LB

Ecology Lecture Notes

Intro to Ecology 2

LG: Distribution and Abundance of Species

  • What explains the distribution and abundance of species?

Major Drivers of Weather/Climate

  • Sunlight Angle and Intensity:
    • North Pole: Low angle of incoming sunlight, small amount of sunlight per unit area.
    • Moderate Latitudes: Moderate angle of incoming sunlight.
    • Equator: Sunlight directly overhead, large amount of sunlight per unit area.

Global Air Circulation

  • Hadley Cells:
    • Circulation between 30°N and 30°S latitude.
  • Ferrel Cells:
    • Air circulation cells in mid-latitudes.
  • Polar Cells:
    • Air circulation cells near the poles.
  • Features:
    • Subpolar low
    • Polar high
    • Polar easterlies
    • Polar front
    • Subtropical high (Horse latitudes)
    • Westerlies
    • NE and SE trade winds
    • Equatorial low (Doldrums)

Global Wind Patterns

  • General Patterns:
    • Polar Easterlies.
    • Westerlies.
    • Trade Winds (Northeast and Southeast).
  • Ocean Currents:
    • North Pacific Gyre, South Pacific Gyre, Atlantic Gyre, Indian Ocean Gyre.
    • California Current, North Equatorial Current, South Equatorial Current, West Wind Drift, East Wind Drift, Kuroshio Current, Australian Current, Benguela Current, etc.
    • Warm and cold currents are indicated on the map.

Seasonal Shift of Cells

  • June:
    • Sun overhead at the Tropic of Cancer (23°N).
    • The cells shift northwards as the heat equator is in the northern hemisphere.
  • December:
    • Sun overhead at the Tropic of Capricorn (23°S).
    • The cells shift southwards as the heat equator is in the southern hemisphere.

Regional Effects

  • Rain Shadows:
    • Air rises over mountains and cools, causing rain.
    • Example: Cascade Mountains.
      • West side: Moisture-laden air from the Pacific Ocean.
      • East side: Dry air creates desert conditions.

Biomes

  • Major groupings of plant and animal communities, defined by dominant vegetation type.
  • Most important variables:
    • Temperature.
    • Water availability.

Biome Distribution Factors

  • Temperature and Precipitation:
    • Annual precipitation (cm) vs. Average temperature (°C) determine biome type.
    • Examples:
      • Tropical rain forest: High precipitation and temperature.
      • Temperate seasonal forest: Moderate precipitation and temperature.
      • Boreal forest: Low temperature, moderate precipitation.
      • Tundra: Very low temperature, low precipitation.
      • Subtropical desert: High temperature, very low precipitation.
  • Rule of Thumb:
    • 20 mm of monthly precipitation for each 10°C in temperature provides sufficient moisture for plant growth.
    • When the precipitation line is above the temperature line on a graph, plant growth is supported.

Climate and Biome Examples

  • Boreal Forest:
    • Location: Whitehorse, Canada.
    • Climate: Boreal (VIII).
    • Elevation: 703 meters.
    • Annual precipitation: 267 mm.
    • Average temperature: -0.7 °C.
  • Temperate Seasonal Forest:
    • Location: Omaha, Nebraska.
    • Climate: Nemoral (VI).
    • Elevation: 337 meters.
    • Annual precipitation: 700 mm.
    • Average temperature: 10.8 °C.

Additional Biome Examples

  • Tundra:
    • Location: Baker Lake, Canada.
    • Climate: Polar (IX).
    • Elevation: 4 meters.
    • Annual precipitation: 208 mm.
    • Average temperature: -11.9 °C.
  • Temperate Grassland/Desert:
    • Location: Salt Lake City, Utah.
    • Climate: Continental (cold deserts) (VII).
    • Elevation: 1,329 meters.
    • Annual precipitation: 339 mm.
    • Average temperature: 11.0 °C.
  • Subtropical Desert:
    • Location: Chiclayo, Peru.
    • Climate: Subtropical (hot deserts) (III).
    • Elevation: 31 meters.
    • Annual precipitation: 31 mm.
    • Average temperature: 21.9 °C.
  • Tropical Rain Forest:
    • Location: Andagoya, Colombia.
    • Climate: Equatorial (I).
    • Elevation: 65 meters.
    • Annual precipitation: 6,905 mm.
    • Average temperature: 27.2 °C.

Terrestrial Biomes

  • Ice sheet and polar desert
  • Tundra
  • Taiga (Boreal Forest)
  • Temperate Broadleaf Forest
  • Temperate Steppe
  • Subtropical Rainforest
  • Mediterranean Vegetation
  • Monsoon Forest
  • Desert
  • Xeric Shrubland
  • Dry Steppe
  • Semiarid Desert
  • Grass Savanna
  • Tree Savanna
  • Subtropical Dry Forest
  • Tropical Rainforest
  • Alpine Tundra
  • Montane Forests

Anthropogenic Biomes

  • Biomes significantly altered by human activities.
    • Examples: Dense Settlements, Urban, Cropped & Pastoral, Pastoral Villages, Rainfed Villages, Rainfed Mosaic Villages, Irrigated Cropland, etc.
  • Wildlands: Natural, Semi-natural.
  • Inhabited: Residential, Villages, Rangeland, Cropland, Forested.
    *Reference: Ellis, E. C., and N. Ramankutty (2008). Putting people in the map: anthropogenic biomes of the world. Frontiers in Ecology and the Environment, vol. 6. doi: 10.1890/070062.

Aquatic Biomes

  • Fresh and salt water (salinity).
  • Key Physical Factors:
    1. Nutrient availability.
    2. Water depth.
    3. Water movement.
  • Light Penetration:
    • Red wavelengths are not available underwater.
    • Blue wavelengths dominate underwater.
    • Many organisms require wavelengths of about 680 nm for peak photosynthetic efficiency.

Lakes

  • Zones:
    • Photic zone: light for photosynthesis
    • Aphotic zone: little or no light
  • Stratification and Turnover:
    1. Winter: Dense 4°C water at the bottom becomes nutrient-rich. Surface becomes oxygenated.
    2. Spring turnover: Surface water warms to 4°C and sinks, carrying O_2 down and driving nutrients up.
    3. Summer: Dense 4°C water at the bottom becomes nutrient-rich. Surface becomes oxygenated.
    4. Fall turnover: Surface water cools to 4°C and sinks, carrying O_2 down and driving nutrients up.

Oceans

  • Zones:
    • Photic zone
    • Aphotic zone
    • Continental shelf
  • Upwelling:
    1. Winds blow along the coast, moving surface water.
    2. Surface water is forced offshore due to Earth's rotation.
    3. Nutrient-laden water wells up from the bottom to replace the surface water.

Population Ecology I

  • Why does it matter?
    • Conservation biology
    • Invasive species management
    • …

Range

  • Global Range: entire distribution of a species.
  • Regional Range: distribution within a specific area.
  • Local Range: distribution within a small area.

Population Size

  • Factors Determining Population Size:
    • Births: Add individuals to a population.
    • Deaths: Remove individuals from a population.
    • Immigration: Add individuals to a population.
    • Emigration: Remove individuals from a population.

Life Table for Lacerta vivipara (Females in the Netherlands)

  • Variables:
    • x: Age Class
    • N_x: Number of Survivors
    • l_x: Survivorship
    • m_x: Age-Specific Fecundity
    • lxmx: Average Births/Year/Original Female
  • Example Data Points:
    • Age 0: Nx = 1000, lx = 1.000, mx = 0.00, lxm_x = 0.00
    • Age 2: Nx = 308, lx = 0.308, mx = 1.47, lxm_x = 0.45
    • Age 5: Nx = 10, lx = 0.010, mx = 3.25, lxm_x = 0.04
  • R0 = [Sigma] lxm_x = 1.00 (Net reproductive rate)

Survivorship Curves

  • Sex-specific survival (e.g., Belding’s ground squirrels).
  • Three basic survivorship curves.
  • Can be species or stage-specific.

Population Growth Parameters

  • R_0: Net reproductive rate.
  • r_{max}: Intrinsic per capita rate of increase (or population growth) = birth rate (b) - death rate (d), estimated as r.
  • K: Carrying capacity.

Life-History Continuum

  • Low Fecundity, High Survivorship: Few offspring, large offspring, late maturity, large body size, high disease resistance, high predator resistance, long life span.
  • High Fecundity, Low Survivorship: Many offspring, small offspring, early maturity, small body size, low disease resistance, low predator resistance, short life span.

Population Growth Equations

  • Exponential Growth:
    • \frac{dN}{dt} = r_{max}N
  • Logistic Growth:
    • \frac{dN}{dt} = r_{max}N \frac{K - N}{K}
    • Alternatively: \frac{dN}{dt} = r_{max}N (1 - \frac{N}{K})
  • Density Dependence: Growth rate slows at high density.

Density Dependence

  • Survival of gobies declines at high population density.
  • Fecundity of sparrows declines at high population density.

Density-Dependent Factors Limiting Population Size (Table 51.2)

  • Competition for resources: food, territory, water, light, nesting sites, nutrients, oxygen.
  • Disease and parasitism: infectious disease, parasitism.
  • Stress-related degradation of health.
  • Toxic wastes: ammonia, uric acid, alcohol, carbon dioxide.
  • Social behavior: stress-mediated behavior, dominance behavior, mating behavior, parental-care behavior, predator-avoidance behavior.
  • Predation: increased predation as prey density increases.

Hare-Lynx Population Cycle

  • Cycles every 10 years on average; changes in lynx density lag behind changes in hare density.

Hypotheses

  • Research Question: What factors control the hare-lynx population cycle?
  • Bottom-Up Hypothesis: Food availability for the hares controls the cycle.
  • Top-Down Hypothesis: Predation controls the cycle.
  • Interaction Hypothesis: Interaction of food availability and predation controls the cycle.
  • Null Hypothesis: The hare-lynx cycle isn't driven by predation, food availability, or a combination of those two factors.

Conclusion

  • Hare populations are limited by both predation and food availability.
  • When predation and food limitation occur together, they have a greater effect than either factor does independently.