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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
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
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
