Lecture 21 Flashcards
When does courtship begin?
two potential conspecifics of the opposite sex are in close proximity
What are 2 main functions of courtship?
Mate assessment
Mate synchronization
Why is the range of courtship signals short?
Reduce eavesdropping by predators or mate competitors
Keep nest hidden
________ signals are particularly effective
Tactile
Directional information is well coded by visual displays. What does this mean?
Direct attention toward certain individuals.
Color patches and displays
Courtship signals are what?
lower in amplitude but higher in duty-cycle than attraction signals.
Courtship signals are derived from what?
reproductive intention movements
What are some reproductive intention movements?
Mimic nest construction
Mate provisioning
Nest material manipulation
What are the 4 main types of models of mate choice?
Direct benefits
Good genes
Runaway selection
Sensory exploitation
Describe the direct benefits model.
Males vary in a non-heritable phenotypic trait that indicates a direct benefit to the female and her offspring
Give an example of direct benefits model?
High song rates rates in birds linked to amount of resources in territory
Describe nuptial gifts?
Usually food, given to potential mates during courtship.
Given an example of nuptial gifts?
Female scorpion flies alter amount of time spent mating in direct proportion to size of nuptial gift
What do male scorpion flies do?
Developed aggressive
foraging behaviors
Will steal prey items from each other
Males will mimic receptive females to steal prey items from other males
Why are costly and conspicuous male traits the target of female choice?
Such traits indicate some aspect of male quality. Provide offspring with higher survivorship
What are indicator traits?
traits females use to make selection decisions (good genes model)
How do female pronghorn antelopes select mates?
Based on ability to protect harem. Males with largest harems are presumably more successful.
Byers tracked survivorship of offspring based on what?
Mother’s harem size.
What was the findings in the Byers study?
Offspring from ‘attractive’ males had higher survival
rates than offspring from other males
Genetic models of this process are based on
coevolution of three characteristics:
Male indicator trait
Female preference for the trait
extra one idk
Why should honest indicator traits be costly to produce?
More costly traits are harder to ‘fake’ and increase reliability
Low quality males cannot support the cost of these traits
The male trait (in the handicap model) and female preference are limited due to survivorship. Why?
Males w/o trait and its cost have higher fitness
Describe the Hamilton-Zuk hypothesis?
-Females select traits that indicate parasite resistance
-Body coloration is reliably
linked to endoparasite
infection
-Endoparasites aren’t visible but can have impact on outward expressed traits
What is major histocompatibility complex (MHC)?
set of genes that improves disease resistance
MHC is the most variable set of genes (no 2 ppl have matching MHC). Why?
Variability must be a result of preference for individuals with NON-matching MHC
Selection is based on olfactory cues
What was the study Wedekind did?
Tested human preference for MHC variability
Men wore the same shirt for two nights; women were asked to select the most ‘attractive’ shirt
What were the findings of the Wedekind Study?
Women reliably selected shirts from males with the most dissimilar MHC
What study did Milinski do?
Tested cues used by female sticklebacks to
detect MHC quality
Sticklebacks range in MHC alleles from ___ to _____.
2 to 8
Individuals with more alleles have what?
Strong disease resistance
What were the findings of the Milinski study?
Females reliably preferred males with the largest
number of MHC alleles
In runaway selection, a relationship exists between what?
alleles that code for a
male trait and female preference for that specific trait
What happens when the preference/trait association is set in motion?
The effect will become exaggerated over generations
Males will develop an amplified version of the
originally preferred trait
Females will apply stronger selection pressures for the
expressed trait
Female stalk eye flies prefer males with _______ eye stalks.
longer
What two test conditions were created in the stalk eye experiment?
Males with the longest eye stalks were allowed to breed
Males with the shortest eye stalks were allowed to breed
Females were selected randomly for the two treatments
What were the results in the long stalk eye condition?
Resulting offspring
had increasingly long eye stalks and the converse was true in the short eye-stalk condition
When females of the subsequent generation of short eye stalks were given free choice of mates, what happened?
they selected males
from their experimental condition (preference has to exist in females)
Cluttonbrock studies male-male competition in red deer. What are the findings?
Male stags compete to
maintain harems
23% of harem holders show signs of fighting injury
6% are permanently injured
Male red deer use what to help judge fighting ability?
bouts of roaring
When is roaring seen?
almost exclusively during mating season.
When do roaring rates increase?
When male competitors approach
