Exam next Thursday: Chapters 1, 8, and 9 Ten (Eleven) Readings: Spaceship Earth Nee's “The Great Chain of Being”, Nature Klinkenborg's “Depth of Time”, NY Times Morrison's “Evolution's Problem Gamblers” Scientific Methods Natural Selection Human Instincts Our Hunter-Gatherer Heritage Population Growth Evolution 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 Equation K = Carrying capacity dN/dt = rN [(K – N)/K] = rN {1– (N/K)} = rN – (r/K)N 2 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 Negative Taxon(P<.05) (Not sig.) (Not sig.) (P<.10) (P <.05) Total ___________________________________________________________________ Inverts Insects Fish Birds Mammals 1* Totals 1* ___________________________________________________________________ * 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 Am. Nat.) 10 year cycle embedded within year periods Maunder minimum: Three periods of high sunspot maxima: Canadian Government Hare Survey 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