Week Eight Flashcards
What is blood feeding?
Which species does this?
Ground cricket.
Females chew off the spur, consuming haemolymph throughout copulation
– Costly: Up to 8% of total body mass in study by Fedorka & Mousseau.
What is the significance of spermatophores?
Sperm transfer via exposed spermatophore.
- Allows female to choose to use male’s sperm, or not.
- Females often eat part or all of the spermatophore for nutrition.
What are spermatophylax?
Addition of a gelatinous bulb to the spermatophore delays female consumption of sperm-containing portion.
-Mormon cricket males may invest up to 20% of weight in each spermatophylax (another role-reversal in sexual selection)
Why is it beneficial for the spermatophore to evolve first?
Evolution of spermatophore is essential, before the eating of spermatophore evolves. -Nuptial gift is problematic for male.
- -Encourage polyandry by female for increased material.
- If he gives her nourishment but she uses it to go on and have another male’s offspring, he is a double-loser.
Why might have extreme repeated mating evolved in Ornebius aperta?
As a counter-adaptation to sexual conflict.
- Partners mate over 50 times in close succession; females mate with over 40 partners in breeding season.
- Males transfer only 200 sperm/spermatophore; females consume these rapidly
Repeated mating may have evolved to outgun female capacity to eat the spermatophore.
–Increase sperm numbers with successive spermatophores
What is cantharidin?
It is an irritant.Passed through the urinary tract it cuases urethral irritation, swelling, and priapism.
-Crushed Lytta vesicatoria beetles have long been used in medicine (stimulant and abortifacient) and as an aphrodesiac.
Why do fire-colored beetles consume cantharidin?
They eat, then store it in special head glands and some in a special organ to be ejaculated.
- Females evaluate males based upon their head gland secretions.
- Ejactulated cantharidin is incorporated directly into eggs, probably as a distasteful antipredator mechanism for juveniles.
Why do males employ territory defence as a mating strategy?
Males may use territory properties as a stationary form of nuptial gift.
- If resources are limiting and patchy, control of resources often means control of copulations.
- -Hummingbird males guard nectaries.
- -Chase away other males aggressively
- -Allow female access in exchange for copulation.
What is the Runaway hypothesis?
In Fisher’s Runaway, female preference for a trait has a genetic basis and variation.
- Male trait of choice is also genetically variable.
- Mating between such a pair passes both the enhanced trait & the preference for the trait to the offspring.
- Coinheritance of trait and pref for trait promotes non-random mating, cyclical reinforcement of the trait.
What was Anne Houde’s experiment with Guppies?
She took genetically variable populations of guppies
- Artificially-selected males for arbitrarily chosen colour traits.
- -Allowed greater breeding success to males with a colour SHE chose.
- Experiment showed that female preference for the trait changed along with the change in frequency of the male trait.
How is there a trade-off in function for wide eyes in Diopsidae?
Sexual selection appears to have driven the evolution of extremely wideset eyes.
- However, narrow eyes might have greater longevity, but lower RS.
- Intralocus sexual conflict.
What stops the Runaway?
Runaway sexual selection is expected to push a trait to the limit.
- The balance point between benefit and cost.
- Natural selection (reduced survival &c) is in opposition to the trait exaggeration.
- Trait is held at equilibrium.
- Rapid change in the environment could then lead the possessors of such giantised secondary sexual characteristics vulnerable to extinction.
What are the drawbacks to mate choice?
Time & energy spent evaluating rather than feeding.
Why would females go through mate choice?
They often do this in the absence of any direct benefits.
-Suggests that there is a genetic “indirect” benefit to be gained.
What does the Zahavis argue about extended phenotypes and the male condition?
Only a male in supreme condition could support ornaments that are so expensive to produce and maintain.
If condition is heritable, then male handicaps are ‘honest signals’ of condition.
- The Zahavis apply the Handicap Principle to a variety of social behaviors and not just sexual selection.
What was the reproductive success of pronghorn antelope over 4 years in the National Bison Range?
Skewed RS.
-30% of males accounted for about 60% of offspring over the study.
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How do female antelopes assess quality?
Running speed, agility, endurance, tactical spatial sense.
- Females repeatedly visit and assess males.
- Time and energy-consuming mate sampling.
What is the good genes hypothesis?
Animals with the best traits (antlers) have the best genes for survival.
What did Burley find with Zebra finches?
Males finches artificially ornamented with leg band jewelry have higher pairing success.
- Females that pair with them have lower rates of EPC and provide more nest care for young.
- Ornamented males reduce nest care and solicit EPCs.
What was the resulting energy investment for females mated to ornamented male finches?
-AND sex ratio of offspring?
Invest more energy and testosterone in male eggs, and bias their clutches to males.
What maternal effects did Gilbert et al. find due to male attractiveness?
Found a difference in egg mass investment between attractiveness groups and, found that all of the offspring traits measures varied with the attractiveness of the father.
What was the experiment of Gilbert et. al?
Authors manipulated male attractiveness by putting leg bands on fathers.
- Red = attractive
- Green = unattractive
Females provision eggs more when they mate with an (artificially) attractive male.
-In an earlier study, females paired with ornamented males allocated more testosterone to eggs.
What was the direct effect on offspring when females were mated to attractive fathers? (Gilbert et. al)
Chicks begged more, and grew faster (both sexes but significant for daughters only).
What did Hamilton and Zuk suggest about the costs of ornamentation?
It will be paid in immune function.
-Androgen hormones male males more susceptible to disease/parasitism.
