lecture 20 competition and predation 1) review: intertidal zonation 2) causes of zonation -physical...

Download Lecture 20 Competition and Predation 1) Review: intertidal zonation 2) Causes of zonation -Physical and biological factors -Temperature and desiccation

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  • Slide 1
  • Lecture 20 Competition and Predation 1) Review: intertidal zonation 2) Causes of zonation -Physical and biological factors -Temperature and desiccation (Foster) -Competition and predation (Connell) 3) Competition on sediment shores -Deposit feeders (Levinton, Posey) 4) Keystone species -Pisaster
  • Slide 2
  • Intertidal Zonation: -Subclassifcation of ecosystems -Smaller zones with unique physical characteristics -Unique habitat that favors particular species
  • Slide 3
  • Slide 4
  • Olympic Peninsula, Washington State
  • Slide 5
  • Newport Beach, CA
  • Slide 6
  • Kodiak Island, AK
  • Slide 7
  • Rio De Janeiro, Brazil
  • Slide 8
  • Atlantic Coast North America Large kelps (Laminaria) Red algae Small kelps, mussels Barnacles, predatory snails Microalgae and grazers: herbivorous snails
  • Slide 9
  • Large kelps, Small kelps, mussels Barnacles, predatory snails Microalgae and grazers: herbivorous snails Pacific Coast North America Red algae
  • Slide 10
  • Slide 11
  • Causes of Zonation
  • Slide 12
  • water Frank 1965 Observation High shore organisms: exoskeletons Hypothesis Desiccation sets upper tidal limits Prediction Dripping water will cause increase in upper tidal limits
  • Slide 13
  • Chthamalus stellatus Balanus balanoides Balanus crenatus high-shore intertidal mid-shore intertidal subtidal Foster, 1960-70s
  • Slide 14
  • Temperature At 100% humidity: Mean lethal time (hours) lethal temperature (C) high-shore species (Chthamalus) mid-shore species (Balanus balanoides) subtidal species (Balanus crenatus)
  • Slide 15
  • Desiccation Chthamalus (high-shore) S. balanoides (mid-shore) B. crenatus (subtidal) At 17-20C, 0% humidity:
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  • Slide 17
  • heat an desiccation stress
  • Slide 18
  • Balanus balanoides low shore Chthamalus stellatus high shore Species Interactions: Competition
  • Slide 19
  • Biological factors: Larval settlement Larvae tend to settle on tidal heights based on environmental cues Barnacles: Gregarious settlement Barnacle cyprid larva
  • Slide 20
  • Slide 21
  • Connell (1961) Chthamalus Balanus Upper limits of Both set by physical stress What sets the lower limits of Chthamalus?
  • Slide 22
  • Bottom of Chthamalus zone Top of Chthamalus zone Experimental removal of Balanus
  • Slide 23
  • Balanus grows 70% > than Chthamalus Balanus overgrows and undercuts Chthamalus Connells Observations:
  • Slide 24
  • What sets the lower limits for Balanus?
  • Slide 25
  • Predation Connell (1960s) Predatory Snails - Nucella
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  • Slide 27
  • Low intertidal: transplanted Balanus below their natural lower limit Predation: caging experiments Connell (1961)
  • Slide 28
  • Temperature and desiccation prevent both Chthamalus and Balanus from living at higher levels Competition from Balanus prevents Chthamalus from inhabiting the middle zone Predation by snails sets the lower limits of the distribution of Balanus Balanus zone Chthamalus zone
  • Slide 29
  • Paradigm of Intertidal Zonation:
  • Slide 30
  • Sediment vs Rocky Shores High heat and desiccation stress Stable substrate Sedentary lifestyles Resident predators Benthic macroalgae, microalgae Rocky Shores Less heat and desicc stress Unstable substrate No SSOs Transient and mobile predators Microalgae, drift macroalgae Sediment Shores
  • Slide 31
  • Predator Exclusions on Dissipative Shores large predators excluded control
  • Slide 32
  • Hargrave (1970) Trophic Structure of Mudflats Deposit feeders Heterotrophic bacteria POM Benthic Algae
  • Slide 33
  • Competition for Food on Sediment Shores Jeff Levinton (1972) American Naturalist Suspension Feeders: Deposit Feeders:
  • Slide 34
  • Slide 35
  • Growth (mm)

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