Exam next Thursday:

Chapters 1, 8, and 9

Ten (Eleven) Readings:Spaceship EarthNee's “The Great Chain of Being”, NatureKlinkenborg's “Depth of Time”, NY TimesMorrison's “Evolution's Problem Gamblers”Scientific MethodsNatural SelectionHuman InstinctsOur Hunter-Gatherer HeritagePopulation GrowthEvolution of Uncaring Humanoids

Plus Krebs et al. on Snowshoe hare 10-year “cycles”

Handouts 1, 2, 3, and 4

Pearl-Verhulst Logistic Equation: Sigmoidal Population Growth

Density Dependence versus Density Independence

Density Dependent versus Density Independent Selection

Equilibrium, Opportunistic, and Fugitive Species

r-K selection continuum, r-strategists versus K-strategists

Winemiller’s 3D life history plot

Negative Correlations Between % Change in Density and Population Density

Pearl-Verhulst Logistic EquationK = Carrying capacity

dN/dt = rN [(K – N)/K]= rN {1– (N/K)} = rN – (r/K)N2

dN/dt = 0 when [(K – N)/K] = 0[(K – N)/K] = 0 when N = K

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 NegativeTaxon (P<.05) (Not sig.) (Not sig.) (P<.10) (P < .05) Total ___________________________________________________________________ Inverts 0 0 0 0 4 4Insects 0 0 7 1 7 15Fish 0 1 2 0 4 7Birds 0 2 32 16 43 93Mammals 1* 0 4 1 13 19 Totals 1* 3 45 18 71 138___________________________________________________________________* Homo sapiens (the “sap”)

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

Bb: Read Krebs et al. “What drives the 10-year cycle of snowshoe hares?”

Also, please study Handouts 1, 2, 3, and 4 in preparation for

next Thursday’s exam

Notice apparent 10-year periodicity

Microtines: Voles and lemmings: 4 year cycles Fabled lemming marches into the sea

Snowy owls

Disney’s “White Wilderness” movie

Dennis Chitty Charles Krebs A. Sinclair

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

Bb: Read Krebs et al. “What drives the 10-year cycle of snowshoe hares?”

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

Sunspot Hypothesis (Sinclair et al. 1993. Am. Nat.)

10 year cycle embedded within 30-50 year periods

Maunder minimum: 1645-1715

Three periods of high sunspot maxima:

1751-1787 1838-1870 1948-1993

Canadian Government Hare Survey 1931-1948

Hare cycle synchronized across North America

Yukon: 5 km strip, tree growth rings (N = 368 trees)

One tree germinated in 1675 (>300 years old)

Hares prefer palatable shrubs, but will eat spruce

Leaving dark tree ring marks

A. Sinclair

Maunder Minimum

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

Other Food Quality Hypotheses:

Microtus: palatability <–––> toxic (Freeland 1974)

Snowshoe hares: Plant chemical defenses against herbivory

Chitty’s “Genetic Control” Hypothesis

Could optimal reproductive tactics be involved in driving population cycles?

Dennis Chitty