Transcript Community Interactions - Diablo Valley College

Community Interactions
Chapter 53
Community Ecology
• Community – all the species in a given
location at a given time
• Habitat the physical environment they live
in, e.g. Redwood forest
• Niche – how a species uses the resources
in its habitat
– Builds nest in tree top vs. lower branches
• Similar species coexist by Niche
specialization.
Fig. 32.8a
Fig. 32.8b
Energy Transfer in
Ecosystems Food / Energy
Pyramid
Primary Consumers eat producers,
incorporating the energy into the next
level.
• Only 10 % of energy consumed moves to
next level
– Animals loose 90% of the energy at each level
– Why are Big Fierce Animals so Rare??
• Consumers are Heterotrophs
Simple
Food Chains
Trophic Levels
Both
Marine and
Terrestrial
Food Webs
• Energy transfer follows trophic levels
• Many animals eat at several trophic
levels
• Omnivores: like most of us
– At salad bar you’re a herbivore
– Eating a burger makes you a carnivore
marsh hawk
Higher
Trophic
Levels
Sampling of connections in a
Tall grass prairie food web
crow
upland
sandpiper
garter snake
frog
weasel
spider
Second
Trophic
Level
sparrow
earthworms, insects
First
Trophic
Level
badger coyote
prairie vole
grasses, composites
pocket gopher
ground squirrel
Plant Community structure
• Individualistic view
(Gleason)
• Interactive view (Clements)
• Whittaker’s test
• Plant communities are loose
associations without
discrete boundaries
Competitive Exclusion
• The more similar two species’ niches
the more they compete.
• No two species can share the exact
same niche- one dies out.
• Species evolve to diverge their
niches by Resource Partitioning
Paramecium caudatum
Paramecium aurelia
Competitive exclusion
Fig. 32.10
Follow up:
• Gause next added Paramecium
aurelia with P. bursaria
• They used the resources differently
and both survived at lower levels.
• Resource partitioning species evolve
to avoid competition. – why?
Fig. 32.11
Resource Partitioning
Competition for space on the rocks
Weak competitors stuck higher up in the intertidal
Bristly
foxtail
Indian
mallow
Smartweed
• Nuthatch crawls down the
tree’s bark eating insects
• Brown Creeper crawls up
the same trees eating
insects
Caulerpa taxifolia suffocating
a marine ecosystem
• Introduced
species often out
compete natives
• Lack predators
that the natives
have coevolved
with
Character
Displacement
Two species with same
Beak size can not
Coexist on same island
One adaptive result of
resource partitioning
Types of Interspecific Interactions
Species A Species B
Commensalism
+
0
Mutualism
+
+
Competition
-
-
Predation
+
-
Parasitism
+
-
• Commensalism
Predator & Prey
a Mutualism?
Canadian lynx (dashed line)
Snowshoe hares (solid line)
Keystone species
• Pisaster (Sea Star) defends tide pool from
being taken over by mussels, barnacles.
Sea Otters maintain Kelp forest
• Otters are a Keystone
species
• Kelp are the base of the
community
• Urchins eat kelp
• Otters eat urchins
• Otter numbers along
California are dropping.
• Alaska- Orcas starting to
eat otters, because seal
numbers are dropping
• No fish for seals
• Kelp forests
disappearing
Species Richness
• More energy available (productivity) the
species can exist.
• The larger the community size the more
species can be supported.
Number of species of ants
Number of species of breeding birds
Species Richness by Latitude
Island Biogeography Ideas:
• Size of island influences survival rate
– Larger islands sustain more species
• Nearness to other island influences
immigration rate
– Near islands have more species than
distant islands
• “Islands” are any isolated habitat
Island Biogeography
• Larger islands
sustain more
species
Bio Reserve Model
• Core - strict preserve, research.
• Inner Buffer - hiking, Some
commercialization.
• Outer buffer - (may not even be part of
park) camping, concessions, grazing
timber, agriculture.
–
Core
• Round parks
have less edge
effect
Core
– Higher per cent
of park is in core
area
Fig. 23.26, p. 618
Edge effect
• Natural vs. Artificial edges
Bio Reserve Model
• Corridors connect core areas from
park to park forming land bridges
• Our national Forests serve this role
in many areas of the west.
• Few Lager rounded parks, better
than many smaller isolated parks fpr
species richness
Biosphere Reserve
Core area
Inner Buffer
Outer Buffer
Fig. 23.27, p. 620
Hilo
Kona
Naalehu
One Species
Two Species Overlap
Three Species Overlap
Existing Nature Reserves
Fig. 23.28, p. 621
Succession: How the Community
Structure changes over time
• Primary Succession: starts with no
soil, just bare exposed rock
– Progresses in stages until long term
climax stage
• Secondary Succession starts with
the climax vegetation type
– Disturbance (fire) resets timeline
– Progresses in stages back to climax.
Cottonwood and Alders
Spruce moves in
Spruce and Hemlock
Climax Vegetation
Fire is a common disturbance in
grasslands
Fire Cycle
• Community most likely to burn in many areas.
• Many homes now built in these areas.
• Early succession after fire, nutrient limited, mostly
annuals and forbs (herbs) wildflowers.
• Many species are sprouters– Burl survives fire, seeds out new shoots afterwards
• new growth may be very high in protein 14%, deer
and other animals rely on this growth.
• some closed cone pines - need fire to release
seeds.
• Fire follower annual- seeds in soil seed bank
germinate and predominate first few years after
fire
• Shrub canopy closes in about 6 years
Fire poppies in burn area
Madrones sprout from burl
Ceanothus seedlings sprout after fire
1 month
post fire
Schmidts, M.J., D.A.
Sims,
J.A. Gamon
California State
University,
Los Angeles, CA
http://vcsars.calstatela.edu/eas_00/miriam/miriam_esa_00.html
First spring
3 years post fire
20
and 40 years post fire
Aposematic Coloration
Warning I’m poisonous!
Batesian Mimicry
I only look dangerous
Mullerian Mimicry
We both are dangerous
Camouflage
I look like the background