1. organism
population
Community Ecology
community
ecosystem
biosphere

2. Community Ecology Community Community Ecology
all the organisms that live together in a place
Community Ecology
study of interactions among all populations in a common environment
To answer:
In what way do the populations interact?

3. Niche An organism’s niche is its ecological role
habitat = address vs. niche = job
High tide
Competitive Exclusion
If Species 2 is removed, then Species 1 will occupy whole tidal zone. But at lower depths Species 2 out-competes Species 1, excluding it from its potential (fundamental) niche.
Species 1
Low tide
Chthamalus sp.
Species 2
Fundamental
niches
Realized
niches
Semibalanus sp.

4. Niche & competition Competitive Exclusion Prinicple
No two similar species can occupy the same niche at the same time

5. Resource partitioning
Reduce competition through microhabitats
Resource partitioning among Dominican Republic lizards. Seven species of Anolis lizards live in close proximity, and all feed on insects and other small arthropods. However, competition for food is reduced because each lizard species has a different perch, thus occupying a distinct niche.
Sympatric species often partition available resources, reducing competition between them.

6. Community Relationships
Symbiotic interactions
competition (-/-)
predation / parasitism (-/+)
commensalism (+/0)
mutualism (+/+)
lichens (algae & fungus)
“Freddy fungus and Annie algae took
a Lichen to each other!”

7. Symbiosis
mutualism
+/+
commensalism
+/0
predation
+/-
competition
-/-

8. Predation drives evolution
Predators adaptations
locate & subdue prey
Prey adaptations
elude & defend
Predation provides a strong selection pressure on both prey & predator
horns, speed, coloration
spines, thorns, toxins
Predation provides a strong selective pressure on prey populations. Any feature that would decrease the probability of capture should be strongly favored.

9. Anti-predator adaptations
Hiding from predators
avoid detection
camouflage
Warning coloration
advertise how undesirable you are as prey
Aposematic coloration
apo = away & sematic = sign/meaning
Batesian mimicry
Mullerian mimicry

10. Common warning coloration
Aposematic species come to resemble each other
black, red, orange & yellow means: DON’T EAT ME!

11. Batesian Mimicry Convergent evolution green parrot snake
palatable or harmless species mimics a harmful model
green parrot snake
Hawkmoth larva puffs up to look like poisonous snake
hawkmoth larvae

12. Which is the moth vs. the bee? Which is the fly vs. the bee?
Nonpoisonous Mimic!
Batesian mimicry
Viceroy male
edible
Monarch male
poisonous
Which is the moth vs. the bee?
Which is the fly vs. the bee?
fly
bee
moth
bee

13. Mullerian mimicry cuckoo bee yellow jacket
two or more poisonous species look like each other
cuckoo bee
yellow jacket
- group defense?
- predators may evolve innate avoidance

14. Coral snake is poisonous
What kind of mimicry?
Coral snake is poisonous
King snake is not
Red on yellow, poison fellow; red on black, safe from attack

15. Coevolution in Community
Predator-prey relationships
Parasite-host relationships
Flowers & pollinators
Long term evolutionary adjustments between species

16. Predator/Prey Coevolution…

17. Community Structure Species diversity Ecological Succession
How many different species?
Who’s dominant?
most abundant or highest biomass (total weight)
Keystone species
Ecological Succession

18. Species diversity greater diversity = greater stability
Greater biodiversity offers:
more food resources
more habitats
more resilience in face of environmental change

19. The impact of reduced biodiversity
compare these communities
suburban lawn
agricultural “monoculture”
“old field”
In the early 1970's, a new corn genotype was released in the US; the "Texas male sterile" (TMS). Hybrids that contained this new characteristic had many desirable properties, and growers were excited about them, planting them over miles and miles of corn acreage in US. They were, of course, bred to be resistant to the most common corn diseases. However, they were not resistant to a previously unimportant strain of a fungal disease; the southern corn leaf blight (caused by the fungus Helminthosporium maydis). Ninety percent of the corn sowed in the US in 1970 contained the TMS trait and also shared genetic susceptibility to this pathogen. The fungus encountered all this acreage of susceptible host and wiped out one fourth of the US corn crop in 1970, a loss of over one billion dollars in production! If the corn acreage hadn't been such a monoculture, the fungus wouldn't have been able to spread as rapidly, as it would have encountered barriers of genetically resistant plants.
Irish potato famine
1970 US corn crop failure

20. Keystone species Influential ecological role
A species that has a large effect on its environment relative to its abundance
A consumer organism (herbivore or carnivore)
Low biomass in numbers

21. What would be the impact of the Orca whale?
Keystone species
Sea otter is a keystone predator in North Pacific
Structure of a community may be controlled bottom-up by nutrients or top-down by predators
What would be the impact of the Orca whale?

22. Keystone Species
diversity increases
diversity decreases
mussels out-compete other species
Following the removal of Pisaster, richness fell from 15 to 8 species
Pisaster promotes species diversity by preventing competitive exclusion by Mytilus