1. Community Ecology
-Types of Species
-Species Interactions

2. General Types of Species
Examining roles of various species in ecosystems:
Native species = a species that, other than as a result of an introduction, historically occurred or currently occurs in an ecosystem (Indigenous)
Invasive species = an alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health. (non native species, exotic, introduced etc.)

3. Some characteristics of Invasive Species:
High rate of reproduction
“pioneer species”
High dispersal rates
Tolerant of a wide range of conditions
Generalist
Impact on native ecosystems
Invasive species impact 30-50% of the species currently listed as Threatened or Endangered under the U.S Federal Endangered Species Act.
(Second only to habitat destruction.)

4. Examples of Non-natives (Invasive)
Non-native herbivores, like gypsy moth, directly affect the flow of energy captured by plants from the sun. 
Non-native earthworms can dramatically increase decomposition in soils.
Non-native bee species (killer bees)
Rats (Sandy Cay)
Cane Frog (Tortola)

5. Keystone species
….play pivotal roles in the structure, function, and integrity of an ecosystem… affect the health and survival of other species.
Their strong interactions with other species, and the fact that they process material out of proportion to their numbers makes them a Keystone Species.

6. Keystone Species Critical roles Include:
Pollination of flowering plant species by bees, hummingbirds, bats
Dispersion of seeds by fruit eating animals
Predation by top carnivores to control the populations of various species
Habitat modifications: bats and birds regenerate deforested area by depositing plant seeds in their droppings
Loss of keystone species can lead to pop. Crashes and extinction of species that depend on it for certain services.

7. Indicator Species
Can be described as species that serve as early warnings that a community or an ecosystem is being damaged or not stable.
One example would be:
Apex species (top carnivores or top predators)
Are always the first to be affected by any change in their ecosystems and therefore, how their numbers indicate the health of the ecosystem

8. Birds as Indicator Species
Birds are excellent bioindicators because they are found almost everywhere, and they respond quickly to environmental change.
Migratory paths
Habitat loss and fragmentation

9. Amphibians

10. The indicators for Tropical Caribbean eco-region (Marine)
Species: All Sharks
Blacktip shark Carcharhinus limbatus Blacktip reef shark Carcharhinus melanopterus Blue shark Prionace glauca Bull shark Carcharhinus leucas Caribbean reef shark Carcharhinus perezi Great hammerhead shark Sphyrna mokarran Carcharhinus perezi Grey reef shark Carcharhinus amblyrhynchos Lemon Shark Negaprion brevirostris Nurse shark Ginglymostoma cirratum Tiger shark Galeocerdo cuvier Whale shark – Vulnerable Rhincodon typus

12. Species: All Marine Turtles
Most experts recognize seven species of marine turtles: the green, hawksbill, loggerhead, Kemp's ridley, olive ridley, leatherback, and flatback. All but one - the flatback - can be found in the Latin American and Caribbean region, and all are threatened by extinction.

13. Community structure
Community~ an assemblage of populations living close enough together for potential interaction
Richness (number of species) & abundance…….
Species diversity
Hypotheses: •Individualistic~ chance assemblage with similar abiotic requirements
•Interactive~ assemblage locked into association by mandatory biotic interactions

14. Species Interactions: Predation
Predator: feeds directly on all or part of a living organism
Prey: organism fed on.
Predator-prey relationship: One organism is clearly harmed. However at the population level there are benefits: improve access to food, and improve the genetic stock.
Prey acquisition: herbivores vs. carnivores (pursue or ambush)
Predator Avoidance: speed, highly developed senses,protective coverings

15. Predator Avoidance by Prey
Chemical warfare
camouflage
camouflage
Warning coloration
Chemical warfare
mimicry
Warning coloration
Deceptive looks
Deceptive behavior

16. Predation defense Cryptic (camouflage) coloration
Aposematic (warning) coloration
Mimicry~ superficial resemblance to another species √ Batesian~ palatable/ harmless species mimics an unpalatable/ harmful model √ Mullerian~ 2 or more unpalatable, aposematically colored species resemble each other

17. Symbiotic Relationships
Symbiosis is a relationship in which species live together in an intimate association.
There are three types:
Parasitism (special form of predation)
Mutualism
Commensalism

18. Interactions Interspecific (interactions between
populations of different species within a community):

20. Symbiotic Species Interactions: Mutualism
Reproductive mutualism: pollination
Nutritional mutualism
Nutritional/protection mutualism
Fig p. 179

21. Symbiotic Species Interactions: Commensalism
Indirect: i.e., small plants growing in shade of larger plants (redwood sorrel)
Direct: i.e., epiphytes (orchids and bromeliads), remoras
Fig p. 180

22. Symbiotic Species Interactions: Parasitism
Parasite: organisms that feeds on another by living in or on another living organism. Parasite benefits.
Host: Organism that a parasite feeds on and lives in or on. Host is harmed. (rarely killed)
Endoparasites: parasites found inside the host organisms body. Ex.tapeworms,disease causing microorganisms.
Ectoparasites: organisms found outside the host organisms body. Ex. Fleas, ticks, mosquitoes

23. Species Interactions: Competition
Intraspecific competition: within a species for resources and territoriality.
Interspecific competition: between different species for limited resources (niche overlap)
Competing species must:
Migrate to another area
Shift its feeding habits or behavior through evolution and natural selection
Suffer a sharp decline in population
Extinction

24. Species Interactions: Competition
Interference competition:
One species influences another’s access to some resource regardless of its abundance. Ex. hummingbird
Exploitation competition:
Two competing species have roughly equal access but differ in how fast or efficiently they exploit it.

25. Competition: a closer look
Competitive exclusion principle: by Gauss describes how one species eliminates another in an area through competition for limited resources.

26. Competition evidence
Resource partitioning~ sympatric species consume slightly different foods or use other resources in slightly different ways
Character displacement~ sympatric species tend to diverge in those characteristics that overlap
Ex: Anolis lizard sp. perching sites in the Dominican Republic
Ex: Darwin’s finch beak size on the Galapagos Islands

27. Resource partitioning

28. Resource Partitioning
Resource partitioning: a method to reduce competition, dividing up the resource so that species with similar needs use them at different times, in different ways, or in different places.
Fig. 8-9 p. 175; Refer to Fig p. 152 & Fig p. 175

29. The Niche
Ecological niche~ the sum total of an organism’s use of biotic and abiotic resources in its environment; its “ecological role” √ fundamental~ the set of resources a population is theoretically capable of using under ideal conditions √ realized~ the resources a population actually uses
Thus, 2 species cannot coexist in a community if their niches are identical
Ex: Barnacle sp. on the coast of Scotland