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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--effects of distance from the mainland and size of an island on community diversity. Conclusions? Model of Island Biogeography Habitat and Ecological Niche Habitat -- Home. Ecological niche ---occupation in the community 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 decreases competition. 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 – Harmless mimics harmful 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 pioneering plant retreating glaciers leave moraines. autotrophic mosses and lichens are species are next first macroscopic bacteria are first autotrophs. soil forms colonizers. gradually 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