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Climate Effects on Species
Concept 52.4: Interactions between
organisms and the environment limit
the distribution of species
• Species distributions are the result of ecological
and evolutionary interactions through time
• Ecological time is the minute-to-minute time
frame of interactions between organisms and
the environment
• Evolutionary time spans many generations and
captures adaptation through natural selection
• Events in ecological time can lead to evolution
• For example, Galápagos finches with larger
breaks were more likely to survive a drought
as they could eat the available larger seeds
• As a result, the average beak size was larger in
the next generation
• This resulted in an evolutionary change
• Both biotic and abiotic factors influence
species distribution
– For example, temperature, water availability, and
interspecific interactions, affect the distribution of
the saguaro cacti
Figure 52.15
ARIZONA
CALIFORNIA
BAJA
CALIFORNIA
SONORA
BAJA
CALIFORNIA
SUR
GULF
OF
CALIFORNIA
N
100 km
Sonoran desert
Saguaro cacti observed
Figure 52.15a
• Ecologists ask questions about where species
occur and why species occur where they do
Figure 52.16-1
Why is species
X absent
from an area?
Does dispersal
limit its
distribution?
Figure 52.16-2
Why is species
X absent
from an area?
Yes
Does dispersal
limit its
distribution?
No
Area inaccessible
or insufficient time
Does behavior
limit its
distribution?
Figure 52.16-3
Why is species
X absent
from an area?
Yes
Does dispersal
limit its
distribution?
No
Area inaccessible
or insufficient time
Does behavior
limit its
distribution?
Yes
No
Habitat selection
Do biotic factors
(other species)
limit its
distribution?
Figure 52.16-4
Why is species
X absent
from an area?
Yes
Does dispersal
limit its
distribution?
No
Area inaccessible
or insufficient time
Does behavior
limit its
distribution?
Yes
No
Habitat selection
Do biotic factors
(other species)
limit its
distribution?
Yes
No
Predation,
parasitism,
competition,
disease
Do abiotic factors
limit its
distribution?
Figure 52.16-5
Why is species
X absent
from an area?
Yes
Does dispersal
limit its
distribution?
No
Area inaccessible
or insufficient time
Does behavior
limit its
distribution?
Yes
Habitat selection
No
Do biotic factors
(other species)
limit its
distribution?
Yes
No
Water, Oxygen, Salinity,
pH, Soil nutrients, etc.
Temperature, Light,
Soil structure, Fire,
Moisture, etc.
Chemical
factors
Physical
factors
Predation,
parasitism,
competition,
disease
Do abiotic factors
limit its
distribution?
Dispersal and Distribution
• Dispersal is the movement of individuals or
gametes away from centers of high population
density or from their area of origin
• Dispersal contributes to the global distribution
of organisms
Natural Range Expansions and
Adaptive Radiation
• Natural range expansions show the influence
of dispersal on distribution
– For example, cattle egrets arrived in the Americas
in the late 1800s and have expanded their
distribution
• In rare cases, long-distance dispersal can lead
to adaptive radiation
– For example, Hawaiian silverswords are a diverse
group descended from an ancestral North
American tarweed
Figure 52.17
Current
1970
1966
1965
1960
1961
1958
1943
1951
1956
1970
1937
Figure 52.17a
Species Transplants
• Species transplants include organisms that are
intentionally or accidentally relocated from their
original distribution
• If a transplant is successful, it indicates that its
potential range is larger than its actual range
• Species transplants can disrupt the communities or
ecosystems to which they have been introduced
Behavior and Habitat Selection
• Some organisms do not occupy all of their
potential range
• Species distribution may be limited by habitat
selection behavior
Biotic Factors
• Biotic factors that affect the distribution of
organisms may include
– Predation
– Herbivory
• For example, sea urchins can limit the distribution of
seaweeds
– Competition
– Mutualism
– Parasitism
Figure 52.18
Sea urchin
Limpet
Seaweed cover (%)
100
80
Both limpets
and urchins
removed
60
Only urchins
removed
40
Only limpets removed
20
0
August
1982
Control (both urchins
and limpets present)
February
1983
August
1983
February
1984
Figure 52.18a
Sea urchin
Figure 52.18b
Limpet
Abiotic Factors
• Abiotic factors affecting the distribution of
organisms include
– Temperature
– Water
– Oxygen
– Salinity
– Sunlight
– Soil
• Most abiotic factors vary in space and time
Temperature
• Environmental temperature is an important factor in
the distribution of organisms because of its effects
on biological processes
• Cells may freeze and rupture below 0°C, while most
proteins denature above 45°C
• Mammals and birds expend energy to regulate their
internal temperature
Water and Oxygen
• Water availability in habitats is another
important factor in species distribution
• Desert organisms exhibit adaptations for
water conservation
• Water affects oxygen availability as oxygen
diffuses slowly in water
• Oxygen concentrations can be low in deep
oceans and deep lakes
Salinity
• Salt concentration affects the water balance of
organisms through osmosis
• Most aquatic organisms are restricted to either
freshwater or saltwater habitats
• Few terrestrial organisms are adapted to high-salinity
habitats
• Salmon are able to migrate between freshwater and
ocean
Sunlight
• Light intensity and quality (wavelength) affect
photosynthesis
• Shading by leaves makes competition for light
intense on the forest floor
• Water absorbs light; as a result, in aquatic
environments most photosynthesis occurs near
the surface
• In deserts, high light levels increase temperature
and can stress plants and animals
Figure 52.19
Rocks and Soil
• Many characteristics of soil limit the
distribution of plants and thus the animals
that feed on them
– Physical structure
– pH
– Mineral composition
Figure 52.UN03a
Data from the Field Experiment
Average Biomass (g/100 cm2)
Spartina patens
Typha angustifolia
Salt
Marshes
Freshwater
Marshes
Salt
Marshes
Freshwater
Marshes
With
neighbors
8
3
0
18
Without
neighbors
10
20
0
33
Figure 52.UN03b
Data from the Greenhouse Experiment
0
20
40
60
80
100
% maximum biomass
(Spartina patens)
77
40
29
17
9
0
% maximum biomass
(Typha angustifolia)
80
20
10
0
0
0
Salinity (parts per
thousand
Figure 52.UN03c
Spartina patens
Figure 52.UN03d
Typha angustifolia
Figure 52.UN04
Does dispersal limit its distribution?
Yes
Area inaccessible or
insufficient time
No
Does behavior limit its distribution?
Yes
Habitat selection
No
Do biotic factors (other species)
limit its distribution?
No
Do abiotic factors limit
its distribution?
Yes
Predation, parasitism,
competition, disease
Chemical factors:
Water, oxygen, salinity,
pH, soil nutrients, etc.
Physical factors:
Temperature, light,
soil structure, fire,
moisture, etc.
Figure 52.UN05
Altitude (m) Mean height (cm)
Figure 52.UN06
75
50
25
0
3,000
2,000
Sierra Nevada
1,000
0
Seed collection sites
Great Basin
Plateau
Figure 52.UN07