Transcript INTRODUCTION - Information technology

Population Distribution and
Abundance
Chapter 9
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Introduction
• Ecologists usually define a _____________ as
a group of individuals of a single species
inhabiting a specific area.
– Characterized by the number of individuals and
their ____________.
• Additional characteristics of a population …
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Distribution Limits
• _________________________limits
geographic distribution of a species.
– Organisms can only compensate so much for
environmental variation.
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Niches
• __________: Summarizes environmental
factors that influence growth, survival, and
reproduction of a species.
– Grinnell’s definition focused on the effects of …
– Elton’s definition included …
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Niches
• Hutchinson defined niche as:
– n-dimensional hyper-volume
• n equates to…
– _______________________- hypervolume
– _______________________ -includes
interactions such as competition that may restrict
environments where a species may live.
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Kangaroo Distributions and Climate
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Kangaroo Distributions and Climate
• Limited distributions may not be directly
determined by climate.
– Climate often influences species distributions via:
•
•
•
•
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Tiger Beetle of Cold Climates
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Distributions of Plants Along a
Moisture-Temperature Gradient
• Encelia species distributions correspond to
variations in temperature and precipitation.
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Distributions of Barnacles Along an
Intertidal Exposure Gradient
• Organisms living in an intertidal zone have
evolved to different degrees of resistance to
drying.
– Barnacles show distinctive patterns of zonation
within intertidal zone.
• Connell found Chthamalus stellatus restricted to upper
levels while Balanus balanoides is limited to middle and
lower levels.
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Distributions of Barnacles Along an
Intertidal Gradient
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Distributions of Barnacles Along an
Intertidal Gradient
• Balanus appears to be more vulnerable to …
• Chthamalus adults appear to be excluded
from lower areas by …
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Distribution of Individuals on Small
Scales
• __________: Equal chance of being anywhere.
– ________________of resources.
• __________: Uniformly spaced.
–
–
• __________: Unequal chance of being anywhere.
–
– Patchy …
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Distribution of Individuals on Small
Scales
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Distribution of Tropical Bee Colonies
• Hubbell and Johnson predicted aggressive bee
colonies would show regular distributions while
non-aggressive species would show random or
clumped distributions.
– As predicted, four species with regular distributions
were highly aggressive.
• Fifth was non-aggressive and randomly distributed.
• Prospective nest sites marked with pheromones.
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Distributions of Desert Shrubs
• Traditional theory suggests desert shrubs are…
– Phillips and MacMahon found distribution of
desert shrubs changes from …
– Young shrubs clumped for (3) reasons:
•
•
•
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Distributions of Desert Shrubs
• Phillips and MacMahon proposed as plants grow,
some individuals in clumps die, reducing
clumping.
–
• Eventually creates …
• Brisson and Reynolds found competitive
interactions with neighboring shrubs appear to
influence distribution of creosote roots, Larrea
tridentata.
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• Google Earth…
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Distributions of Individuals on Large
Scales
• Bird Populations Across North America
– Root found at continental scale, bird populations
showed clumped distributions in Christmas Bird
Counts.
– Clumped patterns occur in species with
widespread distributions.
– Brown found a relatively small proportion of study
sites yielded most of records for each bird species
in Breeding Bird Survey.
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Plant Distributions Along Moisture
Gradients
• Whittaker examined distributions of woody
plants along moisture gradients in several North
American mountain ranges.
– Documented moisture gradient from moist canyon
bottoms up to the dry southwest-facing slopes.
• Tree species showed a highly clumped distribution along
moisture gradients, with densities decreasing substantially
toward the edges of their distribution.
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Plant Distributions Along Moisture
Gradients
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Organism Size and Population Density
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Organism Size and Population Density
• In general, population density declines with
increasing organism size.
– Damuth found the population density of herbivorous
mammals decreased with increased body size.
– Peters and Wassenberg found aquatic invertebrates
tend to have higher population densities than
terrestrial invertebrates of similar size.
– WHY?!?
• Mammals tend to have higher population densities than
birds of similar size.
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Plant Size and Population Density
• Plant population density decreases with
increasing plant size.
– Underlying details are very different.
• Tree seedlings can live at very high densities, but as the
trees grow, density declines progressively until mature
trees are at low densities.
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Commonness and Rarity
• Rabinowitz devised commonness classification
based on (3) factors:
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•
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• Populations that are least threatened by
extinction, have extensive geographic ranges,
broad habitat tolerances, and some large local
populations.
– All seven other combinations create some kind of
rarity.
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Rarity
• Rarity I
–
• Peregrine Falcon
• Rarity II
http://falconrytoday.net/news/wp-content/uploads/2009/08/Peregrine-Falcon0014.jpg
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• Passenger Pigeon
http://www.saroffillustration.com/portfolio/page/ns4_pigeon.jpg
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Rarity
• Rarity III
–
• California Condor
http://www.dfg.ca.gov/wildlife/hunting/condor/images/condor119.jpg
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