Community Structure:

Top-Down vs. Bottom-Up Control

Hairston, Smith and Slobodkin (1960)

Community Dynamics

Carnivores

Herbivores Plants

Detritivores

Frees plants

from herbivore control

Resource limited

control

Hairston Slobodkin

Other inferences of Hairston et al, 1960

1) Exceptions not important

2) All communities have 3 trophic levels

3) Omnivory not important

4) External abiotic factors - not controllers

??

X

X

X

Critiques

Too Simple

1) Species differences matter

2) Plant dominance could be explained by good defences

Menge, 2000. J.exp.Mar.Biol.Ecol

Early example of top-down control

P. Dayton

All predators present

Predators excluded

Menge and Sutherland, 1976

Predation is weak

High wave energy - effects of predation -weak

Moderate wave energy - effects of predation - strong

Effects of predation by whelks.

Menge Sutherland

Top-down forces along environmental gradients

Bottom Up Control

Fretwell, 1977, 1987

- availability of plant material governs structure of food chains

- Low productivity - 1 link (plants)

- Higher productivity - add links

Bottom up control

Gardner 2013. Mar. Ecol Progr. Ser.

Wellington HarbourCook Strait

Mytilus galloprovinciales

Bottom up control

Gardner 2013. Mar. Ecol Progr. Ser.

Cook Strait

Lab

Intertidal

Looked at

1)Mortality

2) Growth rate

3) Gonad condition

Bottom up control

Gardner 2013. Mar. Ecol Progr. Ser.

Cumulative Mortality

Oct Nov Dec Jan Feb Mar Apr May

30

20

10

0

Cook Strait

Lab

Intertidal

Bottom up control

Gardner 2013. Mar. Ecol Progr. Ser.

.05

.04

.03

.02

.01

GrowthRate(mm/day)

Cook Strait

Lab

Intertidal

Bottom up control

Gardner 2013. Mar. Ecol Progr. Ser.

Oct Nov Dec Jan Feb Mar Apr May

Cook Strait

Lab

IntertidalGonad

condition

Top-down vs Bottom-up in tide pools

Boiler Bay, Oregon

Nielsen, K. 2001. Ecological Monographs 71: 187

Karina Nielsen

Top-down vs Bottom-up in tide pools

Artificial Tide Pools

Top-down vs Bottom-up in tide pools

Nielsen, K. 2001. Ecological Monographs 71: 187

Karina Nielsen

Top-down vs Bottom-up in tide poolsTop-down vs Bottom-up in tide pools

Nielsen, K. 2001. Ecological Monographs 71: 187

Karina Nielsen

Top-down vs Bottom-up in tide pools

Predictions

Top-down vs Bottom-up in tide pools

Nielsen, K. 2001. Ecological Monographs 71: 187

Karina Nielsen

Top-down vs Bottom-up in tide poolsTop-down vs Bottom-up in tide pools

Nielsen, K. 2001. Ecological Monographs 71: 187

Karina Nielsen

Top-down vs Bottom-up in tide pools

Nielsen, K. 2001. Ecological Monographs 71: 187

Karina Nielsen

Top-down vs Bottom-up in tide pools

Nielsen, K. 2001. Ecological Monographs 71: 187

Karina Nielsen

Orca

Sea Otter

Kelp

Urchins

Ecological Relationships in Kelp Forests

Transplant mussels and barnacles (filter feeders) to urchin-dominated andkelp-dominated substrates

Transplant mussels and barnacles (filter feeders) to urchin-dominated andkelp-dominated substrates

Expected (top down)

Urchin - dominated

Kelp - dominated

Transplant mussels and barnacles (filter feeders) to urchin-dominated andkelp-dominated substrates

Expected (top down) Observed (bottom up)

Urchin - dominated

Kelp - dominated

Kelp - dominated

Urchin - dominated

Clearly - can be a complex interaction

Increased nutrient

Increased algae

Increased benthic filter feeders

Increased consumers (predation)

control

Interaction of Systems

Leonard, Levine, Schmidt & Bertness. 1998. Flow-driven variation in intertidal community structure in a Maine estuary. Ecology 79:1395-1411

G.H. Leonard Schmidt Levine Bertness

Damariscotta River

Interaction of Systems

Leonard et al, 1998

Low flow

High flow

Interaction of Systems

• increased seaweed growth

• increased filter feeder growth

• increased larval settlement

• low consumer efficiency

• higher densities of organisms with planktonic larvae• more spatial competition

• increased consumer pressure

• increased sedimentation

• increased consumer mortality

• lower densities of organisms with planktonic larvae

• less spatial competition

Leonard et al, 1998

Hydrodynamics

Time

Flow rate

Leonard et al, 1998

Community structure

barnacles

mussels Bare space

Fucus

High flow Low flow

Percent cover Percent cover

Tide

height

Leonard et al, 1998

Recruitment rates

Density(#/100 cm2)

High flow

Low flow

Barnacles Mussels Snails

Leonard et al, 1998

Crab predation

Predation Intensity(% mortality)

High flow

Low flow

On Littorina, Nucella, Mytilus

Leonard et al, 1998

diatoms

grazers

crabs

mussels barnacles

Nutrients Larvae Plankton

Leonard et al, 1998

diatoms

grazers

crabs

mussels barnacles

Nutrients Nutrients Larvae LarvaePlankton Plankton

diatoms

grazers

crabs

mussels barnacles

whelks

High flowLow flow

Plants

Consumers

Predators

Interference competition, exploitative competition for resources other than food

(-) Depletion of more nutritious, palatable or accessible prey

(-)

Induced morphological or chemical defenses, hiding, retreat to refuges

(-)

Stimulation of area-specific primary productivity

(+)

Powers. ‘92. Ecology 73: 733

Cover from (for) predators

- (+)

+ (-)