I. Nature of population biology A. Major areas of population biology (2) 1. Population genetics 2. Population ecology - this course

1. Population Genetics a.origin and maintenance of genetic variation and diversity 1.Relative amount of polymorphic vs. monomorphic 2.Relative amount of heterozygosity vs. homozygosity b. evolutionary consequences of genetic change 1. Theory based in Mendelian laws and processes of Natural Selection 2. Management - sophisticated hybridization programs used in agriculture, medicine, insect management 3. Rare species – Population Viability Analysis (PVA)

2. Population Ecology - this course: a. relationships of population to their environment and each other b. number of individuals, not gene frequency 1. Theory - less basis than population Genetics a. mathematics of growth b. limits on growth 2. Management - based somewhat on theory but more on empirical data where theory is weak

B. History of Population Ecology a.Thomas Malthus - human populations and geometric (exponential) growth cannot continue (1798) b.P. F. Verhulst - logistic growth (1838) c.J. Von Liebig - “law of the minimum” (1840) d.F. F. Blackman - “law of limiting factors” (1905)

e. A. J. Lotka – predator-prey systems (1925) f. V. Volterra – predator-prey and competition (1926) g. Raymond Pearl - formalized logistic (1927) h. G. F. Gause - “The Struggle for Existence” Competition, theory and empirical data; classic experiments (1934) i.Nicholson A. J., and J. P. Bailey - population prediction and equilibrium (1935) History, continued

j. P. H. Leslie - projection matrices for population prediction and determination of equilibrium levels (1945) k. W. F. Lidicker - dispersal theory & regulation of #’s below carrying capacity (1962) l. George Innis - mathematician turned ecologist - computer modeling and stochastic models - filling the country with modelers (1970's).

C. Population study - an overview 1. Definition of “population” group of organisms of a single species which occupies a particular space at a particular time. 2. Population has some characteristics of individual a.Structure and life history - like individual 1.Grow, differentiate and respond to environment b. Characters unique to groups 1.Density, birth and death rates, sex and age structure, spatial distribution 2.These characters (properties) are the main subject matter of population ecology.

3. The study of factors affecting spatial and temporal patterns in the number of individuals a.Reproductive rates and mortality b.Dispersal and migration c.population structure d.regulatory mechanisms and e.interspecies relationships 4. Major questions a.What factors are involved in regulation of population size? b.What relationships exists between stability and complexity? c.What are the limiting factors?

5. Limiting vs. Regulating factors a.Limiting: what causes carrying capacity to be at a certain level; K=c b.Regulating factors: what causes change in population level to be zero; Δn = 0 c.Controversy 1. David Lack’s food hypothesis vs. Christian’s hormonal (adreno-pituitary) system: n regulated below food level 2. Fluctuating K - use avg. (K)

6. Density dependent vs. independent a.Dependent - a factor which affects a varying percentage of the population depending on its density 1. Parasites, disease, predation and competition (the biotic factors) are often density-dependent b. Independent - factors which affect a constant percentage 1.Weather (the physical factors) c. Controversy - entomologists from Australia 1.A. J. Nicholson: Population equilibrium, especially competition, was brought about by density-dependent effects 2. Andrewartha and Birch - a book in ) “equilibrium is a fiction” and 2) no environmental factors can operate in a density-independent way.

7. Solution of ecological problems a. Objectives and hypotheses b. Tests of hypotheses 1.Sampling and data analysis (empirical) 2.Model formulation and analysis c. Predictions and general theory

8. Laboratory and field studies a.Lab: carefully controlled experiments allow for direct hypothesis testing 1.Insect, plants, and micro-cosm experiments 2.Small mammals 3.A few larger small-mammal predator-prey studies b.Field: important to understand natural populations 1.Plants and animals 2.Short-term vs. long-term a lack long-term data for making needed generalizations

9. Looking for generalizations: SCIENCE a.Not get too caught up in the peculiarities of an individual population, but look for the generalizations that can be made 1. Plant ecologists: afraid of the community idea now (Gleason vs. Clements) 2. Population genetics: not worried about patterns that don’t fit simple allele system - modified b. Do not over-simplify or be incomplete 1. problems are complex and individual

10. Mathematical or Quantitative ecology a.Not statistics 1. Statistics is a branch of mathematics dealing with number distributions and probability b.Dealing with quantities in ecology 1.N 2.Rates affecting N 3.Factors quantitative effect on rates c.Use calculus and statistics 1.Calculus: rates of change, solutions to equations, stability, projections, instantaneous rates 2.Statistics: correlation of factors with population, mean, variance, confidence, significance, etc.

Summary 1.Course will cover population ecology 2.Not very old science with few laws 3.Variety of population characteristics are studied by using a variety of methods 4.Highly quantitative by nature