Community ecology Flashcards
Positive interactions and their benefits, as well as examples
What are positive interactions?
Interactions among 2 or more organisms that positively affects one or more organisms.
E.g. commensalism, mutualism, facilitation
What is true of positive interactions?
Can be:
inter or intraspecific
symbiotic (ecto- and endo-)
obligate/facultative
trophic/non-trophic
direct/non-direct
What are the benefits of positive interactions?
– Habitat-ameliorating: refuge from physical stress
– Associational defence: refuge from predation/competition
– Improves resource availability
– Transport
What is the vertical immersion gradient of Saltmarsh ecosystems?
Dike/dune -> high marsh -> low marsh -> pioneer zone -> unvegetated intertidal mudflat
What is true of Saltmarsh ecosystems?
- Terrestrial and marine biota present
- Ecosystem engineers and biogenic habitats
- Physically stressful environment (burrows as refuge from physical stress -> biogenic habitats created)
- Direct and indirect feedbacks present
What is an example of intraspecific competition and facilitation in rocky shore ecosystems?
– Pear limpet: as density increases, more individuals live on the shells of others
–– Epibionts on epibionts
= Often negative for the one at the bottom (basibiont?)
What is an example of improved resource availability?
CORAL REEFS:
– Coral polyp–zooxanthellae association
= Obligate mutualism and trophic interactions
Zooxanthellae provide nutrition to the corals in the form of photosynthate, in exchange for nitrogen in coral waste products
What is an example of transport benefits?
CORAL REEFS:
– Solitary coral and hermit crab: obligate mutualism
= crab has associational defence, coral has transport and habitat amelioration
What is the intermediate disturbance hypothesis?
Larger boulder- rarely overturned
Small boulders- frequently overturned
Medium boulders- intermediate overturning
