Community Ecology Chapter 54

Interspecific Interactions Competition --/-- Competitive exclusion Ecological Niches (Habitat-address; niche- profession) Resource partitioning-allows similar species to coexist in a community Fundamental niche-potential Realized niche-actual-may be result of interspecific competition

Character Displacement Tendency for characteristics to diverge more in sympatric pop of 2 species than in allopatric pop

Predation +/-- Can be animal eating plant tissues Defensive adaptations –Cryptic coloration

Aposematic coloration- warning

Batesian mimicry-harmless or palative looks bad

Mullerian mimicry 2 unpalatable species look alike

Herbivory +/-- Plants have chemical toxins, spines, thorns ex strychnine, nicotine, selenium toxins Herbivores-special adaptations –Insect-chemical sensors –Sense of smell –Specialized teeth –Length of digestive systems

Symbiosis Parasitism +/-- Mutualism +/+ obligate; facultative Commensalism +/0

Species Diversity Species richness Relative abundance

Shannon diversity (H) Index based on species richness and relative abundance

Trophic structure Food Chain

Food Webs (Elton 1920s)

Limits on length of food chain Energetic hypothesis-inefficiency of energy transfer -10% rule Dynamic stability hypothesis-long food chains are less stable than short ones- population fluctuations at lower trophic levels are magnified at higher levels Also-carnivores tend to be larger at successive trophic levels-can’t get enough food to meet needs

Dominant species Most abundant-have the highest biomass Exert a powerful control Are they are competitively superior in exploiting limited resources? Are they are most successful at avoiding predation?-would explain effect of invasive species…

Invasive pressure American Chestnut Before % of US trees-fungal disease- Chestnut blight-killed all the trees-oak, hickory replaced; mammals, birds ok, but 7 species of moths and butterflies became extinct

Keystone species

Foundation species Ecosystem “engineers” Affect by causing physical changes in the environment Ex beavers Facilitators-may help other species

Models of organization Bottom upV  H N  V  H  P Top down V  H N  V  H  P Trophic Cascade Biomanipulation-prevent algal blooms by adding consumers rather than chemicals

Disturbance Influences species diversity and composition Storms, waves, fires, freezing, drought, Moderate disturbance can foster greater diversity than low or high levels

Ecological succession Species are replaced by other species Primary Secondary Climax community

Island Equilibrium Model

Detritivores Return nutrients to the soil Law of conservation of mass

Aquatic Ecosystem Light limitation Nutrient limitation Eutrophication

Biomass-dry mass

Phytoplankton continually replace their biomass at such a rapid rate, they can support a biomass of zooplankton bigger than their own biomass.

The Green World Hypothesis Terrestrial herbivores are held in check by a variety of factors.

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Productivity GPP-gross primary production NPP-net primary production NPP=GPP – R(autotrophic respiration) Primary production –in aquatic is mostly affected by light and nutrients-N and P –Eutrophic-nutrient rich –On land-temp and water –evotranspiration

Biogeochemical cycles

Nitrogen cycle

Additional Terms Bioremediation-use of organisms to detoxify polluted areas Bioaugmentation-add desirable species such as nitrogen fixers Biodiversity (3 Levels)-genetic diversity, species diversity and ecosystem diversity Threats: habitat loss, introduced species, over-harvesting, global change

Population conservation Focuses on: –Population size –Genetic diversity –Critical habitat

MVP Minimum Viable Population Extinction Vortex

Landscape and regional conservation Habitat fragmentation Movement corridors Biodiversity hot spot-small area with an exceptional concentration of endemic species

Human Actions Agriculture-nutrient cycling-take it out of soil or too much in water Acid precipitation Biological magnification Greenhouse effect Global warming Ozone layer

Elements