Download Limits to geographic distribution

Limits to geographic distribution
Lecture 3
Island fox
Review: Climate is the most fundamental
characteristic of the physical environment.
• Weather
– Present conditions—e.g. temperature, precipitation, humidity, cloud cover.
• Climate includes long‐term weather
– Averages – Extremes
– Variation
– Timing
Climate determines geographic distribution of organisms.
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Review: Latitudinal Differences in Solar Radiation at Earth’s Surface
• Sun rays perpendicular at equator vs spread over a large area at poles
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Atmospheric Circulation
• Differences in solar radiation across the surface of Earth cause winds and ocean current patterns.
• When solar radiation heats Earth’s surface, the surface warms and emits infrared radiation to the atmosphere, warming the air above it.
• Warm air is less dense than cool air, and it rises—uplift.
• Air pressure decreases with altitude, so the rising air expands, and cools.
• Cool air holds less water vapor than warm air.
• And, cold air is denser, so it sinks.
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Atmospheric Circulation
• Tropical regions receive the most solar radiation, and thus have the most precipitation.
• Uplift of air in the tropics results in a low atmospheric pressure zone.
• Air descends when it cools and forms a high pressure zone at about 30° N and S.
• Major deserts of the world are at these latitudes.
• high pressure zones with little precipitation form the “polar deserts”
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Atmospheric and Oceanic Circulation
• Water has a higher heat capacity than land—it can absorb and store more energy without changing temperature.
• Summer: Air over oceans is cooler and denser, so air subsides and high pressures develop over the oceans.
• Winter: Air over continents is cooler and denser, high pressure develops over continents.
• Land masses complicate ideal picture
– Seasonal pressure changes over ocean
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Figure 2.15 Annual Seasonal Temperature Variation (Ecology textbook)
Air temperatures on land show greater seasonal variation than those over the oceans.
• Coastal areas have a maritime climate: Little daily and seasonal variation in temperature, and high humidity.
• Areas in the center of large continents have continental climate: Much greater 7
variation in daily and seasonal temperatures.
Atmospheric and Oceanic Circulation
• Ocean currents affect climate.
– Gulf Stream affects the climate of Europe.
– Labrador (same latitude) is much cooler because of the cold Labrador Current.
– Labrador has boreal forest, Great Britain has deciduous 8
woodland and agriculture.
The Great Ocean Conveyor Belt
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Ocean surface waters are warmer and less saline than deep waters, and thus less dense. The layers don’t mix.
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The Great Ocean Conveyor Belt
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Ocean surface waters are warmer and less saline than deep waters, and thus less dense. The layers don’t mix.
Where warm tropical currents reach polar areas, the water cools, ice forms, and the water becomes more saline and more dense. The water mass sinks in these regions, and moves back toward the equator.
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Regional Climatic Influences
• Vegetation can also influence climate.
• Albedo—the capacity of a land surface to reflect solar radiation—is influenced by vegetation type, soils, and topography.
• For example, a coniferous forest has a darker color and lower albedo than bare soil or a dormant grassland.
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Regional Climatic Influences
• Evapotranspiration is the sum of water loss through transpiration by plants and evaporation from the soil.
• Evapotranspiration transfers energy (as latent heat) and water into the atmosphere, thereby affecting air temperature and moisture.
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Regional Climatic Influences
• Loss or alteration of vegetation can affect climate.
• Deforestation – increases the albedo of the land surface, lowering the absorption of solar radiation and resulting in less heating.
– less cooling by evapotranspiration, due to loss of leaf area.
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Regional Climatic Influences
• Decreased evapotranspiration results in less moisture in the atmosphere and less precipitation.
• Deforestation in the tropics can lead to warmer, dryer regional climate.
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Global Climatic Patterns
Large-scale atmospheric and oceanic
circulation patterns establish global patterns
of temperature and precipitation.
• Average annual temperatures become progressively cooler away from the equator toward the poles, but the patterns are influenced by ocean currents and relative distribution of land masses.
• Regional features (distribution of land and water, elevation, topography, and vegetation) influence regional climatic patterns set by solar radiation
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Review: our water world
• 97% of water on the planet is salty
• Freshwater is – Scarce (mostly locked up in glaciers, snow, very deep groundwater)
– Unevenly distributed
– important for biodiversity (and humans)
• Per capita usable freshwater will ↓ with ↑population, climate change, and contamination
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Figure 3.14 Spatial Zonation of a Stream
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Figure 3.13 Stream Orders
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Freshwater Biological Zones
• The river continuum concept describes the compositional changes of biological communities with stream order and channel size (Vannote et al. 1980).
• As streams increase in size, detrital input from riparian vegetation decreases and the importance of this as a food source decreases.
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http://www.lakeaccess.org/ecology/lakeecologyprim9.html
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Review: Marine system
• kelp ecosystems grow rapidly
– 30 cm/day in SoCA
• coral ecosystems grow slowly
– 0.8‐80 mm/yr
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Review: details of ocean circulation and upwelling • Coriolis effect
• Ekman transport
Is this Ekman spiral model in the northern hemisphere or the southern hemisphere?
NORTHERN
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Review: details of ocean circulation and upwelling • upwelling
• Ocean circulation
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Review: ecological effects of upwelling • Cold nutrient‐
rich waters 
seaweed and phytoplankton  higher trophic levels (fish, inverts)
• Strength varies (ex. Pt Conception)
Upwelling regions=1% of ocean surface & 50% of global fish landings!
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http://oceanexplorer.noaa.gov/
Review: east coast vs west coast
• River outflow from US east coast supplies most nutrients to coastal ecosystems (Hickey and Banas 2003) versus
• Wind‐driven upwelling on the US west coast (continental shelf is narrow here which allows very cold, deep water to rise during upwelling events)
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Outline: Limits to geographic distribution
• Dispersal often limits ranges on a global scale
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Types of dispersal
Aquatic invasions
Tree recolonization at the end of the ice age
Island colonization
• Physical or chemical factors usually limit ranges on regional and continental scales
– Range extension via adaptation
– Impacts of rapid climate change
• Predators, diseases, parasites and competition can limit ranges on a local scale
– Limitation by predators
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Dispersal often limits ranges on a global scale
• What are the two main types of dispersal?
– Diffusion—gradual spread
– Jump dispersal—rapid spread over large distances
• Anthropogenic vectors
• Birds • Rafting floating algal mats
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European green crab
Genetic evidence of two separate invasions Relative frequencies of green crab haplotypes (combination of DNA sequences, or alleles)
(Roman 2006)
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Dispersal vectors of Green Crab
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What could have potentially prevented this?
Zebra mussel invasion into Great Lakes and beyond
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Ballast water exchange
Zebra mussel invasion into Great Lakes and beyond
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Outline: Limits to geographic distribution
• Dispersal often limits ranges on a global scale
–
–
–
–
Types of dispersal
Aquatic invasions
Tree recolonization at the end of the ice age
Island colonization
• Physical or chemical factors usually limit ranges on regional and continental scales
– Range extension via adaptation
– Impacts of rapid climate change
• Predators, diseases, parasites and competition can limit ranges on a local scale
– Limitation by predators
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Tree recolonization
• Reid’s paradox—discrepancy between observed and expected
range expansion based on average seed dispersal distances at the end of the ice age
(diffusion predicts 36 km expansion since ice age but actual is 1000 km!)
1. Migration depends on extreme events not average events (wind or animals can bring seeds further)
2. Some trees may have survived in isolated pockets during ice age (but no fossil record of this)
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Island colonization
• New Guinea as a mainland to a number of smaller islands (world’s 2nd largest island after Greenland!)
• (More on Theory of Island Biogeography‐Ch. 14)
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Outline: Limits to geographic distribution
• Dispersal often limits ranges on a global scale
–
–
–
–
Types of dispersal
Aquatic invasions
Tree recolonization at the end of the ice age
Island colonization
• Physical or chemical factors usually limit ranges on regional and continental scales
– Range extension via adaptation
– Impacts of rapid climate change
• Predators, diseases, parasites and competition can limit ranges on a local scale
– Limitation by predators
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Do physical or chemical factors limit a range?
1. Which life stage is most vulnerable?
2. What is the physiological tolerance at that stage?
3. Does the factor vary more than the organism can tolerate outside of its range?
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Zonation in the intertidal zone
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Joseph Connell
• Professor Emeritus, Department of Ecology, Evolution and Marine Biology, UCSB
• pioneered field ecological experiments, intertidal habitats in Scotland 1950‐70’s
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Semibalanus (formerly Balanus)
Chthamalus
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Thais Lapillus
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How would you design an experiment to see what factors influence the distribution of barnacle species?
plates
cages
Thais Lapillus
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Connell followed the survival % of newly settled (from their planktonic larval stage) Chthamalus over a 2 year period Upper intertidal zone
Survival of Chthamalus (%)
Survival of Chthamalus (%)
Middle intertidal zone
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Under what conditions was Chthamalus survival highest?
And why?
Upper intertidal zone
Survival of Chthamalus (%)
Survival of Chthamalus (%)
Middle intertidal zone
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Under what conditions was Chthamalus survival highest?
And why?
wetter
Upper intertidal zone
Survival of Chthamalus (%)
Survival of Chthamalus (%)
Middle intertidal zone
The relative effects of competition can be dependent on the physical (abiotic) environment!
No competition
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What hypothesis is supported by the results of this research?
A. In the intertidal ‐ Abiotic factors tend to limit the upper distribution of organisms, while biotic factors tend to limit the lower distribution of organisms. B. In the intertidal ‐ Biotic factors tend to limit the upper distribution of organisms, while abiotic factors tend to limit the lower distribution of organisms. 47
Quick overview of tidal cycles
The gravitational pull (tidal force) of the moon and sun in line result in more extreme tides than when not in line.
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http://www.windows2universe.org/earth/Water/ocean_tides.html&edu=elem
MHWS=mean high water spring; MHWN=mean high water neap; 49
MTL=mean tide level; MLWN=mean high water neap; MHWS=mean high water spring; Outline: Limits to geographic distribution
• Dispersal often limits ranges on a global scale
–
–
–
–
Types of dispersal
Aquatic invasions
Tree recolonization at the end of the ice age
Island colonization
• Physical or chemical factors usually limit ranges on regional and continental scales
– Range extension via adaptation
– Impacts of rapid climate change
• Predators, diseases, parasites and competition can limit ranges on a local scale
– Limitation by predators
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Range extension via adaptation
• 1920’s and 30’s: Turesson’s common garden experiments to determine how much species geographic differences were due to environment (phenotypic variation) vs genes
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Variation Within Species
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Sapphire rockcress Arabis fecunda
– Rare, perennial herb found in calcareous soil outcrops in western Montana
– 19 populations separated into two groups (‘high elevation’ and ‘low elevation’)
Rain in western Montana
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Variation Within Species
The flowers taken from low
elevation sites (where it
rains less) used water more
efficiently than the flowers
from high elevation sites
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McKay et al. 2001
Ecotypes (term coined by Turesson)
• genetically distinct group within a species due to adaptation
Littorina subrotundata, as found on
barnacles
Littorina subrotundata, as found in
marsh area
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Dispersal influences variation
within species
Littorina saxatilis Photo by Olivier Caro
lower dispersal ability  greater diversity…
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Dispersal influences variation within species… ex: two littorinids with the same range
Littorina littorea larval stage lasts 4‐6 weekspopulations tend to be more homogenous across space
L. saxatilis are direct developers (no larval stage)gene flow across space is more restricted encouraging local adaptation
Micro‐environmental and community differences will influence adaptation within a species on a small scale leading to greater genetic variation across the entire range of the species
lower dispersal ability  greater diversity…why?56
Outline: Limits to geographic distribution
• Dispersal often limits ranges on a global scale
–
–
–
–
Types of dispersal
Aquatic invasions
Tree recolonization at the end of the ice age
Island colonization
• Physical or chemical factors usually limit ranges on regional and continental scales
– Range extension via adaptation
– Impacts of rapid climate change
• Predators, diseases, parasites and competition can limit ranges on a local scale
– Limitation by predators
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Predicted changes in precipitation patterns caused by global warming 58
?
Even if we curtail emissions now, we have already “committed” to a certain amount of impact from 59
current and past emissions
Other models… other predictions
• NOAA Earth System Research Laboratory (ESRL) predict reduced precipitation across the Southwest
• Combining 18 global climate models (and the moderate A1B emissions scenario from the IPCC report)
www.southwestclimatechange.org/node/790
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American Beech
• Current geographic range and predicted future range for American beech under two climatic‐change scenarios • Since last ice age, beech has migrated north at a rate of 0.2 km/year
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Changes in Phenology (study of periodic plant and animal life cycle events)
(McCarty 2001)
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What can limit ranges on a local scale?
• Physical‐chemical environment – (e.g., temp, desiccation)
• Biological environment
– predators
– competition (more on this next week)
– diseases, parasites (more on this next week with our Guest Lecture)
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Soliders displaying Wolf pelt at Soda Butte Creek patrol station, Yellowstone National Park, 1905
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An example of predator control
• 1872 Yellowstone National Park created with no legal protection for wildlife
• 1883 prohibition of hunting most park animals except for wolves, coyotes, bears, mountain lions and other small predators
• 1907 predator control programs began “Animal Damage Control”—in this year 1800 wolves and 23,000 coyotes killed in 39 U.S. National Forests
• 1926 gray wolves extirpated from Yellowstone
• 1967 listed as endangered
• 1978 National Park Service wildlife biologist John Weaver recommends reintroduction
• 1980’s wolves begin to recolonize from Canada into the US
• 1995 first release of wolves into Yellowstone
• 2003 gray wolves downlisted from endangered to 65
threatened status
Ecological effects of predator control and reintroduction
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Without wolves what do you think happened to Elk and Aspen populations? (~92% of the winter diet of Yellowstone wolves is elk; ~ 22 ungulates per wolf annually)
Although wolves consume beavers, the reintroduction of wolves have had a positive effect on beaver populations. Why might this be happening?
Lower pressure on willow from elk, allows more willow to be available to beavers—important resource during the winter; in other words fewer elks means reduced competition with beavers for willow
The “top‐down effect” of top predators on other animals and plants in the food web is an example of a trophic cascade.
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Outline: Limits to geographic distribution
•
•
•
Dispersal often limits ranges on a global scale
– Types of dispersal
– Aquatic invasions
– Tree recolonization at the end of the ice age
– Island colonization
Physical or chemical factors usually limit ranges on regional and continental scales
– Intertidal example: Physical factors set upper limits (temp, desiccation), biotic factors set lower limits (competition, predation)
– Range extension via adaptation
– Dispersal influences variation within species
– Impacts of rapid climate change
Predators, diseases, parasites and competition can limit ranges on a local scale
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– More details in later lectures