TRITROPHIC INTERACTIONSSlide 2A TRITROPHIC INTERACTIONANOTHER TRITROPHIC INTERACTION (I)TRITROPHIC INTERACTION (II)FOOD CHAIN (I)FOOD CHAIN (II)PREDICTED DYNAMICS OF TRITROPHIC INTERACTIONS (I)PREDICTED DYNAMICS OF TRITROPHIC INTERACTIONS (II)WILLOW-HARE-LYNXWOLF-MOOSE INTERACTION REVISITED (I)WOLF-MOOSE INTERACTION REVISITED (II)Moose-Balsam Fir InteractionBalsam Fir-Moose-Wolf Interaction on Isle Royale (I)Balsam Fir-Moose-Wolf Interaction on Isle Royale (II)Balsam Fir-Moose-Wolf Interaction on Isle Royale (III)Balsam Fir-Moose-Wolf Interaction on Isle Royale (IV)EXPERIMENTAL STUDIES OF TRITROPHIC INTERACTIONSEffects of Predation by Birds on Herbivory by Forest Insects (I)Slide 20Effects of Predation by Birds on Herbivory by Forest Insects (IIa)Effects of Predation by Birds on Herbivory by Forest Insects (IIb)Effects of Predation by Birds on Herbivory by Forest Insects (III)Influence of Predation on Competition in an Amphibian Community (1)Influence of Predation on Competition in an Amphibian Community (2)Effect of Predation on Competition (3a)Effect of Predation on Competition (3b)Effect of Predation on Competition (3c)Effect of Predation on Competition (4)AN EXPERIMENT THAT DEFINED KEYSTONE PREDTOROTHER STUDIES OF KEYSTONE PREDATORSOf Acorns, Mice, Moths, Deer, Ticks, Spirochetes -and Lyme Disease?(1)Of Acorns, Mice, Moths, Deer, Ticks, Spirochetes -and Lyme Disease? (2)Of Acorns, Mice, Moths, Deer, Ticks, Spirochetes -and Lyme Disease? (3)Of Acorns, Mice, Moths, Deer, Ticks, Spirochetes -and Lyme Disease? (4)Of Acorns, Mice, Moths, Deer, Ticks, Spirochetes -and Lyme Disease? (5)Of Acorns, Mice, Moths, Deer, Ticks, Spirochetes -and Lyme Disease? (6)Of Acorns, Mice, Moths, Deer, Ticks, Spirochetes -and Lyme Disease? (7)Of Acorns, Mice, Moths, Deer, Ticks, Spirochetes -and Lyme Disease? (8)Risk of Lyme DiseaseSlide 41TRITROPHIC INTERACTIONS READINGS: FREEMAN, 2005 Chapter 53TRITROPHIC INTERACTIONS•Eating (trophic) relationships often link several species in a community through herbivory, predation and/or parasitism.•When the links go across three eating (trophic) levels, they are called tritrophic interactions. •Species that play an special role in trophic relations are called “keystone species”.A TRITROPHIC INTERACTION •Hover flies sip nectar from flowers and in turn are eaten by a spiders.•This is a version of: Predators eat herbivores, and herbivores eat plants.ANOTHER TRITROPHIC INTERACTION (I)•Daphnia are herbivores on a unicellular algae and the prey of damsel flies.•A decrease in algae would soon result in a decrease in Daphnia and later a decrease in damsel flies.TRITROPHIC INTERACTION (II)•A sudden decrease in Daphnia would result in a decrease in damsel fly larvae and an increase in unicellular algae.•A sudden increase in damsel fly larvae would result in a(n) _____ of Daphnia and a(n) _____ of unicellular algae.FOOD CHAIN (I)•A trophic interaction that links three or more levels is called a food chain.•Where the trophic levels are dynamically linked, any change in abundance of one population within the chain can result in changes in abundance of the other populations.FOOD CHAIN (II)•All food chains begin with producers [green plants, green algae and blue-green algae (cyanobacteria)].•Herbivores are known as primary consumers.•Predators are known as secondary or higher level consumers.PREDICTED DYNAMICS OF TRITROPHIC INTERACTIONS (I)•Where eating relations exert control on the abundance of populations within a food chain, a change in the abundance of one population can have an influence on the other populations.•A change in abundance of producers will first change the abundance of primary consumers and later the abundance of secondary consumers.PREDICTED DYNAMICS OF TRITROPHIC INTERACTIONS (II)•A change in abundance of secondary consumers will first change the abundance of primary consumers and later the abundance of producers.•A change in abundance of primary consumers will change the abundance of one or both of the other immediate trophic levels and the timing of change is difficult to predict (depends on life history characteristics, etc.).WILLOW-HARE-LYNX•Willow is a primary food of artic hare in the winter when food is scarce.•Although evidence suggests that lynx control hare cycles, the hare population is subject to both top down and bottom up control.•The interaction of food and predation has a strong influence on hare abundance.WOLF-MOOSE INTERACTION REVISITED (I)•There is no strong evidence that wolves control moose populations on Isle Royal.•There is good evidence that declining moose populations may result in wolf population increases.WOLF-MOOSE INTERACTION REVISITED (II)•Moose populations are known to fluctuate dramatically -- from a low of around 500 to a high of around 2,500 in the last nearly 50 years.•Prior to the immigration of wolves, the moose population showed similar fluctuations. •What is a primary cause of these fluctuations??Moose-Balsam Fir Interaction•The island had a high density of balsam fir (a common Christmas tree), estimated at 46% of overstory prior to moose immigration. Today, it is only 5%.•Nearby islands, which have no moose, have balsam fir as a large component of their forests.•Thus, the decline of balsam fir has been attributed to moose browsing.•Although not optimum forage, it can be up to 59% of food for moose during the winter.Balsam Fir-Moose-Wolf Interaction on Isle Royale (I)•Current research is focused on the tritrophic interaction between wolf-moose-balsam fir.•It attempts to use tree ring data to account for fluctuations in moose and wolf populations.Balsam Fir-Moose-Wolf Interaction on Isle Royale (II)•This research is being conducted using a bottom up and top down (trophic cascade) model.•It also uses data on temperature and precipitation in the form of annual actual evapotranspiration (AET).Balsam Fir-Moose-Wolf Interaction on Isle Royale (III)•The bottom up hypothesis predicts that plant growth is determined by temperature and precipitation. This is a version of the primary production scenario.•The top down hypothesis predicts that changes in one trophic level result in opposite changes in the level below it. •For example, a decrease in moose abundance should produce increased plant growth if moose herbivory limits plant growth.Balsam Fir-Moose-Wolf Interaction on Isle Royale (IV)•Future observations on Isle