Ecological Conditions

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Ecological Conditions
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Summary of the effects of conditions on species
distributions

• Lethal conditions may limit distributions but
  they only need to occur occasionally in order to
  do so.

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Saguaro cactus in snow
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Summary of the effects of conditions on species
distributions

• Distributions are more often limited by
  conditions that are regularly suboptimal (rather
  than lethal) leading to a reduction in growth or
  reproduction or increased chance of mortality.

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Summary of the effects of conditions on species
distributions

• Suboptimal conditions often act by altering the
  outcome of a biological interaction between the
  species of interest and other species.

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St. JohnsWort aka Klamath weed
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Chrysolina Beetles on St. Johns Wort
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Summary of the effects of conditions on species
distributions

• Suboptimal conditions often interact with other
  conditions so that it is often impossible to
  locate a single condition as the most important
  factor.

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Mediterranean fruit fly
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Summary of the effects of conditions on species
distributions

• Suboptimal conditions are often moderated by the
  evolutionary, physiological and behavioral
  responses of the organisms.

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Kangaroo Rat
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Summary of the effects of conditions on species
distributions

• Towards the edge of a species range, it occupies
  patches in which conditions are closest to those
  found in the center of its range.

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Rufous grasshopper
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Relative Humidity

• Relative humidity - is a measure of the amount of
  moisture in the air
• all terrestrial organisms must conserve water and
  prevent water loss to surrounding environment -
  in general the higher the relative humidity (the
  amount of water contained in the air) the less
  energy an organism has to expend to conserve water

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Transpiration
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Joshua Tree Xerophyte grow in dry habitats
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Water lily Hydrophyte grow in wet habitats
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Hepatica Mesophyte grow in moist habitats
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True Xerophyte leaf - Oleander
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Barrel cactus Succulent
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Desert Ephemerals South Africa
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Desert soil profile Phreatophytes with deep
root systems
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Soil pH

• plants suffer direct toxic effects when soil pH
  is below 3 or above 9 - there are naturally
  occurring soils which have these pH's
• However at more moderate pH there can be indirect
  effects

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Salinity

• For aquatic organisms the concentration of salt
  in the water presents a condition that limits
  distributions

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salinity gradient in an estuary
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Pollution

• Pollution - unfortunately this is becoming a
  condition which species must respond to
• Toxic effects - heavy metals in soils, often from
  mine tailings, are deposited onto soil in high
  concentrations
• 2. Acid precipitation

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Bent grass Agrostis tenuis
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Trees Burnt by Acid Precipitation Northeastern
U.S.
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Resources

• Resources are parts of the physical environment
  that are consumed (used up) by living organisms
  There are many different resources for plants
  solar radiation, soil nutrients, water, carbon
  dioxide, space
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• For animals primarily food sources, oxygen,
  space
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• For decomposers a supply of dead organic
  matter, oxygen (for some), space

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The Niche

• ecological niche - the way in which an organism
  interacts with all of the biotic and abiotic
  factors in its environment - often described as
  how the organism makes its living, its functional
  role, but includes the habitat it occupies

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G. Evelyn Hutchinson age 18
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N-dimensional niche
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Hutchinsons Niche Definitions

• The fundamental niche - the set of resources and
  conditions that permits the survival and
  reproduction of an organism - many resources and
  conditions interact to form the niche.
• The realized niche - the portion of the
  fundamental niche actually occupied by the
  species when restricted by other organisms -
  restricted by competition, predation, parasites,
  disease.
• - Hutchinson 1958