, Natural “Nothing in biology makes sense except in the light of evolution.” Selection, and Adaptation (Theodosius Dobzhansky)

Charles Darwin (1809-1882)

• Voyage of HMS Beagle (1831-1836) • Thinking about & collecting supporting evidence (1837-1858) • Origin of Species (1859)

(HMS Beagle) Alfred Russel Wallace (1823-1913)

• Natural history collecting trips to Brazil and SE Asia • Author of The Malay Archipelagio • Wrote a letter to Darwin explaining his idea of natural selection - 1858

“…as many more individuals of a species are Evolution via Natural Selection born than can possibly survive and, as there is • Process whereby heritable traits that confer the a frequently recurring struggle for existence, it highest relative reproductive success increase in follows that any being, if it vary however frequency over evolutionary time slightly in any manner profitable to itself, under the complex and sometimes varying conditions of life, will have a better chance of surviving, and thus be naturally selected. From the strong principle of inheritance, any selected variety will tend to propagate its new modified form.” (Origin of Species, 1859) Definitions Artificial Selection • Process whereby humans selectively breed some varieties over others, causing one or more varieties to • Natural selection: Differential reproduction and increase in frequency survivorship among individuals within a population • Fitness: relative lifetime reproductive success • Survival & Reproduction • Adaptation: trait that increases the fitness of an individual, relative to its competitors, in a

population. (Dugatkin, 2004)

Time to go fishing! Time to go fishing! • Start with 5 of each color in your pond • Mix them up well • Use only chopsticks in one hand to fish • Keep caught “fish” in pile • At the end of each round, count the number of each color fish that you caught • Each surviving fish replicates at the end of each round • Keep track of how many of each color you add to the pond Fishing for M & M’s Natural selection occurs when… • Why wouldn’t populations evolve to have only one color, for example, only red M&M’s? 1. Trait is variable within a population • Are we stuck with only five colors of M&M’s forever? 2. Variation contributes to differences in What if the environment changed to a new color, such reproductive success as black? What would happen? 3. Variation is heritable • Why is variation useful?

Variation within a population

Due to: 1. Differences in genetic composition 2. Differences in environmental conditions 3. Differences in learning

Figure 2.4.Honeybee food delivery. From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press Variation within a population Variation may not affect fitness

Due to: Eastern screech owls show 1. Differences in genetic composition great variation in dispersal 2. Differences in environmental conditions direction 3. Differences in learning And 1. Variation in traits may not affect fitness 2. Frequency-dependent selection can maintain different traits in a population

From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press

Frequency-dependant Selection Frequency-dependant Selection

Positive frequency- Negative frequency- dependent selection: dependent selection: the fitness of a trait the fitness of a trait increases as it becomes decreases as it becomes more common more common Frequency-dependant Selection Origin of new traits

New traits originate by:

random changes in genetic material (mutation, sexual recombination)

survive or disappear due to selection by environmental factors (thus affecting the composition of the population as a whole).

Lamarckism • ‘Inheritance of Genetics acquired characters’ • Gene: segment of protein-encoding DNA • Useful characters are acquired during the • Allele: variant of a gene lifetime of an organism and • Gene pool: sum of all alleles in the population passed on to offspring. Characters that are not • Evolution: change in the allelic frequency of a useful are diminished. population • Continuous, gradual • Heritable: A genetically-based trait that can change (Jean-Baptiste Lamarck, 1809, Philosophie Zoologique) be passed from parents to their offspring Measures of

1. Parent-offspring regression analysis: – Examines the similarity between parents and their offspring in terms of the traits they possess – If a trait has a genetic basis, then the trait values of offspring should be similar to the trait values of their parents: there should be a positive relationship between offspring and parent trait values 2. Selection experiment method: – Different groups of individuals are subjected to differential selection on the trait in question – If artificial selection acting on a trait results in changes in that trait value in subsequent generations, then the trait has a genetic basis

From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press

Adaptation and Selection experiment Tinbergen’s 4 Levels • Over four generations of selection, found strong changes in exploratory behavior

From Nordell and Valone, Animal Behavior: Concepts, Methods, and Applications, © 2014 by Oxford University Press F

Adaptationist Approach to Adaptation Study of Behavior

a trait that increases the fitness of an individual, • What methods are employed to determine if and how relative to others in its population behaviors are adaptive?

Aren’t all traits adaptive? Constraints on Adaptive Perfection

1. of appropriate mutations to occur • Selection can’t keep up with environmental change

Not all traits are adaptive, AND those that are adaptive are not perfect.