Lecture 14 diversity Flashcards
What is diversity (3)
Biological Diversity: variability among living organisms above, below, and at the species level
* Variation within species: genetic & population diversity
* Variation among species: local & regional diversity
Genetic diversity (2)
Higher genetic diversity leads to better resistance against environmental changes.
E.g. Caribou
– Different populations are adapted to the different extremes of their environment
– Large response diversity for the species
Population Diversity (3)
*Populations go extinct much faster than species
*Small range species go extinct faster
* Average of 220 populations per species
Landscape Diversity
differences of the various land uses and ecosystems within a larger area
Species diversity (2)
Species diversity: number, types, and distribution of organisms in a given area
Greater species diversity is linked to increased productivity and stability of an ecosystem
Species diversity math (3)
Local Diversity (α): Community
Regional Diversity (γ): Ecosystem
β Diversity (γ/ α): Species turnover or Habitat Diversity
Species diversity 2 key components
- Richness
- Evenness
Richness and evenness (2)
Species richness, is a count of the total number of different species in an area.
Evenness is How similar abundances of each species are to each other
Richness bias (3)
*There is always bias in our estimate of richness
*What is a species? There are so many definitions and none are always correct
*we often ignore small things or less prominent species
alpha, beta, and gamma diversity
Alpha diversity: Number of species found at a local scale
Gamma diversity: Number of species found at a regional scale
Beta diversity: measure of the difference in species composition (or turnover) between 2 or more habitats/local sites within a region
Why do larger areas have more species (4)
- Bigger areas are more likely to have a variety of different abiotic conditions
2.This diversity of abiotic conditions means there are a diversity of habitats - Those diverse habitats then support more/different species
- Bigger areas also support higher population sizes Larger populations are less likely to go extinct than smaller populations
Consequences for ecological interaction in the north (2)
- Low prey diversity promotes unstable population dynamics (cycles)
- Less species redundancy lower ecosystem resilience
Latitudinal gradient hypotheses (Null) (2)
Null: Species on the earth are randomly distributed. Because of this, most species are in /around the middle of the earth.
aka the mid-domain effect
think about it like this: if you had a bunch of different sized pencils in a box, some would be more to the left, some the right but most of the pencils would still reach to the center
Latitudinal gradient hypotheses (history)
The land on earth used to be much more central, and tropical. Since colder habitats are younger there is less time for speciation and adaptation compared to the highly diverse tropics
Latitudinal gradient hypotheses (spatial heterogeneity) (2)
*higher diversity in tropics due to increase in number of potential habitats
*lower environmental complexity moving away from equator
Latitudinal gradient hypotheses (competition)
Since the vast majority of death in the boreal region is due to abiotic factors, competition is not really at play. In the tropics there are no extreme weather conditions, so populations can increase density to the point where competition for resources is necessary = promotes species diversity through specialization
Latitudinal gradient hypotheses (predation)
increased species diversity in tropics is function of increased number of predators that regulate the
prey species at low densities . This decreases competition among prey species and allows coexistence of prey species and potential for new additions.
Gause’s law
two species competing for the same limiting resource cannot coexist. one will outcompete the other
Latitudinal gradient hypotheses (productivity)
tropics support a greater number of species because more resources are available, allowing for more specialization
* larger input of solar energy = more primary production
– in general: increase production = increase diversity
Latitudinal gradient hypotheses (Climate)
Tropic climates are much more constant, constant climate = finer specializations and adaptations, shallower niches
Latitudinal gradient hypotheses (disturbance)
if community disturbance frequency is very high = local extinction of species = lower species diversity
if community disturbance frequency is very low = competitive exclusion by dominant species = higher species diversity
diversity in the arctic (3)
The diversity of animal, plant and microbial species appears to be low in the Arctic
* decreases from the boreal forests to the polar deserts of the extreme North
* but primitive species are particularly abundant.