Schmitt, R'J' 1987' Indirect interactions between prey: apparent predation, predator aggregation, an

1
Examples of Indirect Effects and HOIs
Schmitt, R.J. 1987. Indirect interactions
between prey apparent predation, predator
aggregation, and habitat segregation. Ecology
681887-1897. Wootton, J.T. 1994. Predicting
direct and indirect effects an integrated
approach using experiments and path analysis.
Ecology 75151-165. Schmitt, R.J., C.W. Osenberg
and M.G. Bercovitch. 1983. Mechanisms and
consequences of shell fouling in the kelp snail,
Norrisia norrisi (Sowerby) (Trochidae) indirect
effects of octopus drilling. J. Exp. Mar. Biol.
Ecol. 69267-281.
2
Schmitt, R.J. 1987. Indirect interactions
between prey apparent predation, predator
aggregation, and habitat segregation. Ecology
681887-1897.
3
The Natural Pattern
4
High Relief Reefs
5
Predators
- Apparent Competition -
Snails
Bivalves
Suspended particulates
Benthic micro-algae
6
Mortality of outplanted Chama on Cobble Reefs
7
Density of gastropods before and after addition
of bivalves (Chama).
8
Density of predators following addition of
bivalves (Chama)
9
Number of dead gastropod shells following
addition of bivalves (Chama)
10
Proportion of marked snails found dead
11
Predators
- Apparent Competition -
Snails
Bivalves
Suspended particulates
Benthic micro-algae
12
Wootton, J.T. 1994. Predicting direct and
indirect effects an integrated approach using
experiments and path analysis. Ecology
75151-165.
13
Intertidal food web

Birds
-
Starfish

-
-


Snail
-

-

-

-

-
-
-
Goose Barn.
Acorn Barn.
Mussels
-
-
-
14
Response to Bird Exclusion
Birds
Starfish
(no data)
Snail
Goose Barn.
Acorn Barn.
Mussels
15
Intertidal food web

Birds
-
Starfish

-
-


Snail
-

-

-

-

-
-
-
Goose Barn.
Acorn Barn.
Mussels
-
-
-
16
Hypothesis 1

Birds
-
Starfish

-
-


Snail
-

-

-

-

-
-
-
Goose Barn.
Acorn Barn.
Mussels
-
-
-
17
Hypothesis 1

Birds
-
Starfish

-
-


Snail
-

-

-

-

-
-
-
Goose Barn.
Acorn Barn.
Mussels
-
-
-
18
Hypothesis 2

Birds
-
Starfish

-
-


Snail
-

-

-

-

-
-
-
Goose Barn.
Acorn Barn.
Mussels
-
-
-
19
Hypothesis 3

Birds
-
Starfish

-
-


Snail
-

-

-

-

-
-
-
Goose Barn.
Acorn Barn.
Mussels
-
-
-
20
Hypothesis 3
Hypothesis 1
Hypothesis 2
Birds
Birds
Birds
Starfish
Starfish
Goose Barn.
Snail
Acorn Barn.
Mussels

Acorn Barn.
Snail
Goose Barn.
Goose Barn.

Acorn Barn.
Snail
Mussels
Mussels
21
Hypothesis 3
Hypothesis 1
Hypothesis 2
Birds
Birds
Birds
Starfish
Starfish
Goose Barn.
Snail
Acorn Barn.
Mussels

Acorn Barn.
Snail
Goose Barn.
Goose Barn.

Acorn Barn.
Snail
Mussels
Mussels
22

• Response to Snails (Nucella)
• Weak effects of snails
• Bird effects do not depend on /- of snails
• Supports Hypothesis 1

23
Hypothesis 3
Hypothesis 1
Hypothesis 2
Birds
Birds
Birds
Starfish
Starfish
Goose Barn.
Snail
Acorn Barn.
Mussels

Acorn Barn.
Snail
Goose Barn.
Goose Barn.

Acorn Barn.
Snail
Mussels
Mussels
24

• Response to Gooseneck Barnacles (Pollicipes) and
  Birds
• Pollicipes reduced snails, acorn barn., and
  mussels.
• Birds had no effect on starfish.
• In the absence of Pollicipes, birds had no
  effect on snails, acorn barnacles, or mussels.
  (key result)
• Inconsistent with Hypotheses 2 and 3.

25
Hypothesis 3
Hypothesis 1
Hypothesis 2
Birds
Birds
Birds
Starfish
Starfish
Goose Barn.
Snail
Acorn Barn.
Mussels

Acorn Barn.
Snail
Goose Barn.
Goose Barn.

Acorn Barn.
Snail
Mussels
Mussels
26
Schmitt, R.J., C.W. Osenberg and M.G. Bercovitch.
1983. Mechanisms and consequences of shell
fouling in the kelp snail, Norrisia norrisi
(Sowerby) (Trochidae) indirect effects of
octopus drilling. J. Exp. Mar. Biol. Ecol.
69267-281. its actually an example of
higher order interactions
27
Norrisia norrisi
2 octopus drill holes (one with barnacles removed
28
A kelp forest in southern California
29
Microhabitat Distribution of Norrisia norrisi
dislodgement rate 4 per day
30
Mortality rate of tethered Norrisia norrisi
31
Relationship between fouling and drill holes
32
Drill holes and barnacle settlement
33
Can live snails prevent barnacle settlement?
Percent with barnacle settlement
Answer No (but drill holes do matter).
34
Effect of fouling on return to refuge
35
Effect of fouling on escape velocity (cm/s) from
Pisaster
No. (but drill holes do matter)
36
Higher Order Interaction the effect of lobster
on snails depends on the abundances of octopus
and barnacles