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KEYSTONE
PREDATOR
Pacific Northwest
http://www.youtube.com/watch?v=P8FlmTlmdzc
Location of Robert Paine’s 25year investigation on how the
loss of a top predator affects
the rest of the intertidal
community.
WHAT IS A
COMMUNITY?
a group of populations of
different species living
close enough together to
interact
WHAT DETERMINES STRUCTURE
OF AN ECOLOGICAL COMMUNITY?
•! Is it just environmental factors or do the species
themselves have a role to play?
•! If they do, are all species equal or are some
more important than others?
INTERTIDAL SPECIES
•! Producers – produce their own food
•! Consumers – rely on other species for food
•! stationary filter-feeders
•! mobile predators
PRODUCERS:
ALL RED ALGAE
(RHODOPHYTA)
•!Nori Seaweed - Porphyra
•!Black Pine - Neorhodomela
•!Coral Weed - Corallina
Black Pine: Neorhodomela
Nori: Porphyra
Coral Weed - Corallina
CONSUMERS:
FILTER-FEEDERS
•!Acorn Barnacle - Balanus
•!Goose Neck Barnacle - Mitella
•!Mussel - Mytilus
Acorn Barnacle: Balanus
Mussel: Mytilus
Goose Neck Barnacle: Mitella
CONSUMERS:
PREDATORS
•! Whelk - Nucella
•! Chiton - Katharina
•! Starfish - Pisaster
Whelk: Nucella
Chiton: Katharina
Sea Star: Pisaster
Exercise One:
Flexing Your Mussels
•! Goal: Determine dominance hierarchy among three
sessile consumers
•! How do species interact with each other?
•! Which species are competitively dominant over others?
•! Paint a patch of one stationary competitor (e.g., Acorn
Barnacle) over about third to half of the intertidal area
•! Observe at least 10 weeks
•! Did either of the other two stationary competitors
displace Acorn Barnacle?
Note: Do not count empty squares that get occupied by other species.
Competitive Dominance Hierarchy
•!Applies to stationary species – producers and
sessile consumers
•!Looks at a species’ ability to out-compete and
ultimately displace other species
•!In constructing dominance hierarchy diagram,
arrows point to stronger competitors
•!E.g., black pine starts growing on and ultimately
takes over all space occupied by Nori seaweed
•!Black pine is competitively dominant over Nori
seaweed
•!Represented in diagram as:
Nori seaweed
Black pine
Competitive Dominance Hierarchy
Exercise Two:
You Are What You Eat
•! Examine gut contents of 10 consumer predators
and record information in table
•! Run simulation for 100 weeks
•! Click on microscope and examine gut contents of
10 predators
•! Determine percentages of each species
consumed by each predator
•! Construct food web diagram
FOOD WEB DIAGRAM
•! Summarizes information about interconnected
sets of food chains in the same ecosystem
•! Uses arrows to connect species to various
species that they eat
•! Like in a dominance hierarchy diagram, the
arrows point from species consumed to
species that consumes them
•! Usually predators at top, herbivores in
middle, and producers at bottom
Note: Do not count organisms with empty guts.
Food Web Diagram
Do not
include
information
from
dominance
hierarchy.
EXERCISE Three:
Who Rules The Rock?
•!Determine which predator’s removal has the biggest
impact on the intertidal community
•!Before starting: Make prediction about the impact of
removing each predator from the community.
•! Exercise:
•! Record starting population size of each species
•! Remove one of the consumer predators
•! Run simulation by clicking Step 200 button
•! Record new population sizes
•! Repeat for the other predators; be sure to reset for each
trial
Abundance Data – Removal Experiment
SPECIES
BEFORE REMOVALS
AFTER WHELK REMOVAL
AFTER CHITON REMOVAL
AFTER STARFISH REMOVAL
Nori
Green Algae
Coral Weed
Mussel
Acorn Barnacle
Goose Neck Barnacle
Whelk
Chiton
Starfish
0
0
0
Who Rules the Rock?
•! Not all species in ecosystem are equal
•! Which one is the dominant species?
•! Dominant species - the ones that comprise
the greatest biomass or highest abundance
•! Which one is keystone species?
•! Keystone species - the one which, when
removed, causes the community structure
to change dramatically
http://www.youtube.com/watch?v=Ng6CNn6XnBg
Starfish – Keystone Species
Starfish
•! the keystone
species
•! governs biological
diversity in the entire
intertidal zone
Tatoosh Island, Washington:
What Happened When the
Keystone Species Was Removed?
Mussel bed kept in check by Pisaster
When Pisaster was regularly removed the mussel bed migrated one meter
further down the intertidal zone. Yellow line indicates boundary of mussel
bed before Pisater was removed.
Salmon, Keystone Species in
Pacific Northwest
Salmon are dying in
record numbers
because of:
•! Harvesting
•! Hatcheries
•! Habitat changes
•! Hydropower
Salmon support
wildlife from birds
to bears to orcas
Without keystone
species what will
happen to the rest
of the ecological http://www.youtube.com/watch?v=hgXHvxon3_g
community?
http://www.wdfw.wa.gov/hab/salmonwild/salmonwild2.pdf
Species Reintroduction
Take the on-line quiz before beginning this part.
+ Species Reintroduction
+ Invasion – Carcinus meanus
+ Biocontrol – Sacculina carcini
Important Dates
11/17, Wednesday:
+ Stream ecology lab report
+ Notebooks
11/19, Friday:
+ Pick up notebooks – 1PM-4PM
Walker6213 (if graded)
11/22, Tuesday – last date to submit all
outstanding assignments
Power point presentations will be posted in a
folder on RPI-LMS before Thanksgiving
11/30, Tuesday @ 9AM - LAB EXAM