major objectives 1. understand basic community ecology definitions and processes 2. know the two...
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Major Objectives1. Understand basic community
ecology definitions and processes
2. Know the two main hypotheses for why plant communities have different species assemblages
3. Know the 5 potential interspecific interactions between species
4. Know the difference between bottom-up and top-down control mechanisms
What is a Community?A collection of all the populations of
different species that inhabit a particular area.
Communities differ in SPECIES RICHNESS and RELATIVE ABUNDANCE
Beaver (Castor canadensis)
Ecosystem Engineer
Ecosystem Engineer
keystone species
Pisaster spp. is a keystone species
Competitive Exclusion HypothesisTwo species competing for same limited resource can not exist
Individualistic Hypothesis
Why do plant communities have different species assemblages?
A community is the result of chance because of species having similar abiotic requirements
Interactive or "Organismic" Hypothesis
A community is the result of closely linked species locked in by mandatory biotic interactions
Species Interactions
Parasitism
Interspecific Interaction:Predation
• Cryptic coloration, or camouflage
Figure 53.5
• Aposematic coloration– Warns predators to stay away from prey
Batesian Mimicry– A palatable or harmless species mimics an unpalatable or
harmful model
The proportion of carnivore attacks on ringed replicas of scarlet kingsnakes (top left; a mimic of eastern coral snakes) and sonoran mountain kingsnakes (top right; a mimic of western coral snakes) increased with a, latitude (y = - 13.314 + 0.391 x , P < 0.035, R2 = 0.345) and b, elevation (y = - 0.329 + 0.00032 x, P < 0.014, R2 = 0.310). Horizontal dashed line: proportion of attacks on ringed replicas expected under randomness. Vertical dashed line: maximum latitude and elevation for coral snakes in North Carolina and Arizona, respectively.
Frequency-dependent Batesian mimicryDavid W. Pfennig, William R. Harcombe and Karin S. PfennigNature 410 , 323(15 March 2001)doi:10.1038/35066628
Frequency-dependent Batesian mimicryDavid W. Pfennig, William R. Harcombe and Karin S. PfennigNature 410 , 323(15 March 2001)doi:10.1038/35066628
Frequency-dependent Batesian mimicry: David W. Pfennig, William R. Harcombe and Karin S. PfennigNature 410, 323(15 March 2001)
Müllerian mimicry– Two or more unpalatable species resemble each
other
(a) Cuckoo bee
(b) Yellow jacketFigure 53.8a, b
The viceroy (Limenitis sp.; right) and monarch (Danaus sp.) butterflies look very similar but may differ in their palatability to avian predators.
Interspecific Interaction:Herbivory
• The process in which an herbivore eats parts of a plant
Mutualism
Figure 53.9
Mutualism
Commensalism
Competition Life in the shadePlants can tell the difference between the shade of an inanimate object and the shade of another plant. When a plant detects competition from neighboring plants, it initiates a set of responses, called collectively the shade avoidance syndrome, that alter its growth and physiology. A rapid and transient increase of newly synthesized auxin via a newly discovered auxin synthesis pathway allows plants to elongate and grow toward the sun.
Image: Courtesy of Dr. Jean-Luc Ferrer, Salk Institute for Biological Studies
Nuetralism
Species "A"
+
0
-
- 0 +
Species "B"
Species "A"
+ParasitismPredationHerbivory
Commensalism Mutualism
Neutralism Commensalism
Competition ParasitismPredationHerbivory
0
-
- 0 +
Species "B"
No interaction
No interaction
Bottom-Up Control
Top-Down Control
Trophic
Structure
Feeding relationship between organisms
Major Objectives1. Understand basic community
ecology definitions and processes
2. Know the two main hypotheses for why plant communities have different species assemblages
3. Know the 5 potential interspecific interactions between species
4. Know the difference between bottom-up and top-down control mechanisms
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