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11
Population DynamicsChapter 10
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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Dispersal in Rivers and Streams
• Stream dwellers have mechanisms to allow them to maintain their stream position.– Streamlined bodies– Bottom-dwelling– Adhesion to surfaces
• Tend to get washed downstream in spates.– Muller hypothesized populations maintained via
dynamic interplay between downstream and upstream dispersal.• Colonization cycle
1111
Metapopulations
• A metapopulation is made up of a group of subpopulations living on patches of habitat connected by an exchange of individuals.– Alpine Butterfly - Roland et al.– Lesser Kestrels - Serrano and Tella.
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Patterns of Survival
• Three main methods of estimation:– • Identify individuals born at same time and keep records
from birth.– • Record age at death of individuals.
– • Calculate difference in proportion of individuals in each
age class.• Assumes differences from mortality.
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High Survival Among the Young
• Murie collected Dall Sheep skulls, Ovis dalli.– Major Assumption: Proportion of skulls in each
age class represented typical proportion of individuals dying at that age.• Reasonable given sample size of 608.
– Constructed _________________________.• Discovered bi-modal mortality.
– <1 yr.– 9-13 yrs.
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Survivorship Curves
• : Majority of mortality occurs among older individuals. – Dall Sheep
• : Constant rate of survival throughout lifetime.– American Robins
• : High mortality among young, followed by high survivorship.– Sea Turtles
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Age Distribution
• Age distribution of a population reflects its history of survival, reproduction, and growth potential.
• Miller published data on age distribution of white oak (Quercus alba).– Determined relationship between age and trunk
diameter.– Age distribution biased towards young trees.• Sufficient reproduction for replacement.
– Stable population
1919
Age Distribution
• Rio Grande Cottonwood populations (Populus deltoides wislizenii) are declining.– Old trees not being replaced.– Reproduction depends on seasonal floods.• Prepare seed bed.• Keep nursery areas moist.
– Because floods are absent, there are now fewer germination areas.
2020
Rates of Population Change
• : Number of young born per female.
• : Tabulation of birth rates for females of different ages.