Community Ecology (W11) Flashcards
List of Models that explain the nature of communities? (2)
• Organismic model.
• Individualistic model.
Organismic model attributes? (3)
• Plant communities are closely integrated systems with numerous “emergent properties”, and are analogous to a “super-organism”.
• Communities function as an organism & ultimately mature (climax community).
• Climatic climax communities.
Individualistic model attributes? (6)
• Emphasises species individuality with each having its Abiotic living requirements.
• Communities are there by chance.
• Don’t function as an organism.
• Chance occurrence of species that have similar ecological requirements.
• Emphasises environmental gradient nature of communities.
• Juxtaposition of individuals of the same/different species.
Explain Organismic model graph?
Explain Individualistic model?
Succession?
= the evolution of community structure over time leading to a stable community.
Succession attribute?
Communities develop gradually during this process.
Types of succession? (2)
• Primary succession.
• Secondary succession.
Primary succession?
= occurs in a lifeless area (soil-forming processes with no seed bank or reserve for vegetative propagules in the substrate).
Secondary succession?
= occurs in areas after disturbances (small-scale disturbancessuch as fire in grasslands, or flooding event).
Primary succession process?
Secondary succession process?
Paper to read for Observed patterns of succession?
Olivier et al, 2012.
Mechanisms fo plant succession? (3)
• Facilitation hypothesis.
• Tolerance hypothesis.
• Inhibition hypothesis.
Facilitation hypothesis?
= early species prepare ground for later species.
Tolerance hypothesis?
= early species modify the environment, but it does not affect the recruitment & growth of later species.
Inhibition hypothesis?
= early colonists secure the space/resources & thus inhibit the invasion of subsequent colonists.
Resource Ratio model of succession attributes? (2)
● Assumes that each plant species is a superior competitor for a particular proportion of the limiting resources.
● Predicts that community composition should change whenever the relative availability of two or more limiting resources changes.
Disturbance?
= events that change the biological communities by removal of nutrients.
Disturbance attribute?
Influences succession & species richness.
Explain how Disturbance influences succession & species richness? (2)
• Low disturbance, late successional species dominate.
• High disturbance, allows early successional species to persist.
Hypothesis for Disturbance?
Intermediate disturbance hypothesis (IDH).
Explain Intermediate disturbance hypothesis graph? (6)
● x-axis = disturbance frequency and/or amplitude.
● y-axis = species diversity.
● Dotted line = exponential decrease.
● Dashed line = exponential increase.
● Solid upside down U.
● All lines cross each other.
Explain IDH graph:
Dotted line? (4)
• Low DEM (growth rate).
• Low disturbance at high point.
• Starts at y axis.
• Ends at tip of solid upside-down U.
Explain IDH graph:
Dashed line? (4)
• High DEM (growth rate).
• High disturbance.
• Starts at tip of solid line (left).
• Ends at right.
Explain IDH graph:
Solid upside-down U line? (3)
• Intermediate growth rate (IDH = DEM).
• Moderate disturbance.
• High species richness.
Explain The IDH & Plant invasion graph? (6)
● x-axis
= ¹ disturbance frequency (low to very high).
² strength of competition (high to very low-left to right).
● y-axis = species diversity (low to high- bottom to top).
● Two graphs that why you have 2 x-axes.
● Light line = historical disturbance gradient.
● Dark line = human disturbance.
● Dashed line = diversity of an alien plant in high disturbance.
Hypothesis relating to Invasive species?
The Invasibility theory.
Invasibility theory?
= a plant community becomes more susceptible to invasion wherever there is an increase in the number of unused resources.
Invasibility?
= the susceptibility of an environment to invasion by non-resident species.
Invasibility theory attributes? (2)
• Agrees with Gleason’s idea of the nature of a community.
• Fargione & Tilman, 2005.
Interactions among communities?
= when members in a community engage in interspecific interactions.
Interspecific interactions?
= relationships with individuals of other species in a community.
Interspecific interactions attribute?
May have a helpful or harmful impact.
Interspecific competition?
= negative interaction between two or more species in the same guild or trophic level.
Interspecific competition attribute?
Manifests itself to reduce abundance & fitness of the other species.
Why does interspecific competition manifest? (2)
• To reduce the abundance of the species.
• To reduce the fitness of the other species.
Competition?
= occurs when two or more species want to use the same resource at once.
Competitive exclusion hypothesis?
= when competition between between species with overlapping niche may lead to competitive exclusion.
Competitive exclusion person?
Gause.
Mechanisms of interspecific competition person?
Schoener.
Mechanisms of interspecific competition? (6) [COPATE]
• Consumption.
• Overgrowth.
• Preemption.
• Allelopathy.
• Territoriality.
• Encounter competition.
Consumption?
=
Eg of Consumption?
Competition between granivorous rodents & ants for seeds.
Overgrowth?
= when one organism grows directly over another, with or without physically contacting the other organism.
Preemption?
= occurs when a physical resource, like an open space required for settlement, is occupied by one organism & made unavailable to others.
Where does Preemption occur?
Among sensible organisms.
Eg of Overgrowth?
Eg of Preemption?
Allelopathy?
= interaction using chemicals which allow a plant to compete better in an environment.
Eg of Allelopathy?
Invasive plants (Lantana).
Territoriality?
= results from the aggressive behavioural exclusion of organisms from specific units of space that are defended as territories.
Eg of Territoriality?
Lions.
Encounter competition?
= occurs when non-territorial encounters between foraging individuals result in negative effects on one or both of the interacting individuals.
Eg of Encounter competition?
Adaptations to reduce competition? (2)
• Resource partitioning.
• Character displacement.
Resource partitioning?
= natural selection that will force competitors to use resource differently.
Resource partitioning attribute?
It’s a way to avoid competition between species & allow for coexistence.
Egs of Resource partitioning? (3)
• Warbler birds in trees.
• Plant roots.
• Anolis lizards.
Explain Warbler birds in the tree?
Where the different warbler birds use different sections of the tree to avoid competition.
Explain Plant roots? (2)
● Relates to varying soil depths.
● Smart weed roots (deep); Indian mallow roots (middle) & Bristly foxtail roots (shallow).
Explain Anolis lizards? (3)
● Dominican Republic lizards occupy different preferred porches.
● One on perches on shady branches (A. insolitus).
● One on fence posts & other sunny surfaces (A. distichus).
Character displacement?
= trait evolution stemming from selection to lessen resource competition between species.
Character displacement attribute?
Acts on traits associated with resource use.
Egs of Character displacement? (3)
• Morphological structures such as beaks & jaws.
• Galapagos finches.
• Mussels (barnacles).
Explain Galapagos finches?
Initially, one finch from Los Hermanos with a small beak and one from Daphne Major islands with a large beak occur separately (allopatric) but when both occur in the same area, San Cristobal islands (sympatric), the former develops a smaller beak size than before & the latter one develops a larger beak than before.
Explain Mussels (barnacles)? (2)
● Niche separation in space.
● Chthalamus & Semibalanus, where the former is higher up (dominant) in the tide, while the latter is lower down (dominant) in the tide.
Fundamental niche?
= conditions & resources that are available to an organism in the absence of interaction with other organisms.
Realized niche?
= conditions & resources that are available to an organism in the presence of interacting species (competitors & predators).
Fundamental niche is AKA?
Where they CAN occur.
Realized niche is AKA?
Where they CHOOSE to occur.
