Transcript 19 Sp Div Regional to Globe

OBJECTIVES
• Species Diversity at scales above local
• Regional effects on local SD
• Equilibrium theory + Island Biog. Theory
• Regional SD
• Latitudinal SD
• Continental SD
• Global SD
What explains great variation in species
richness over the earth?
Figure 1
Multiple scales of species diversity
•
•
•
•
•
Local
Regional
Latitudinal
Continental
Global
Many factors influence regional and local
species richness.
Local diversity as f (regional diversity).
Figure 2
Comparing diversities of communities in
similar habitats in different regions can
reveal regional effects.
Figure 3
Saturation of local communities hypothesis:
test how local and regional diversity relate.
Figure 2
Figure 4
Variation in local species diversity
depends on regional diversity.
***Are these local
communities
saturated?
Figure 5
Equilibrium theories: diversity reflects a
balance between processes that add vs.
remove species.
• ***What processes add species?
•
speciation
•
immigration
• What processes subtract species?
•
extinction
•
emigration
• Differences in diversity between
communities reflect differences in relative
rates of these processes.
*** What is the pattern?
What two equilibrium factors may explain it?
Figure 6
Equilibrium theory of island biogeography:
# species = balance of immigration on a
regional scale vs. extinction on local scale.
Figure 7
Islands closer to the mainland support more
species because of higher immigration rates.
Figure 8
Larger islands support more species
because of lower extinction rates.
Figure 9
Which hypotheses are illustrated in
Figure (a) + (b)?
Figure 10
*** Do experimental results support ETIB?
Figure 11
Applications of Island Biogeography
Theory to:
• Terrestrial systems
•
mountain tops as islands
•
fragmented remnants as islands
• Design of nature reserves
Regional-scale patterns of diversity
also reflect:
• Habitat heterogeneity
• Suitability of physical conditions
• Isolation from centers of diversity
***What are three patterns in regional species
diversity? What factor accounts for each
pattern?
Figure 12
How do patterns of species richness differ
among taxa? Why?
Figure 13
***What are major changes among
regions from Tertiary to present? What
accounts for them?
What are major
differences today?
Figure 14
***Why did climate change during the Ice
Age contribute to Europe’s low species
richness?
Figure 15
Figure 15
What is relationship between tolerance of
low temperature / rainfall and extinction?
Figure 16
Multiple scales of species diversity
•
•
•
•
•
Local
Regional
Latitudinal
Continental
Global
***What is latitudinal gradient in woody
species diversity? What explains it?
Figure 17
Hypotheses to explain latitudinal gradient
in species diversity…
•
•
•
•
•
•
Time and stability
Heterogeneity in space and time
(Vegetation and food complexity)
Herbivore and pathogen pressure
Competition/niches
Disturbance
Multiple scales of species diversity
•
•
•
•
•
Local
Regional
Latitudinal
Continental
Global
How do history + biogeography + climate
change influence species diversity?
History of life is gauged by geologic time
scale.
Cretaceous 150mya
Cambrian 600mya -->
Permian 286mya
Equilibrium theory in continental communities:
balance between speciation and extinction on
regional scale
Figure 21
Has diversification been faster in tropics
than temperate area?
Figure 22
***Has diversity been constant? What is
role of extinction vs. additions?
Figure 18
Did species richness increase through time?
To what did richness correspond?
All species turned over during this time period.
Figure 19
Catastrophes --> what are
consequences - short- and long-term?
***Asteroid
impact-->
extinctions
of what?
Figure 20
Multiple scales of species diversity
•
•
•
•
•
Local
Regional
Latitudinal
Continental
Global
Continental drift --> positions of
continents change over geologic time.
Climate changes too --> influences
geography of evolution
Figure 23
Continental drift changed routes of
dispersal via separation + joining.
Figure 24
Wallace: Major zoogeographic regions
reflect long-term evolutionary isolation.
Figure 25
Exchanges of biotas after joining of
continents: e.g. The Panama land bridge
Figure 26
***How explain same body form in
multiple continents?
Convergence or
divergence?
Figure 27
Climate change influences distributions of
organisms. How does the historical extent
of climate zones help to explain global
patterns of
species richness?
Figure 28
Where does more diversification occur?
Why? How does this relate to more species
near 0 than at higher latitudes?
Figure 29
Climate change in N.A. shifted species
diversity; Miocene drier with grasslands.
Fig
Figure 30
Oak trees shifted their distributions after
end of most recent glacial period.
Figure 31
How does ‘dispersal limitation’ explain
differences in post-glacial expansion?
A,b = small; c,d = large seeded species
Figure 32
How does
climatic history
determine
species
distributions +
community
composition?
Figure 33