Lack - Avian clutch size and parental care Great tit, starling, chimney swift Delayed reproduction in seabirds, especially albatrosses Latitudinal Gradients in Avian Clutch Size Daylength Hypothesis Prey Diversity Hypothesis Spring Bloom or Competition Hypothesis Nest Predation Hypothesis (Skutch) Hazards of Migration Hypothesis Evolution of Death Rates Senescence, old age, genetic dustbin Medawar’s Test Tube Model recession of time of expression of overt effects of a detrimental allele precession of time of expression of effects of a beneficial allele S - shaped sigmoidal population growth Verhulst-Pearl Logistic Equation: dN/dt = rN [(K – N)/K]

Some of the Correlates of r- and K-Selection _______________________________________________________________________________________ r-selection K-selection _______________________________________________________________________________________ ClimateVariable and unpredictable; uncertain Fairly constant or predictable; more certain MortalityOften catastrophic, nondirected, More directed, density dependent density independent SurvivorshipOften Type III Usually Types I and II Population sizeVariable in time, nonequilibrium; Fairly constant in time, ibrium; usually well below equilibrium; at or near carrying capacity of environment; carrying capacity of the unsaturated communities or environment; saturated portions thereof; ecologic vacuums; communities; no recolonization recolonization each year necessary Intra- and inter-Variable, often laxUsually keen specific competition Selection favors1. Rapid development1. Slower development 2. High maximal rate of2. Greater competitive ability increase, r max 3. Early reproduction3. Delayed reproduction 4. Small body size4. Larger body size 5. Single reproduction5. Repeated reproduction 6. Many small offspring6. Fewer, larger progeny Length of lifeShort, usually less than a year Longer, usually more than a year Leads toProductivityEfficiency Stage in successionEarlyLate, climax __________________________________________________________________

Dr. Kirk Winemiller Texas A & M. Univ. Mola mola Gambusia Sharks, skates, and Rays Mosquito Fish Sturgeon

Dr. Kirk Winemiller Texas A & M. Univ. Cocoa Nut Tree Sequoia Tree Dandelion

Population Regulation [Ovenbird example]

Frequencies of Positive and Negative Correlations Between Percentage Change in Density and Population Density for a Variety of Populations in Different Taxa _________________________________________________________________ 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

Notice apparent 10-year periodicity Hudson Bay Company

Hudson's Bay was incorporated on 2 May 1670, with a royal charter from King Charles II. The charter granted the company a monopoly over the region drained by all rivers and streams flowing into Hudson Bay in northern Canada. The area gained the name "Rupert's Land" after Prince Rupert, the first governor of the company appointed by the King. This drainage basin of Hudson Bay constitutes 1.5 million square miles, comprising over one-third of the area of modern-day Canada and stretches into the present-day north-central United States. The specific boundaries were unknown at the time. Rupert's Land would eventually become Canada's largest land "purchase" in the 19th century.

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 survey Hare cycle synchronized across North America Yukon: 5km 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

CH 4 C0 2 °C

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?

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

Social Behavior Hermits must have lower fitness than social individuals Clumped, random, or dispersed (variance/mean ratio) mobility = motility = vagility (sedentary sessile organisms) Use of Space Philopatry Fluid versus Viscous Populations Individual Distance, Daily Movements Home Range Territoriality (economic defendability) Resource in short supply Feeding Territories Nesting Territories Mating Territories

V V Net Benefit

Sexual Reproduction Monoecious versus Diecious Evolution of Sex —> Anisogamy Diploidy as a “fail-safe” mechanism Costs of Sexual Reproduction (halves heritability!) Facultative Sexuality (Ursula LeGuin -- Left Hand of Darkness) Protandry Protogyny (Social control) Parthenogenesis (unisexual species) Possible advantages of sexual reproduction include: two parents can raise twice as many progeny mix genes with desirable genes (enhances fitness) reduced sibling competition heterozygosity biparental origin of many unisexual species

Male Female Female = Male Female No Sex Change Protogyny Protandry Robert Warner

Why have males? “The biological advantage of a sex ratio that is unbalanced in favor of females is readily apparent in a species with a promiscuous mating system. Since one male could fertilize several females under such a system, survival of a number of males equal to the number of females would be wasteful of food, home sites, and other requirements for existence. The contribution of some of the surplus males to feeding the predators on the population would be economically advantageous. In other words, the eating of the less valuable (to the population) males by predators would tend to reduce the predator pressure on the more valuable females.” — Blair (1960) The Rusty Lizard W. Frank Blair Sceloporus olivaceus

Sex Ratio Proportion of Males Primary, Secondary, Tertiary, Quaternary Why have males? Fisher ’ s theory: equal investment in the two sexes Ronald A. Fisher

Comparison of the Contribution to Future Generations of Various Families in Case a in Populations with Different Sex Ratios __________________________________________________________________ Case a Number of MalesNumber of Females __________________________________________________________________ Initial population Family A 4 0 Family C 2 2 Subsequent population (sum) C A = 4/106 = C C = 2/ /102 = (family C has a higher reproductive success) __________________________________________________________________ Note: The contribution of family x is designated C x.

Comparison of the Contribution to Future Generations of Various Families in Case a in Populations with Different Sex Ratios __________________________________________________________________ Case a Number of MalesNumber of Females __________________________________________________________________ Initial population Family E 0 4 Family C 2 2 Subsequent population (sum) C E = 4/106 = C C = 2/ /102 = (family C has a higher reproductive success) __________________________________________________________________ Note: The contribution of family x is designated C x.

Comparison of the Contribution to Future Generations of Various Families in Case a in Populations with Different Sex Ratios __________________________________________________________________ Case a Number of MalesNumber of Females __________________________________________________________________ Initial population Family A 4 0 Family C 2 2 Family E 0 4 Subsequent population (sum) C A = 4/106 = C C = 2/ /106 = All three families have equal success C E = 4/106 = __________________________________________________________________ Note: The contribution of family x is designated C x.

___________________________________________________________________________ Case bNumber of MalesNumber of Females ____________________________________________________________________________ Initial population Family A 2 0 Family B 1 2 Subsequent population (sum) C A = 2/103 = C B = 1/ /102 = (family B is more successful) Initial population Family B 1 2 Family C 0 4 Subsequent population (sum) C B = 1/ /106 = C C = 4/106 = (family C is more successful than family B) Natural selection will favor families with an excess of females until the population reaches its equilibrium sex ratio (below). Initial population Family B 1 2 Family C 0 4 Subsequent population (sum) C B = 1/ /206 = C C = 4/206 = (family B now has the advantage) _____________________________________________________________________________ Note: The contribution of family x is designated C x.

Differential Mortality of the sexes during the period of parental care.

Differential Mortality of the sexes during the period of parental care