Community Ecology Chapter 47

Outline         Diversity and Composition Models Island Biogeography Habitat and Ecological Niche Competition Between Populations Predator-Prey Interactions Symbiotic Relationships Community Development Community Diversity

Community Concept   What is a community?

Factors to consider   Composition is a listing of various species in the community.

Diversity includes both species richness and species diversity.

Diversity and Composition Models   Gleason  Individualistic Model Each population in community is there because its own particular abiotic requirements are met by a particular habitat.

Clements  Interactive Model Community is the highest level of organization.

 Dependent on biotic interactions.

Island Biogeography   MacArthur and Wilson community diversity.

--effects of distance from the mainland and size of an island on Conclusions?

Model of Island Biogeography

Habitat and Ecological Niche   Habitat -- Home.

Ecological niche community ---occupation in the  Fundamental niche - potential  Realized niche - actual

Feeding Niches for Wading Birds

Species interactions

 Community interactions can be potent selective pressures  Competition  Intraspecific  Interspecific  Predator/Prey  Symbiosis

RESULTS OF INTERACTION  (+) organism benefits (how?)  (-) organism suffers (how?)  (0) neutral, no benefit or loss (RU sure?)

Competition Between Populations   Intraspecific competition (?) Interspecific competition (?)  Competitive Exclusion Principle  Resource Partitioning competition.

decreases  Can lead to character displacement .

Resource Partitioning –more specialized niches

Competition Between Barnacle Species

Character Displacement in Galápagos Finches

Predator-Prey Interactions  Predation  Selective pressure?

  Interaction = +, Population effects

Lynx-Snowshoe Hare Interactions

Prey Defenses  Prey defenses -adaptations that thwart the possibility of being eaten by a predator.

     Concealment/cryptic coloration/other coloration Warning coloration Armor/weaponry Chemicals Behavior

Gecko Gecko?

Gecko?

Stoneplant

Walking stick

Camouflage in the Anglerfish

Mimicry  Mimicry occurs when one species resembles another that possesses an overt antipredator defense.

 Batesian harmful – Harmless mimics  Müllerian – Harmful mimics harmful

Batesian I: Coral snake or Milk Snake? Would you bet your life on it?

Batesian or Mullerian?

Vertebrate Eye Mimicry

 Similar to Batesian  Can startle or confuse predator

Eye Mimicry 2

Aposematic (Warning) Coloration

Chemical Defenses

Chemical Defenses 2

Deceptive Coloration Example

Sea Hare

PHAGOMIMICRY

Symbiotic Relationships  Symbiosis close relationship between members of two populations. We’ll be interested in 3:  Parasitism (+, -)  Commensalism (+, 0)  Mutualism (+,+)

Parasitism (+, -)  Endoparasites Ex?

 Ectoparasites EX?  Social Parasites  Brood parasites  Kleptoparasites

Endoparasite Life cycles  Complex, spend different stages in different hosts 

Definitive host (primary host)



Intermediate host

Tapeworm Life Cycle

Schistosomiasis

Elephantiasis

Brood Parasitism- European Cuckoo  The behavior of the cuckoo hatchling ejecting the host eggs from the nest  The feeding behavior of a foster mother to the cuckoo chick Figure 37.3B

Kleptoparasite—Red Billed Gull

 

Commensalism --+, 0

Shark (0) Remora (+)

Pseudocopulation Some orchids offer no nectar at all, but they resemble the female of various insect species. Or at least, resemble closely enough to fool a desperate male of the species – the mimicry is chemical as well as visual. The unfortunate male has to be deceived twice and engage in two acts of pseudocopulation before pollination takes place. Common european species doing this are the bee orchids in the genus

Ophrys

. In fact some populations of bee orchid seem to be self-fertile in the absence of pollination.

Bee orchid

Ophrys apifera

Mutualism

   Mutualism (+,+) both members of the association benefit.

ADVANTAGES?

EX?

Mutualism Between Bullhorn Acacia and Ants

Cleaning Symbiosis

Community Development  Ecological Succession  A change involving a series of species replacements in a community following a disturbance.

 Primary Succession  Secondary Succession  Pioneer Species  Climax Species

Secondary Succession in a Forest

Succession Models  Facilitation Model  Succession in a particular area will always lead to the same type of community  Climax Community—Endpoint of succession  Oldest, most supported

Changes in soil structure over time Soil changes over time.

Nitrogen levels start out low and increase because of symbiotic nitrogen-fixing bacteria in alder.

Then other trees can survive.

Succession Models   Inhibition Model  Colonists hold onto their space and inhibit growth of other plants until the colonists are damaged or die.

Tolerance Model  Different types of plants can colonize an area at the same time.

 Chance determine which seeds arrive first.

Ecological succession: Primary succession

retreating glaciers leave moraines. autotrophic bacteria are first colonizers.

mosses and lichens are first macroscopic autotrophs. soil forms gradually pioneering plant species are next

Succession continues until a climax community is formed.

spruce replace alder and cottonwood final stage is a spruce and hemlock forest

Secondary succession occurs after disturbance that leaves the soil intact. Other examples?

Fig. 53.18 – 1988 fires in Yellowstone

Community Diversity  Community stability can be recognized in three ways.

   Persistence through time.

Resistance to change.

Recovery once a disturbance has occurred.

Intermediate Disturbance Hypothesis  Moderate amounts of disturbances at moderate frequency are required for a high degree of community diversity.

 If widespread disturbances occur frequently, diversity will be limited.

Intermediate Disturbance Hypothesis

Predation, Competition, and Biodiversity   In certain communities, predation by a particular species reduces competition and increases diversity.

 Predators that regulate competition and maintain community diversity are referred to as keystone predators.

Introduction of exotic species into a new area may lead to unbridled competition and resultant reduction in biodiversity.

Predation, Competition, and Biodiversity   In certain communities, predation by a particular species reduces competition and increases diversity.

 Predators that regulate competition and maintain community diversity are referred to as keystone predators.

Introduction of exotic species into a new area may lead to unbridled competition and resultant reduction in biodiversity.

Review         Diversity and Composition Models Island Biogeography Habitat and Ecological Niche Competition Between Populations Predator-Prey Interactions Symbiotic Relationships Community Development Community Diversity