that is beneficial (+) to both (all) species. Algae: + effects on fungi: algal photosynthesis produces sugars and oxygen for the fungus. Fungus: + effects on algae: fungus absorbs nutrients from the atmosphere and produces CO2 which permits the alga to photosynthesize. Fungus also protects the alga from drying out. Mutualism is an interaction between two (or more) species that is beneficial (+) to both (all) species. Beetles: + effects on fungi: the beetle ‘plants’ the fungal spores and maintains optimal humidity for fungal growth. Fungus: + effects on beetle: fungus provides nutrition for the beetle. Ant-Aphid mutualism Ants: protect the aphid from predators. Aphids: provide plant sugars for the ants Species 2 Ecological Effects of One species on the other + - + Mutualism Predation - Predation Competition Species 1 Competition occurs when of two species each require the same limited resource. The availability of the resource to one species is negatively influenced by the presence of the other species. It is a "-/-" interaction. Gause’s Competitive Exclusion Principle: When two species make similar demands on a limited resource, then one or the other species will go extinct as a result of competition for the resource. Paramecium caudatum Paramecium aurelia Gause’s Experiments Single Species Populations: each survives indefinitely when reared alone. Competition Populations: P. aurelia out-competes P. Caudatum when reared Together. Competition occurs when of two species each require the same limited resource. The availability of the resource to one species is negatively influenced by the presence of the other species. It is a "-/-" interaction. Tribolium confusum Thomas Park’s experiments Tribolium castaneum Single Species Equilibrium Population Sizes when reared ALONE Climate T. castaneum T. confusum Cold-Dry 21 208 Cold-Wet 99 225 Warm-Dry 150 237 Warm-Wet 401 264 Hot-Dry 77 190 Hot-Wet 306 329 Predict the Winner in Competition Single Species Equilibrium Population Sizes when reared ALONE Climate T. castaneum T. confusum Predicted Winner in Competition Cold-Dry 21 208 confusum Cold-Wet 99 225 confusum Warm-Dry 150 237 confusum Warm-Wet 401 264 castaneum Hot-Dry 77 190 confusum Hot-Wet 306 329 ?Toss Up Observed Competitive Outcomes: Percent Wins when raised together Climate T. castaneum T. confusum Predicted Winner in Competition Cold-Dry 0% 100% confusum Cold-Wet 30% 70% confusum Warm-Dry 13% 87% confusum Warm-Wet 86% 14% castaneum Hot-Dry 10% 90% confusum Hot-Wet 100% 0% Toss Up Unusual Outcomes based on Single Species Predictions Observed Competitive Outcomes: Percent Wins Climate T. castaneum T. confusum Predicted Winner in Competition Cold-Dry 0% 100% confusum Cold-Wet 30% 70% confusum Warm-Dry 13% 87% confusum Warm-Wet 86% 14% castaneum Hot-Dry 10% 90% confusum Hot-Wet 100% 0% Toss Up Gause’s Competitive Exclusion Principle: When two species make similar demands on a limited resource, then one or the other species will go extinct as a result of competition for the resource. With T. castaneum and T. confusum, One species won and the other went extinct in every one of the 170 competition populations Where they were raised together. Changing the Climate from Hot-Wet to Cold-Dry Changed the identity of the winning species from T. castaneum to T. confusum. Stochastic Outcome: In Intermediate Climates each species won in at least some of the competition populations. The outcome of competition was not completely Predictable. Changing the Hot-Wet Environment by ADDING a thrid species, the pathogen, Adelina tribolii Changed the identity of the winning species from 100% T. castaneum to 80% T. confusum. Predator-Prey Arms Races: Reciprocal Co-Evolution of Offense and Defense Evolution of Garter Snake (Predator) Exploitation Newt (Prey) Evolution of Newt (Prey) Defense against Garter Snake (Predator) predation Species 2 Ecological Effects of One species on the other + - + Mutualism Predation - Predation Competition Species 1 Arms-Race Co-evolution Selection by Predator on Prey Exploitative Ability of Predator Selection by Prey on Predator Defensive Ability of Prey Life-Dinner Principle Predator is hunting for its dinner. If it fails in an encounter with a prey, it loses only a meal and the effect on predator fitness is relatively small. Prey is running for its life. If it fails in an encounter with a predator, it loses its life and the effect on prey fitness is very large. Natural Selection on the Prey species to evolve defenses is STRONGER than Natural Selection on the Predator Species to evolve hunting ability. Arms-Race Co-evolution is Typically Asymmetrical Selection by Predator on Prey is Strong Exploitative Ability of Predator Selection by Prey on Predator is Weak Defensive Ability of Prey Intensity of Coevolution depends upon the Reciprocity of the fitness effects of Predator on Prey and Prey on Predator. Life-Dinner Principle suggests a lack of reciprocity of fitness effects, and thus the intensity of coevolution resulting from the arms race is weak. However, when Prey are Dangerous or Toxic, then Dinner for the Predator means a risk of Death. This Reciprocity of the fitness effects means a STRONG Arms Race Tetrodotoxin in skin of Newt. Na+ channel blocker, causes paralysis. Toxic to most animals. Found in crabs, fugu fishes, annelid worms and algae. Possibly produced by symbiotic bacteria Species of Newt Skin Toxicity in “Mouse Units” Taricha granulosa Taricha torosa Taricha rivularis Notophthalmus viridescens 25,000 1,000 –2,500 1,000 –2,500 20 Range of Taricha (prey) species T. granulosa T. granulosa, T. torosa, T. rivularis T. granulosa, T. torosa T. torosa Range of Thamnophis sirtalis Benton Study Sites Tenmile Bioassay of Predator Resistance to Tetrodotoxin 1. Measure baseline speed 2. Inject known dose of TTX. 3. Measure post-injection speed. 4. “TTX resistance” is the % reduction in speed after injection of toxin. Nonresistant T. sirtalis Predator Resistance (% reduction) Resistant T. sirtalis 100 Coluber ‘”Super” Resistant T. sirtalis 50 0 0.01 0.1 1 10 100 1000 Prey Toxin [mouse units of TTX] 10000 Geographic Variation in Newt Toxicity Geographic Variation in Snake Resistance NonResistant T. granulosa Weakly Resistant Strongly Resistant T. granulosa, T. torosa, T. rivularis T. granulosa, T. torosa T. torosa Super Resistant