Download Lecture3 biomes,dist web

Lecture 3:
Distributions and abundance
• Climates and Biomes
• Individual species distributions
–Invasive species
Climates and Biomes
• Global temp differences create wind
and drive atmospheric circulation
• formation of distinct temperature and
moisture “bands” from low to high
latitudes
• Results in distinctive plant assemblages
that are also formed in these distinct
zones = BIOMES
Climates and Biomes
•
Climate varies tremendously over globe
– abiotic factors such as rainfall and temperature
•
Enormous impact on plants and animals
and the resulting communities
Two big factors affect global climate:
1. Curvature of the earth -->temp gradient
2. Tilt of Earth axis --> Seasons
Biomes
• Major categories of world’s distinctive plant
assemblages
• Different biomes correlate well with climatic
factors
• Illustrate how organisms match their environments
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Biomes
Individual Distributions
• Tundra
– Very seasonal, very cold, very dry
• Taiga (Boreal Forest, N. Coniferous Forest)
• There are different scales of individuals
distributions:
– Highly seasonal, very vold, lots snow
• Temperate
– Geographic
– Regional
– Populations (habitat-related)
– Individual locations (e.g. territories)
– Seasonal, temperature fluctuates, rain+snow
– Grasslands & Forests
• Tropical
– HOT!, little seasonality, rainfall varies
– Savannas, Rainforests, and Deserts
• Deserts
– Hot & Dry, distributed throughout the world
Worldwide
Continental
Individual Distributions
• How do we study what factors determine the
distributions of organisms?
Cluster/
Population
Locality
Region
• Old way: Leibig’s law of the minimum
– Look where organisms are found and ask why
– Hypothesis: distribution of organism determined by
single environmental factor for which the organism
has narrowest range of control or adaptability
Individual
Locations
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Individual Distributions
• Leibig’s law of the minimum
– Use tolerance curves to determine which
environmental factors organism was
influenced by: GRAPH
– Problem: focuses on abiotic conditions
and the physiology of organisms but does
not consider potential effects of other
factors
– Realized vs. potential performance GRAPH!
Individual Distributions
• Factors that can limit species distributions:
– Abiotic env. conditions
• Temperature, water, nutrients, etc.
– Species Interactions
• predation, competition, disease, etc.
– Dispersal barrier
• Land or water barriers
– Behavior
• Habitat selection/preference
Individual Distributions
• Alternative way to Leibig:
– Look where organisms are NOT found and
ask why
– Hypothesis: distribution of organisms
determined by factors keeping them out of or
from being successful in other areas
Abiotic factors limiting distribution
Red Kangaroo Distribution and
Abundance - Australia
Number/km2
>20
10-20
5-10
1-5
0.1-1
<0.1
Distribution of Desert
Conditions - Australia
Deserts
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Abiotic factors limiting distribution
Barnacle Distributions and Climate - UK
Chthamalus sp. –
southern species
Balanus sp. – northern
Colder water
species
Species interactions & distributions
Red Kangaroo Abundance relative to a predator – Dingos
Dingos Absent
Dingos Present
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Kangaroo
Density
#/km2
12
8
4
Warmer water
30
20
10
10
20
30
Distance from Fence (km)
Habitat selection limiting distributions
Dispersal limiting distributions
Gypsy moth distribution before and after human-induced
introduction to the U.S.
Before introduction to U.S.
After introduction to U.S.
addition of shelter
C = control,
Kangaroo rat
E = experimental
addition)
Result: Kangaroo rat
prefers open areas,
pocket mice prefer
sheltered areas
Pocket mouse
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Distributions - CA examples
• California Salamanders
( Ensatina eschscholtzi spp.)
– Ring Species
• Monterey Pines (Pinus radiata)
• Likely have both biotic & abiotic constraints
Individual Distributions
• How do we determine which factors limit species
distributions?
• Can do transplant experiments or change
conditions to distinguish between different
factors
Dispersal?
Behavior?
Other organisms?
Abiotic factors?
“Natural Experiments”
• Introduced Species
– Overcome dispersal barrier
– Novel species interactions
– Different abiotic conditions
– -->Alters distribution dramatically!
• Examples
– Kudzu vine (Pueraria montana)
– Cane Toads! (Bufo marinus)
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