terms 2 Flashcards
communities are defined by:
taxonomic affinity
guild (specis that use the same resource)
functional group (species that function in similar ways eg nitrogen fixing plants)
what is a guild
species that use the same resource eg flower feeders
what is a funtional group
species that function in similar ways eg nitrogen fixing plants
key elements of comunity structure are:
species composition
species ecological inter-relationships
species diversity
species diversity
combines two aspects of a comunity: species richness and species evenness
species richness
the number of speces in a comunity
species evenness
relative abundances compared with one another
Shannon index
H= - sum of all proportion of individuals in the ith from species times ln(proportion of individuals in the ith species)
what is the maximum value for evenness?
1
Speces accumulation curve
species richness plotted as a function of total number o findividuals counted
help determine when most of all of the soecies in a commuity have been observed
most cases the hreshold where no new speces are counted is never found b/c there are always new, rare specesis to add
species-area relationship
species richness increases with area sampled (assuming simialr effort eg similar number of individuals sampled in each area)
communities are defined by:
taxonomic affinity
guild (specis that use the same resource)
functional group (species that function in similar ways eg nitrogen fixing plants)
The Theory of Island Biogeography
A method for asking how island area and isolation can act together to produce commonly observed species diversity patterns.
- Species richness S depends on the balance between immigration and extinction
- probabilities of immigration and extinction depend on the number of species already present and island characteristics such as size and isolation
- assumes: that all species are equivalent, making it a neutral model
Describe the extinction curve on the equilibrium model of biogeography island biogeography graph
1- When island S is small, life is easy, with few predators or competitors. The rate is therefore relatively low.
2- The larger the island S becomes, the more probable that resources will be used up efficiently. Thus many species that have established will experience a reduction in their density.
3- When island S is very high, any disturbance or resource-shortage is increasingly likely to wipe out the small, stressed populations present, so the rate rises to a high value
The extinction rate (or probability of extinction) is influenced by…
area.
Compared to some “average-sized” island at a given distance from the source area, the rates are expected to shift higher on small islands, but remain lower on large islands, leading to different Seq values.
Describe the immigration curve on the equilibrium model of biogeography island biogeography graph
1- When island S is small, nearly any successfully-establishing species will be a “new” one to the island- an immigrant. The rate is therefore relatively high.
2- The rate reduces because the source area contains only a limited number of species which have the capacity to reach the island- many of these will arrive and establish quickly, and once they have done so, they can no longer count as “new”
3- The more species reach the island, the fewer are left at the source -so “new” species run out, and the rate tails off to approach zero
The immigration rate is influenced mainly by
isolation distance. Compared to some “average-distance-from-source” island of a given size, the rates are expected to shift lower on hard-to-reach islands, but remain higher on more accessible islands, again leading to different Seq values.
neutral model
neutral models ignore species identity and focus on probabilistic processes of speciation, immigration and extinction
eg: Island biogeography theory (speciation is not important in the Island Biogeography theory
How does population size change through time
change in N = birth - death + Immigration - Emigration
How does species richness (S) change through time?
change in S = speciation -extinction + immigration
(speciation - extinction = diversification)
Biogeography
the study of patterns of species composition and diversity across geographic location
What ae some important patterns seen with taxa by the forest tour
- species richness and composition vary with latitude
- in general, lower latitudes have many more and different species than higher latitudes
- species richness and composition also vary by region of the world even at similar latitudes
What controls these large scale biogeographic patterns?
Wallace notes
- Land masses can be divided into six Biogeographic regions (corresponding roughly to earths tectonic plates)
- there is a gradient of species diversity with latitude
continental drift has resulted in unique flora nad fauna in some regions as time of isolation has given more time for evolutionary change and distinctive species
What drives the latitudinal diversity gradient?
There is still debate but most hypotheses fall into three categories:
-Diversification rate: the tropics have a higher rate of species diversification
- Diversification time: There has been more time form diversification in the tropics
- Productivity or carrying capacity: The tropics can support more species
Global scale patterns of species diversity and composition are the result of…
variation in speciation, extinction and dispersal at latitudinal and continental spatial scales and evolutionary time scales
Regional scale patterns of species diversity and composition are driven by and called
Gamma diversity, and are driven by dispersal across the landscape
Local and regional scales (landscape scale) are connected by___, which is ___ (___ diversity)
connected by turnover, which is the difference in species diversity and composition (beta diversity) from one community type to another across the landscape
Local scale patterns of species diversity and composition (___ diversity) are driven by,
(alpha diversity) is driven by physical conditions and species interactions
Intraspecific competition
a non-trophic interaction in which individuals of the same species are harmed by their shared use of a resource that limits their ability to grow, reproduce or survive
(leads to density-dependent population growth and sets K)
Interspecific competition
a non-trophic interaction in which individuals of different species are harmed by their shared use of a resource that limits their ability to grow reproduce or survive