1. Explain the link between Biodiversity and
2. Determine the disturbance factors that
contributes to the variation of species in a
3. Explain the Intermediate Level of
“Are diverse communities more stable
“Are stable systems more diverse than
Factors that affects species diversity:
1. Invasive Species
2. Keystone Species
3. Availability of
4. Stability of Community
“How do say that an environment is stable or
What is disturbance in the aspect of
• Is a temporary change in average
environmental conditions that causes a
pronounced change in an ecosystem.
• Disturbances often act quickly and with great
effect, sometimes resulting in the removal of
large amounts of biomass.
“Are diverse communities more stable than
“Are stable systems more diverse than unstable
Intermediate Level of Disturbance
• Joe Connel (1978), the highest local diversities
are actually maintained NOT in stable systems
but in communities of levels of disturbance.
• High level of Disturbance:
– Only good colonists (r-selected species) will
survive giving rise to low diversity.
• Low Level of Disturbance:
– Competitively dominant species will out compete
all other species and only a few k-selected species
will persist, yielding low diversity.
Most Diverse lies in between. Hence, Intermediate.
• Examples of communities with High species
– Rain Forest (diversity maintained by storms)
– Coral Reefs (Diversity maintained by Hurricanes)
Seth Reice (1994)
• Disturbance operates in habitats of all types
and naturally disturbed areas are nearly
always more diverse than undisturbed areas.
• Many communities exist in nonequilibrium
state in which the species composition
Wayne Sousa (1979)
• Small boulder – 1.7 sessile plants/animal sp.
• Large Boulder – 2.5 sp.
• Intermediate Boulder – 3.7 mean sp k and r
~Rock Stability vs. Rock Size
• The most diverse communities are not
necessarily the stable. Rather, the most
diverse communities seem to exist at
intermediate level of disturbance.