Download The overviews in Chapter 1: 1. How natural selection shapes

The overviews in Chapter 1:
1.  How natural selection shapes behavior.
2. How learning influences behavior.
3. How learning is aided in groups through
cultural transmission of information.
Example 1 of natural selection working on
animal behavior:
Parasite pressure, in populations of Hawaiian
crickets, changes mating behavior.
(Or does it? See last slide in this series.)
Parasite pressure in populations of Hawaiian crickets changes mating behavior
Parasitic fly finds male crickets by their mating call
Males with weaker calls survive better (but attract fewer females)
Selective balance favors mostly silent males
Silent males acquire “satellite” behavior to get females
(On some islands lots of parasitic flies, on other islands few)
“File” generates sound when wing rubbed
One assumes allelic variation in the genes
controlling wing ridges. Some individuals have
deeper ridges and make slightly louder sounds,
others shallower ridges.
Why doesn’t natural selection drive all
individuals to have the maximum ridge and
greatest sound?
Competing pressures! Perhaps deep ridges
require more force to rub. Crickets with deep
ridges can’t call for as long.
Given variation, predation pressure then favors
individuals with the shallow ridge allele (and
are not parasitized by flies).
Frequency of the shallow ridge alleles increases
in population.
Eventually get mostly silent males.
Ethological philosophy:
Did natural selection operate to change a
behavior?
Example 2 of natural selection working on
animal behavior:
Mole rats live in arid or in better environments
Arid environment
 scarce
resources  rats
should be more
Xenophobic.
Use aggression index as surrogate for xenophobia
From a scientific presentation perspective, what is wrong with
this diagram?
BTW, for “clinical” rat and mouse behavioral testing, some
companies make
turn-key systems.
The Noldus automated
aggression tester for
mice.
From the sales brochure: ”The Tube Test is a well-known test
paradigm designed to measure (altered) social dominance and
investigate social hierarchies in mice (Lindzey et al., 1961).
Traditionally, data are collected by human observers. The
Automated Tube Test is a novel apparatus that fully automates
the validated tube test procedures”
Match sessions: two mice are placed in their own start
box, walk through the tube, and compete in forcing the
other back into its start box.
Example of learning: grasshopper food preference
experiments
Give hoppers choice of better diet or crappy diet.
1.  Match dishes with colored cards & odors, or
2.  Scramble cards, odors and dishes
Citral or coumarin odor, Brown or green cards
Consistent cue pairing – hoppers
go right to the better food
Which of
Tinbergen’s
questions is
relevant for this
learned behavior?
(function)
Cultural transmission of learned information
The key distinction is vertical transmission
between generations.
Text example:
Rat 2 smells food odor
on rat 1; figures out (&
remembers) food with
that smell is good to eat.
Chapter 2
For natural selection to change the
behavior of a population of individuals:
1.  There must be variation in the trait.
2.  Trait variants lead to differential fitness.
(environmental control!)**
3.  The trait is all or partially under genetic
control.
** myopia in humans!
New behaviors under genetic control can spread very
quickly, even if the increase in fitness is small!
Group hunting in African wild dogs (Lycaon pictus).
Generation time ≈ 5 years.
10% advantage  100% of population has
behavioral trait in 500 years.
In the Pacific NW, Different
populations of garter snakes (same
species) vary in their food
preference:
slugs good OR slugs no good
A genetic /innate preference:
hybrids are intermediate.
If a snake in the coastal population showed up with
a mutated allele that changed its olfactory
preference such that slug = good, given the
abundance of slugs near the coast, that snake would
have much more food available, and leave more
genes in the next generation.
If the reproductive success of the individuals with
that allele was just 1% more than “normal” snakes,
in 10,000 years the coastal population would be
composed almost entirely of slugs-are-OK snakes.
BUT…
Is there one best trait among variants?
Often multiple selection pressures will lead
to two or more stable phenotypes, each
an equally successful behavioral strategy.
(more on this later)
This begs the question:
How much of a behavior is under
genetic control?
In some cases, artificial selection
experiments can provide data (a
theoretical experiment example)…
Pop variation in
how fast a novel
object is
approached.
Only slow ones (80 seconds or slower) allowed to
breed.
Mean of original, initial population 60 seconds.
Mean of truncated breeder population 90 seconds.
Still get fast
approach
individuals
After truncated population allowed to breed, mean of
2nd generation = 70 seconds.
Note: mean shifted faster, from 90 to 70 seconds!
Artificial selection did not get rid of all of the fast
approach phenotype.
The heritability of approach speed:
Xgen2 = 70 s
Xgen1 = 60 s
Xsel = 90 s
Xgen2 – Xgen1 = 70 – 60 = 10 s
Xsel - Xgen1 = 90 – 60 = 30 s
(achieved)
(goal)
Heritability =
= 10/30 = 33%
How much of a behavior is under
genetic control?
In addition to artificial selection, one
can measure the consistency of traits
from parents to offspring (An actual
experiment) …
Some swallows aggregate in large breeding colonies,
others in small colonies. Learned? Innate? Random?
Offspring do what their
parents did:
Cross-fostered birds raised in
“opposite” colony – parental
preference persists:
Note: The way the parent-offspring relationship is
expressed is as a “correlation”.
We correlate the
X and Y
variables.
How?
A simple math/stats technique will produce a
“least-squares” linear regression line, fit to the data
values.
A correlation
coefficient reports
how well the line
represents the
trend in the data.
1 is perfect
correlation.
0 is no correlation
How much of a behavior is under
genetic control?
Sometimes there are “natural”
experiments …
Some guppies live permanently in low-predation
areas and others in high predation areas.
Waterfalls  gene flow barrier.
Physiological and behavioral differences in the populations
of guppies (Poecilia reticulata) & two other species.
Behavioral
response to
predation is
increase
school size.
Trinidad transplant experiment:
high predation
zone
1957
Arima site
guppies
No guppies
previously, no
predators.
Turure site
1990’s
Very rapid evolution (or shift in
gene frequency) to the
behavioral traits best suited to a
low predation environment.
Turure site
guppies
Kinship effects on behavior: The extreme case
of eusociality.
Social insects & NMRs
•  apparent altruistic behavior
•  Classes or caste individuals give up reproduction
Haplo-diploid system or
inbreeding  high sibling
relatedness.
Sociobiology: Conceptual breakthrough by Dawkins (The
Selfish Gene) & E.O. Wilson, 1970’s.
Social behaviors driven by degree of relatedness. Natural
selection works on the individual to increase inclusive
(direct + indirect) fitness.
But…
Not the last word, and much social progressive pressure
not to accept.
Do related species exhibit the same
behaviors?
If much or all of some behaviors are under
genetic control, and related species have
many genes in common, you would expect
this.
Behavioral phylogeny!