Transcript Habitat & Niches - Sayedmaulana's Blog

Habitat & Niches
24 June 2009
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Habitat
• Totality of environment factors in which a
population or species regularly lives.
• Space and time
– Physical and biotic environment
– Vegetation
• Forest, meadow, pasture, coniferous forest, etc.
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Habitat
• Habitats may be subdivided into layers or
zones
– Microhabitats
•
•
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Forest canopy: leaves, branches
Shrub layer: leaves, branches, trunks
Herb layer: leaves, stems, mosses, ferns
Litter: dead fallen leaves, logs,
– Varies in depth, quality
• Soil: topsoil, subsoil
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Niche
• Species’/population’s role in its community
– Dimensions of a niche:
• Habitat & microhabitat (Space occupied)
• Food “spectrum,” essential nutrients
• Reproductive requirements
– Nutrition, nest/den sites
• Seasonality: When are resources required, used.
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Niche
• Fundamental niche
– All resources that could be used in absence of
competition.
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Niche
• Realized niche
– Resources actually used in presence of competitor.
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Niches
• Competitive exclusion
– When forced to
compete, one species
eliminates other(s)
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Niches
• Resource partitioning
avoids competition;
• Realized niches divide
resources (caterpillars)
among several species
of warblers.
• Each species evolved
& adapted to
specialized diet.
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Niches
• Character displacement
– Species evolve to
minimize competition
– Niche and morphologic
overlap when allopatric
– Difference and
specialization when
sympatric
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Keystone Species
• Species in a community with vital role in
community organization.
• Analogy to arch
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Keystone Species
• Species in a
community with vital
role in community
organization.
• Sea otter on North
America’s Pacific
Coast
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Keystone Species
• More examples:
– Sea stars on rocky
shores
– Dominant plant species
• Lupines in mountain
meadows
– “Top” carnivores
• Wolves in Yellowstone
National park
• Sharks on coral reefs
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• Invasive species may
prey on or parasitize
keystone
– Human removal of sea
otters, wolves, sharks
• Out-compete keystone
for space or resources
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Niches
• Invasive species
may prey on or
parasitize
keystone
– Sea lamprey
parasitizes large
predatory fishes
in Great Lakes.
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Niches
• Out-compete
keystone for space
or resources
– Imported fire ant
– Kudzu
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Niches
• Out-compete
keystone for space
or resources
– Purple loosestrife
– Zebra mussel
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Invasive species:
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–
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Kudzu
Fire ant
Zebra mussel
Purple loosestrife
Leafy spurge
Asian long-horned
beetle
– Emerald ash borer
– Japanese beetle
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– African honeybee
– Tiger mosquito
– Brown snake
• Guam
– European starling
– House sparrow
– More, & more, &
…
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