made up of the populations of different species that live together in a particular place and interact with one another.
community
often used in a narrower sense to refer to a subset of the species, such as a plant, bird, or fish community,
Cunningham and Cunningham (2007)
communities have emergent properties which are as follows:
(1) species diversity,
(2) community structure,
(3) resilience, and
(4) stability.
Smith and Smith (2009)
also consider the nature of species interactions in the community as an emergent property of communities.
Species diversity
Refers to the number of different species in a community combined with either species richness and/or species abundance
Species richness abundance or number of individuals of the different species
Tropical areas have greater species richness since it can support more life
Species evenness, number of individuals of the different species making up a community (Miller & Spoolman, 2009).
proportion or relative abundance of each species
if the number of individuals vary there is a greater diversity, hence low species evenness can be observed
A community where the number of individuals of the different species are nearer to each other has a higher species evenness than one where there are much more of some species compared to others.
True or False: Most species are, thus, moderately abundant (True)
A tropical forest has a large number of different species but generally have few individuals of each species.
A coniferous forest may have only small number of species but a large number of each species.
Coniferous forest has low species richness and high species evenness
Tropical forest has high species richness and low species evenness
Microenvironments has many niches. If there are many niches, it has many species that occupy the area.
Environmental heterogeneity
One of the most important factors in species diversity
It means more resources, more niche and more refuges.
Robert MacArthur
one of the first ecologists to quantify the relationship between environmental heterogeneity and species diversity.
Robert MacArthur and John MacArthur (1961)
studied vegetative communities ranging from grasslands to mature deciduous forests.
They found out that plant communities with greater foliage height diversity supported more diverse bird communities
Foliage height diversity increases with species richness and species evenness
species richness
which determines the number of vegetative layers
species evenness
how evenly vegetative biomass of different tree species is distributed among layers
Foliage height diversity increases with species richness and species evenness
species richness
which determines the number of vegetative layers
species evenness
how evenly vegetative biomass of different tree species is distributed among layers
For plants, variation in physical and chemical conditions, such as temperature, moisture and availability of soil nutrients contribute to environmental complexity.
Inverse relationship in plants
More fertile soil has less species compared to soil that has less nutrients.
In less fertile soil, it has more plants but it is less competitive compared to those in fertile soil that has a dominant plant that is more competitive.
Huston (1979)
examined the relationship between species richness and soil fertility (percentage of phosphorus, potassium and calcium) in 46 sites in tropical rainforests in Costa Rica
found an inverse relationship between species richness and soil fertility.
More fertile soils supported a smaller number of tree species than soils with less nutrients available.
Tilman et al. (1982)
conducted an experiment similar to Gause’s on competition between two Paramecium species.
Tilman grew two species of diatoms: Cyclotella meneghiniana and Asterionella formosa
The implication of this finding is that if the silicate:phosphate ratios vary across a lake, then there is higher environmental heterogeneity that influences species diversity of diatoms and their consumers (Molles, 2013).
Physical structure of a community
refers to the pattern of spatial distribution of individuals and species in a community (Cunningham and Cunningham, 2007).
Zonation (Smith and Smith, 2009).
The changes in the physical and biological structures of communities as one moves across the landscape.
Trophic structure
refers to the feeding relationships among the species of a community
these relationships are summarized in a food web
food web
formed by several simple, straight-line food chains that are shown as interconnected in a diagram
Basal species
species that do not feed on other organisms but are fed upon by other organisms
Intermediate species
feed on the other species and are also fed upon by other species
Top predators
feed on intermediate and basal species and do not have predators (Smith and Smith, 2009).
Keystone species
great importance to food web
Guilds
Organisms that obtain the same general kind of food depending on the way they feed.
ToF: Members of a guild belong to different species and even kingdoms but they obtain food in similar ways (True)
Functional Types
Classifying organisms in a community based on their responses to the environment or role in the community rather than taxonomy.
Photosynthetic pathway
C3
C4
CAM
Adaptations to light
Shade-tolerant
Shade-intolerant
Timing of reproductive effort
Semelparous
Iteroparous
(Paine) The species with the strongest influence on the community structure as the keystone species.
One of the most commonly introduced groups of organisms are fish.