Latitudinal Gradients in Avian Clutch Size

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Latitudinal Gradients in Avian Clutch Size

• Daylength Hypothesis
• Prey Diversity Hypothesis (search images)
• Spring Bloom or Competition Hypothesis
• Nest Predation Hypothesis (Skutch)
• Hazards of Migration Hypothesis
• Please study Handouts 1, 2, 3, and 4 in
  preparation for next Thursdays exam

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Evolution of Death Rates, Senescence, old age,
genetic dustbinMedawars Test Tube Model,
Lactose intolerance Recession of time of
expression of the overt effects of a detrimental
allele Precession of time of expression of the
positive effects of a beneficial
allele Pearl-Verhulst Logistic Equation
Sigmoidal Population Growth Density Dependence
versus Density Independence Density Dependent
versus Density Independent Selection Equilibrium,
Opportunistic, and Fugitive Species r-strategists
versus K-strategists
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What starts off slow, finishes in a flash . . .
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S - shaped sigmoidal population growth
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Verhulst-Pearl Logistic Equation dN/dt rN
rN (N/K) rN (rN2)/K dN/dt rN 1
(N/K) rN (K N)/K dN/dt 0 when (K
N)/K 0 (K N)/K 0 when N K dN/dt
rN (r/K)N2
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Inhibitory effect of each individual On its own
population growth is 1/K
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At equilibrium, birth rate must equal death rate,
bN dN bN b0 x N dN d0 y
N b0 x N d0 y NSubstituting K
for N at equilibrium and r for b0 d0
r (x y) K or K r/(x y)
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Derivation of the Logistic Equation Derivation
of the VerhulstPearl logistic equation is easy.
Write an equation for population growth using
the actual rate of increase rN
dN/dt rN N (bN dN) N
Substitute the equations for bN and dN into
this equation dN/dt
(b0 xN) (d0 yN) N
Rearrange terms,
dN/dt (b0 d0 ) (x y)N) N
Substituting r for (b d)
and, from above, r/K for (x y), multiplying
through by N, and rearranging terms,
dN/dt rN
(r/K)N2
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Density Dependence versus Density Independence
Dramatic Fish Kills, Illustrating
Density-Independent Mortality ____________________
___________________________________
Commercial Catch Percent
Locality Before After Dec
line _____________________________________________
__________ Matagorda 16,919 1,089
93.6 Aransas 55,224 2,552 95.4 Laguna
Madre 12,016 149 92.6 _____________________
___________________________________ Note These
fish kills resulted from severe cold weather on
the Texas Gulf Coast in the winter of 1940.
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Parus major
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Fugitive species
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Some of the Correlates of r- and K-Selection
____________________________________
__________________________________________________
_


r-selection K-selection
_________________________________________________
__________________________________________________
___________________________ Climate Variable and
unpredictable uncertain Fairly constant
or predictable more certain Mortality Often
catastrophic, nondirected, More directed,
density dependent density independent
Survivorship Often Type III Usually Types I
and II Population size Variable in time,
nonequil- Fairly constant in time, ibrium
usually well below equilibrium at or
near carrying capacity of envi- carrying
capacity of the ronment unsaturated
com- environment saturated munities or
portions thereof communities no
recolon- ecologic vacuums recolon- ization
necessary ization each year Intra- and
inter- Variable, often lax Usually
keen specific competition Selection favors 1.
Rapid development 1. Slower development 2.
High maximal rate of 2. Greater competitive
ability increase, rmax 3. Early
reproduction 3. Delayed reproduction 4. Small
body size 4. Larger body size 5. Single
reproduction 5. Repeated reproduction 6. Many
small offspring 6. Fewer, larger progeny Length
of life Short, usually less than a year Longer,
usually more than a year Leads
to Productivity Efficiency Stage in
succession Early Late, climax _________________
__________________________________________________
__________________________________________________
___________
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Kirk Winemiller
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From Molles and Cahill, Ecology Concepts and
Applications
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Population Regulation Ovenbird example
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Frequencies of Positive and Negative Correlations
Between Percentage Change in Density and
Population Density for a Variety of Populations
in Different Animal Groups ______________________
_____________________________________________
Numbers of Populations in Various
Categories _____________________________________
_______ Positive Positive Negative
Negative Negative Taxon (Plt.05) (Not sig.)
(Not sig.) (Plt.10) (P lt .05) Total
_________________________________________________
__________________

Inverts 0
0 0 0 4
4 Insects 0 0 7
1 7 15 Fish 0 1
2 0 4 7 Birds
0 2 32 16
43 93 Mammals 1 0
4 1 13 19
Totals 1 3 45
18 71 138 ________________
__________________________________________________
_ Homo sapiens (the sap)
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Negative correlations between percentage change
in density and population density for
a variety of populations in
different animal groups except for Homo the sap
4 and 10 year population cycles microtines and
snowshoe hares Sunspot Hypothesis dark tree
ring marks Time Lags Stress Phenomena
Hypothesis Predator-Prey Oscillations
Epidemiology-Parasite Load Hypothesis Food
Quantity Hypothesis Nutrient Recovery Other
Food Quality Hypotheses Genetic Control
Hypothesis Optimal reproductive tactics Could
optimal reproductive tactics drive population
cycles?
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Notice apparent 10-year periodicity
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Snowy owls
Microtines Voles and lemmings 4 year cycles
Fabled lemming marches into the sea
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Disneys White Wilderness movie
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Dennis Chitty Charles Krebs A. Sinclair
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Population Cycles

• Sunspot Hypothesis
• Time Lags
• Stress Phenomena Hypothesis
• Predator-Prey Oscillations
• Epidemiology-Parasite Load Hypothesis
• Food Quantity Hypothesis
• Nutrient Recovery
• Other Food Quality Hypotheses
• Genetic Control Hypothesis
• BbRead Krebs et al. What drives the 10-year
  cycle of snowshoe hares?