Lecture 13: Species Diversity Flashcards
Define species diversity
The variety of organisms that make up a community
What are the two determining components of species diversity?
Species richness (# of species)- the number of different species in a community
Relative abundance (# of individuals in community)- the proportion each species represents of all individuals in a community
What do we use in order to compare diversity across communities?
The Shannon Diversity Index =
- (pA ln pA + pb ln pB + pc ln pC …)
[dont memorize]
3 birds 3 dogs 3 sheep 3 horses
25% 25% 25% 25%
H= -4(0.25 ln 0.25) = 1.39 Shannon Diversity
What is the importance of characterizing the species diversity of communities?
Diverse communities are more productive and stable and can withstand and recover from environmental stresses and invasive species.
What determines the species diversity of communities?
Area and Latitude
Define species-area curve
All other factors being equal a large geographic area has more species.
When looking at species richness by area, we notice that _____
As area increases, species richness increases
What are the area effects of islands? Big vs small islands, far from mainland to close to mainland?
Islands close to mainland have more species than one far. Small islands contain few species than do large islands.
Species richness on islands represents a balance between ____
Immigration of new species ad extinction of established species
What are immigration and extinction affected by on islands?
Affected by island size and distance from the mainland
What is the Island Equilibrium Model
As # of species increases, immigration decreases and extinction increases
- smaller islands have lower immigration and higher extinction rates
- islands close to the mainland have high immigration rates and low extinction rates
- equilibrium will be reached where rate of immigration is equal to rate of extinction
Species richness is __ in the tropics and _ towards the poles
Higher/greater, declining/lower
What are the two key factors affecting latitudinal gradients of species richness?
Two key factors are evolutionary history and climate
How has evolutionary history shaped the latitudinal diversity gradient?
Tropics as cradle (n)
- low extinction high speciation, great species richness as it is hotter
Tropics as museums (u)
- temperature goes up, more diversity, gets cold at poles less diversity more extinction
What are the two climatic factors correlated with biodiversity in terrestrial communities
Sunlight and precipitation
