zonation: paine to lubchenco

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  • 1

    III) Connell and the experimental revolution

    Consequences:

    1) Connells rule: upper limits set by physical processes, lower limits set

    by species interactions

    2) The dawn of appreciation and exploration of experimental field ecology

    Width of bar

    represents

    strength of

    importance

    III) Connell and the experimental revolution

    3) Importance of predation in determining zonation

    a) System / Pattern:

    Robert Paine 1966, 1974

    ii) Mytilus californianus (M) - California mussel

    - dominant in mid-intertidal

    - why not higher? Assumed desiccation

    - why not lower? Hmmm

    - lower limit remarkably stable

    - mussels can migrate, and settle below adult distribution

    - settlement may not be so important

    i) Rocky intertidal in Pacific Northwest (Olympic Peninsula)

  • 2

    III) Connell and the experimental revolution

    3) Importance of predation in determining zonation

    a) System / Pattern (contd):

    Robert Paine 1966, 1974

    iii) Pisaster ochraceus (P) - Ochre star

    - main predator on mussels

    - occurs mainly in lower intertidal

    - upper limit maybe set by desiccation?

    b) General hypothesis:

    i) Lower limit of Mytilus set by predation by Pisaster

    c) Specific hypothesis:

    i) In areas where Pisaster is removed, Mytilus

    distribution will expand lower

    mussels

    gooseneck barnacles

    acorn barnacles,

    tunicates, sponges,

    anemones

    pink corraline algae

    Rocky Intertidal Zonation

    Pisaster

  • 3

    d) Test:

    e) Results:

    i) Removed Pisaster from lower intertidal at two sites

    i) Over several years, Mytilus distribution extended

    down into lower intertidal zone

    ii) Replicate control area at each site with no

    removals

    ii) Issue with design:

    ii) Where Mytilus extended into lower intertidal zone,

    species diversity declined another story

    3) Importance of predation in determining zonation

    Robert Paine 1966, 1974

    without within-site

    replication of removal and control, how

    distinguish treatment and area effects????

    f) Conclusions:

    i) Predation sets lower limit of mussels

    ii) Supports general paradigm that biotic interactions

    set lower limits of distribution in intertidal

    3) Importance of predation in determining zonation

    Robert Paine 1966, 1974

  • 4

    g) Postscript:

    i) After experiment ended, Paine quit removing Pisaster, but

    contd to sample sites:

    3) Importance of predation in determining zonation

    time

    low

    high

    Lower limit

    of

    Mytilus

    Tatoosh site

    Mukkaw site

    a) At one site, lower limit moved back up as Pisaster reinvaded

    b) At other site, it did not!!!

    Robert Paine 1966, 1974

    removals

    c) Mussels larger at Mukaw by end of experiment

    g) Postscript:

    ii) Two important implications:

    3) Importance of predation in determining zonation

    a) Experimental design: site-site variability can mask experimental

    results --> more replication at the scale of sites

    b) Patterns: Distributions can be the result of temporary

    environmental conditions (in this case the reduction of

    Pisaster) referred to as History or Legacy Effects often

    resulting from episodic events

    - mussels move or recruit to lower intertidal, grow and escape

    predation by their greater size

    - Another example, southern California species that recruit to and

    remain in central California during episodic El Nios

  • 5

    III) Connell and the experimental revolution

    a) Upper limits determined by physical factors?

    Underwood and Jernakoff 1981, Oecologia

    4) Exceptions to the paradigm (of upper and lower limits)

    a) System: Grazing limpet and foliose macroalgae in intertidal

    of Australia.

    b) Pattern: Grazer occurs in zone above the alga that it feeds on.

    mid

    lower

    III) Connell and the experimental revolution

    Upper limits determined by physical factors?

    4) Exceptions to the paradigm (of upper and lower limits)

    c) General (alternative) hypotheses:

    - grazing determines upper limit of foliose algae

    - physical factors determine upper limit of algae

    - both grazing and physical factors

    - anything else - e.g., spores dont settle above upper limit of algae

    d) Specific hypotheses:

    - areas cleared and caged from grazers in mid-intertidal will become

    colonized by foliose algae

    - areas shaded will become colonized by foliose algae

    - areas both cleared of grazers and shaded will become colonized by

    algae

  • 6

    III) Connell and the experimental revolution

    Upper limits determined by physical factors?

    4) Exceptions to the paradigm (of upper and lower limits)

    e) Test:

    - full cage (with roof) provides shade and excludes grazers

    - roof only provides shade only

    - cage with no roof (fence) only excludes grazers

    - open is control grazers

    shade

    roof

    only

    fence open

    full

    cage

    III) Connell and the experimental revolution

    Upper limits determined by physical factors?

    4) Exceptions to the paradigm (of upper and lower limits)

    f) Results:

    - algae colonized the grazer exclusions (fences), but not the roof-only or

    the open plots ( grazers effects) any shade effects on abundance?

    - fences:

    - algal cover reached 100% but never lived long enough to reproduce

    - higher cover due to continuous recolonization by new spores

    - algae grew and survived to reproduce only in the (full cages - with roof)

    - algae never occurred in open plots

    grazers

    shade

    roof

    only

    fence open

    full

    cage no

    yes no

    yes no

    no no

    yes

    algae response algal reproduction

    interaction

  • 7

    III) Connell and the experimental revolution

    Upper limits determined by physical factors?

    4) Exceptions to the paradigm (of upper and lower limits)

    f) Conclusions:

    - upper limit not set by limited settlement

    - upper limit set by biotic interaction!!

    - upper limit of reproduction set by interaction between grazers and

    physical stress (physical factors effect grazer effect)

    grazers

    shade

    roof

    only

    fence open

    full

    cage no

    yes no

    yes no

    no no

    yes

    algae algal reproduction

    interaction

    III) Connell and the experimental revolution

    Lower limits determined by biological factors?

    4) Exceptions to the paradigm (of upper and lower limits)

    a) Intertidal organisms adapted to marine and terrestrial habitats

    b) Though most studies find that lower limit set by biotic

    interactions

    c) Exceptions:

    - Littorina (snail) limited to very high intertidal and will die if

    submerged too long

    - Two macroalgae, Selvitia and Fucus, die if submerged too long

    d) Few studies have tested this!!!!

  • 8

    IV) Horizontal patterns of distribution and abundance

    a) Background: Have focused on vertical zonation

    what about horizontal gradients?

    CHARACTERISTIC EXPOSED SHORE PROTECTED SHORE

    Dominated by Mussels (Mytilus) Fucoid algae

    Free Space Rare (

  • 9

    IV) Horizontal patterns of distribution and abundance

    f) Results: Exposed Shores

    At exposed sites - same pattern for both Fucus and predator removals (cages)

    and Fucus removals alone (open areas).

    a) barnacles colonize then are out-competed by mussels (no additional effect of

    predators: see open areas)

    b) If mussels are also removed then barnacles persist.

    Time

    Mussels

    Algae (Fucus)

    Control

    (no manipulation)

    Time

    Open

    (-Fucus)

    Mussels

    Barnacles

    Time

    Cage

    (-Fucus, -predators)

    Mussels

    Barnacles

    Cage

    (-Fucus,

    -predators,

    -mussels)

    Time

    Barnacles

    Time

    Mussels

    Barnacles

    Fucus

    Cage

    (-Predators,

    -grazers)

    - note pattern is similar to that in protected shores.

    IV) Horizontal patterns of distribution and abundance

    f) Results: Protected Shores

    Time

    Mussels

    Algae (Fucus)

    Control

    (no manipulation)

    At protected sites - differences between cages with Fucus and predator removals and

    Fucus removals (open areas).

    a) barnacles colonize and persist in low numbers outside of cages

    b) barnacles are out-competed in cages by mussels

    c) mussel abundance is kept low by predators

    d) barnacles persist in high number if you remove Fucus, mussels and predators.

    Predator (only) removals - If you remove only predators (including grazers) algae and

    barnacles colonize but get out-competed by mussels.

    Time

    Barnacles

    Open

    (-Fucus)

    Mussels

    `

    Cage

    (-Fucus,

    -predators,

    -mussels)

    Time

    Barnacles

    Time

    Mussels

    Barnacles

    Fucus

    Cage

    (-Predators,

    -grazers)

    Time

    Cage