Diversity and Abundance Flashcards
Machia Seal Island
tons of different types of warblers landed here because they were exhausted from migration and the diversity was insane
Species abundance curve
- most species are moderately abundant
- very few are super rare or super common
Relative abundance
- proportion each species represents of all individuals in the community
- consistent between habitats and taxonomic groups
Species diversity (definition and parts)
- variety of organisms that make up a community
- determined by species richness and relative abundance
species richness
of different species in a community
What happens to diversity if your sample size is too small? What happens to diversity when you increase the sample size area?
- you underrepresent rare species and overrepresent common ones
- you find more species so diversity goes up
Shannon-Weaver Index
H = sum of pilnpi
where pi is the relative abundance
Abundance
how many individuals of a certain species
density
number of individuals per unit area
Relationship between nutrients and plant/algae diversity
- negative relationship
- reduces number of limiting nutrients
- causes competitive exclusion
Soons et al. experiments
- adding nitrogen reduced plant richness by 16%
- adding phosphorus did nothing
Two major biogeographical factors that affect species diversity
- lattitude (tropics are more diverse than poles)
- area (bigger area means more diversity)
Tree species per hactre
- Michigan = 10-15
- S.E. U.S. = 30
- Tropical Peru = 300
hot spots
- very diverse due to high number of endemic species
- Tropical areas near equator
- islands
- Mediterranean ecosystems
Why does latitude affect diversity (weather)
- dif latitudes have dif levels of sunlight and precipitation
- higher levels of evapotranspiration = more diversity
evapotranspiration
- evaporation of water from soil plus the transpiration of water from plants
- potential evaoptranspiration = potential water loss, assuming the presence of water
Why does latitude affect diversity (time)
- Tropical areas have had more time for speciation to occur (also more extinction)
- polar regions have had to restart due to glaciation
What kind of environments are good for diversity and how do phytoplankton/algae/diatoms reject this?
- complex environments = high diversity
- algae can live in simple communities if they have different trophic niches and have different ratios of nutritional needs
open ocean hot spots
- usually close to land
- only kinda follow the equator rule
What forms of life contribute the most to diversity?
-arthropods (especially insects)
-flowering plants
(prokaryote diversity is mostly unknown)
Biogeography
the study of the geographical distribution of species
- provides evidence for evolution
- an understanding of continental movement and modern species helps us know when and where these species evolved
Species Area Effect
- all other factors being equal, bigger area = more species
- S = cA^z
- S = # of species
- c = constant
- A = area
- z = how many species should be found as area increases
-in log-log plot of S vs A, z is the slope of the line through the data
Island equilibrium model
- richness = balance of immigration and extinction
- more S = less I + more E
- less A = less I + more E
- close to land = more I + less E
Wilson and Simberlof experiment
- Tested diversity of mangrove tree islands in Florida keys
- counted species
- fumigated island
- tracked increase of species over time
- equilibrium number returns to normal
Clements climax community
-thought that most communities were in a state of equilibrium and were governed by cliamate
Nonequilibrium model
- describes commuities as constantly changing after disturbance
- ex: Yellowstone forest (fire)
Intermediate disturbance hypothesis
- low and high levels of disturbance reduce diversity
- medium disturbance increases diversity
- high disturbance excludes slow-growing species
- low disturbance allows dominant species to exclude less competitive ones
Examples of intermediate disturbance hypothesis
- Townsend stream experiment
- diversity on boulders in intertidal zone
- prairie dogs open areas for colonization
Primary production and species richness
- PP increases with more species
- grazers increase PP (serangetti)
- increased growth rate due to low biomass (from being eater=n), don’t need to self-shade, and smaller leaf size
Disturbance
-event that changes community, removes organisms, and alters resource availability
