N = 5290 Species

Lack - Avian clutch size and parental careGreat tit, starling, chimney swift

Delayed reproduction in seabirds, especially albatrossesLatitudinal Gradients in Avian Clutch Size

Daylength HypothesisPrey Diversity HypothesisSpring Bloom or Competition Hypothesis Nest Predation Hypothesis (Skutch)Hazards of Migration Hypothesis

Evolution of Death Rates

Senescence, old age, genetic dustbinMedawar’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 _______________________________________________________________________________________ Climate Variable and unpredictable; uncertain Fairly constant or predictable; more certain

Mortality Often catastrophic, nondirected, More directed, density dependentdensity independent

Survivorship Often Type III Usually Types I and IIPopulation size Variable in time, nonequilibrium; Fairly constant in time,

ibrium; usually well below equilibrium; at or nearcarrying capacity of environment; carrying capacity of theunsaturated communities or environment; saturatedportions thereof; ecologic vacuums; communities; no recolonizationrecolonization each year necessary

Intra- and inter- Variable, often lax Usually keenspecific competitionSelection favors 1. Rapid development 1. Slower development

2. High maximal rate of 2. Greater competitive ability increase, rmax 3. Early reproduction 3. Delayed reproduction4. Small body size 4. Larger body size5. Single reproduction 5. Repeated reproduction6. 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 EfficiencyStage in succession Early Late, climax__________________________________________________________________

Dr. Kirk WinemillerTexas A & M. Univ.

Molamola

GambusiaSharks, skates,and RaysMosquito Fish

Sturgeon

Dr. Kirk WinemillerTexas 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 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

http://www.commondreams.org/view/2011/03/07-0

Notice apparent 10-year periodicity

Hudson Bay Company

Hudson Bay CompanyHudson'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

http://www.commondreams.org/view/2011/03/07-0

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 survey 1931-1948

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

CH4

C02

°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 beinvolved 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 individualsClumped, random, or dispersed (variance/mean ratio)mobility = motility = vagility (sedentary sessile organisms)

Use of SpacePhilopatryFluid versus Viscous Populations

Individual Distance, Daily MovementsHome RangeTerritoriality (economic defendability)Resource in short supply

Feeding TerritoriesNesting TerritoriesMating Territories

V

V

NetBenefit

Sexual Reproduction

Monoecious versus DieciousEvolution of Sex —> AnisogamyDiploidy as a “fail-safe” mechanismCosts 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 competitionheterozygositybiparental origin of many unisexual species

Male

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 MalesPrimary, Secondary, Tertiary, QuaternaryWhy 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 Males Number of Females__________________________________________________________________Initial population 100 100

Family A 4 0Family C 2 2

Subsequent population (sum) 106 102CA = 4/106 = 0.03773CC = 2/106 + 2/102 = 0.03846 (family C has a higher reproductive success)

__________________________________________________________________

Note: The contribution of family x is designated Cx.

Comparison of the Contribution to Future Generations of Various Families in Case a in Populations with Different Sex Ratios__________________________________________________________________Case a Number of Males Number of Females

__________________________________________________________________

Initial population 100 100Family E 0 4Family C 2 2

Subsequent population (sum) 102 106

CE = 4/106 = 0.03773CC = 2/106 + 2/102 = 0.03846 (family C has a higher reproductive success)

__________________________________________________________________

Note: The contribution of family x is designated Cx.

Comparison of the Contribution to Future Generations of Various Families in Case a in Populations with Different Sex Ratios__________________________________________________________________Case a Number of Males Number of Females

__________________________________________________________________

Initial population 100 100Family A 4 0Family C 2 2Family E 0 4

Subsequent population (sum) 106 106

CA = 4/106 = 0.03773CC = 2/106 + 2/106 = 0.03773 All three families have equal successCE = 4/106 = 0.03773

__________________________________________________________________

Note: The contribution of family x is designated Cx.

___________________________________________________________________________Case b Number of Males Number of Females____________________________________________________________________________Initial population 100 100

Family A 2 0Family B 1 2

Subsequent population (sum) 103 102CA = 2/103 = 0.01942CB = 1/103 + 2/102 = 0.02932 (family B is more successful)

Initial population 100 100Family B 1 2Family C 0 4

Subsequent population (sum) 101 106CB = 1/101 + 2/106 = 0.02877CC = 4/106 = 0.03773 (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 100 200

Family B 1 2Family C 0 4

Subsequent population (sum) 101 206CB = 1/101 + 2/206 = 0.001971CC = 4/206 = 0.01942 (family B now has the advantage)

_____________________________________________________________________________Note: The contribution of family x is designated Cx.

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

Differential Mortality of the sexes during the period of parental care