How does the form of growth influence community structure? (Type of growth)
Determines the spatial structure of the community
- spatial & temporal availability of resources
- microclimate
- spatial complexity
- potential for disturbance
Species abundance
The number of species in a given area/environment
- A species is considered abundant when it has a high population relative to the size of the area it inhabits
What does it mean to be diverse?
Species are not equally abundant
How do dominant species effect other species?
It affects the distribution and survival of other species
Species Richness
A measure of the number of different types of species in an ecosystem
- A large number of different species in a habitat represents a higher species richness, and an overall more diverse ecosystem
Species Evenness
The relative abundance/amount of each species
alpha (a symbol)
Diversity of species within a small area (community)
beta (b symbol)
Species diversity between two communities or ecosystems.
gamma diversity (y symbol)
Species diversity across communities within a larger geographic area
Environmental complexity and species diversity
Positive relationship between complexity and species diversity
- Changes in soil type causes differences in vegetation (Tree height) over a short distance (Trees) - can be caused by fertilization
Where are hot spots of species diversity located?
- Tropics
- Mediterranean-type systems
- Mountainous areas
Character displacement
- Occurs when similar species that live in the same geographical region and occupy similar niches differentiate in order to minimize niche overlap and avoid competitive exclusion
- The height of a tree height allows different species of birds to locate in different areas of the trees = species diversity (Character displacement)
Niche breadth
- The diversity of resources used or environments tolerated by an individual, population, species, or clade
- The range of conditions under which an organism can live
Niche separation
- The process by which competing species use the environment differently in a way that helps them to coexist.
Why is predation / scavenging important?
Leads to an increase in plant species diversity because the dispersal of seeds occurs when animals eat seeds from plants
Keystone predator
Species in which an ecosystem largely depends on that species, so much that if it were to be removed, the ecosystem would change drastically
Intermediate disturbance hypothesis
Species diversity is maximized when environment disturbance is neither too rare nor too frequent (Peak represented in the graph)
Closer to 0, low levels of disturbance
Diverse communities display?
More productivity, higher resource efficiency (most stable)
Diverse communities are less susceptible to what?
The invasion of non-native species and less susceptible to a variety of disease outbreaks
What are the effects of invasive species on community structure?
They cause a decline or extinction of native species
How do invasive species cause local extinction of native species?
- Competition
- Predation, pathogenicity, parasitism
- Habitat alteration
Parasitism
A relationship between the two living species in which one organism is benefitted at the expense of the other (Parasite and host)
Pathogenicity
The capacity of a microbe to cause damage in a host
What do invasive species do to ensure they succeed in new environments?
They have to escape from predators in the environment with the ability to modify new environment are keys to invasion success
