BIOB51H3 Lecture Notes - Lecture 23: Parental Investment, Rough-Skinned Newt, Sensory System
5 Jul 2018
School
Department
Course
Professor
HYPOTHESIS #3: SEXY SONS
-In some species, we see elaborated traits in males, but find no fitness enhancing benefits
-Predictions
o1. Females choose males w/ the most elaborate trait (ornament/display)
o2. Sexy trait is heritable so sons of sexy males also have higher matting
success
othis differs from good genes, because (1) males w/ sexy trait have no
natural selection advantage, and (2) “sexy” trait is heritable
- the trait itself is preferred --> trait is heritable --> inheritance of attractiveness genes
-they have no NS advantage, but the ornament/display is heritable --> in this case:
variation in who even has these traits
But why are females choosy?
-EXMAPLE: spotted cucumber beetle
oMale stroke female w/ his antennae during copulation this is a sexy trait
oFemales are more likely to accept the spermatophore (sperm package) from
males that stroke faster (prediction #1: most elaborate trait)
-What we find: the sexy trait is heritable
(prediction #2)
oMethods: mate females w/ either fast
or slow males
oRemove the eggs form the mother’s
cage
oRear them under standard lab
conditions
ovariation among males in stroking rate
--> mated females to fast or slow
males
ocan identify genes for this trait OR
just find if this trait inherited --> reared in standard lab b/c reared in same
env. conditions (to control for the env)
-RESULTS: the sons of “sexy” fathers
(those who stroke faster) are also fast (in
terms of stroke rate) AND the sexy sons
of the sexy fasters also have a higher
mating success rate
find more resources at oneclass.com
find more resources at oneclass.com
-thus: this is a sexy trait and it is
heritable
BUT WHY IS IT SEXY?
-For the trait to be “sexy” most
females need to have this
preference
-There is basically no survival
advantage associated with this
trait why would females have a
preference for an arbitrary trait?
oSensory Bias Hypothesis: general features of the female’s sensory system may
make females responsive to certain “arbitrary” stimuli (i.e the male’s traits are not
related to their survival)
ZEBRA FINCHES
-Mother’s cover their nests
in random white feathers
to prevent predators from
seeing them so: they
are more in tune to look
for white feathers
oIf: there was a novel white ornament introduced, would
it lead to higher mating success?
oRESULTS: they show that if there was anovel white
ornament introduced, they try to mate with that ornament
considerably more than others so: have a sensory
bias towards white feathers
SEXUAL SELECTION IN NATURE
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
In some species, we see elaborated traits in males, but find no fitness enhancing benefits. Females choose males w/ the most elaborate trait (ornament/display: 2. Sexy trait is heritable (cid:0) so sons of sexy males also have higher matting success: this differs from good genes, because (1) males w/ sexy trait have no natural selection advantage, and (2) sexy trait is heritable. The trait itself is preferred --> trait is heritable --> inheritance of attractiveness genes they have no ns advantage, but the ornament/display is heritable --> in this case: variation in who even has these traits. -> mated females to fast or slow males: can identify genes for this trait or just find if this trait inherited --> reared in standard lab b/c reared in same env. conditions (to control for the env) For the trait to be sexy most females need to have this preference.
