Lecture 16 Flashcards
1
Q
Biogeography
A
- the study of patterns of species composition and diversity across geographic locations
Ex. The Amazon rainforest is the most species-rich forest in the world – with approximately 1,300 tree species
2
Q
Lower Latitudes
A
- closer to the equator
- Have many more and a wider variety of species than higher latitudes
3
Q
Species Richness and Composition
A
- vary from continent to continent
- same community type or biome can vary in species richness and composition depending on its location on Earth
4
Q
Spatial Scales
A
- Interconnected in a hierarchical way
- Patterns of species diversity and composition at one spatial scale setting the conditions for patterns at smaller spatial scales
- Not the same for all organisms
5
Q
Global Scale
A
- the entire world
- Species have been isolated from one another on different continents or in different oceans by long distances and over long periods
- Rates of speciation, extinction and dispersal help determine differences in species diversity and composition
6
Q
Regional Scale
A
- areas with uniform climate
- species are bound by dispersal to that region
7
Q
Regional Species Pool
A
- all the species contained within a region
- Gamma diversity (whole region)
- Provides raw material for local assemblages and sets the theoretical upper limit on species diversity for communities
8
Q
Landscape
A
- topographic and environmental features of a region
9
Q
Species Composition and Diversity Vary Depending On
A
- how the landscape shapes rates of migration and extinction
10
Q
Local Scale
A
- equivalent to a community
- Species physiology and interactions with other species are important factors in species diversity
- alpha diversity
11
Q
Beta Diversity
A
- Change in species number and composition, or turnover of species, from one community type to another
- Connects local and regional scales
- How different one community is from another
12
Q
Global Biogeography
A
- Global patterns of species diversity and composition are controlled by geographic area and isolation, evolutionary history, and global climate change
13
Q
Alfred Russel Wallace
A
- 1923-1913
- Father of biogeography
- Main contribution: was the study of species distributions across large spatial scales
14
Q
Overlaid species distributions and geographic regions and revealed two global patterns
A
1) there is a gradient of species diversity with latitude
2) Earth’s land mass can be divided into six biogeographic regions
- Six biogeographic regions correspond roughly to Earth’s six major tectonic plates
15
Q
Continental Drift
A
- Can be found in the fossil record and in existing taxonomic groups
16
Q
Pangaea/ Permian Period
A
- 251 million years ago
- one massive continent
17
Q
Cretaceous Period
A
- 100 million years ago
- 2 supercontinents- Laurasia, Gondwana
18
Q
Early Tertiary Period
A
- 60 million years ago
19
Q
Vicariance
A
- evolutionary separation of species by barriers such as those formed by continental drift
20
Q
Most Oceans Have _____
A
- low nutrient availibility
21
Q
Global Patterns of Species Richness
A
- If we assume dispersal rates are similar everywhere, then species richness should reflect a balance between extinction and speciation
22
Q
Species Diversification
A
- Speciation rate - extinction rate = species diversification
- net increase/ decrease of species over time
- should be controlled by speciation, extinction, and dispersal
23
Q
Species Diversification Rate
A
- Tropics have the most land area on Earth and temperatures are very stable
- Large thermally stable areas should decrease extinction rates:
- Speciation by geographic isolation would be more likely
24
Q
Species Diversification Time
A
- Tropics are thought to have been more climatically stable over time
- Species have had more time to evolve
- Temperate and polar regions have undergone severe climatic changes:
Glaciation
Disrupting species
Diversification - Most species originate in the tropics and then move to other regions during warm climatic periods
25
Productivity or Carrying Capacity
- Highest in the tropics (terrestrial)
- High productivity promotes large population sizes due to carrying capacity being larger
- Higher productivity leads to lower extinction rates
- Greater coexistence
- Overall higher species richness
- Some very productive habitats have low species diversity
Ex; estuaries
26
The Tropics
- Have the most land area
- The southern hemisphere has more oceans than the northern hemisphere
- Can be seen as a “cradle” of diversity
- Can also be a “museum” – species that diversify there tend to stay there
- Loss of biodiversity could cut off the supply of new species to higher latitudes in the future
- Species diversity peaks during ‘icehouse’ conditions
27
Regional Biogeography
- regional differences in species diversity are influenced by area and distance, which determine the balance between immigration and extinction rates
28
Species-area Relationship
- species richness increases with the area sampled
- an important concept in regional biogeography
29
Species Area Curves
- Plot species richness (S) of a sample against area (A) of the sample
- Relationship between S and A is estimated by linear regression:
- S = zA + c
z = slope
c = y-intercept
- Species area data not usually linear
- S and A are transformed into logarithmic values to obtain a straight line
30
Islands
- all display the same basic pattern
- Large islands have more species than small islands
- Can be any kind of isolated area surrounded by dissimilar habitats (matrix habitat)
Ex. Habitat fragments such as in the Amazon rainforest, can be considered islands
31
Island Species Diversity
- shows a strong negative relationship to distance from a source of species
- Island size and degree of geographic isolation are always confounded
32
Equilibrium Theory of Island Biogeography
- Developed by MacArthur and Wilson
- The number of species on an island depends on a balance between immigration or dispersal rates and extinction rates
33
Simberloff and Wilson
- 1969
- Manipulated mangrove islands in Florida by spraying with insecticides to remove all insects and spiders
34
The Largest Ecological Experiment on Earth
- The number of fish species in the Amazon River exceeds the total number found in the entire Atlantic Ocean
- One hectare of rainforest in the Amazon contains more plant species than all of Europe!
35
Edge Effects
- Large Habitat fragmentation created
- The transition between forest matrix habitat
Ex; trees at the edge are exposed to more light, higher temperatures, wind, fire, and diseases
- Can contribute to local extinctions
36
In the Southern Amazon
- Burning is used regularly, and keeps the forest edges in a constant state of disturbance
- Fire-tolerant species increase and edge effects extend into the fragment, reducing its effective size
