Transcript Biological Science 2/e

Evolution will
be fast when
selection is
strong and
heritability
high.
Native to Florida:
Balloon vine
Seed deep inside of fruit.
Introduced to Florida:
Golden rain tree.
Fruit not so puffy.
Number of bugs
Soapberry bugs
feeding on introduced
(flatter) fruits have
shorter mouthparts
Number of bugs
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Length of mouthparts (mm)
than those that feed
on native (puffier)
fruits.
Rain tree
Introduced
in the 1930’s.
Directional selection
has caused evolution
of shorter mouthparts
in soapberry bugs.
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Date that insect was collected
Directional selection on cliff swallows, caused by a winter storm.
Cold spells are rare and large swallows less agile.
Will selection continue to favor increase in body size?
Gall =
structure produced by plant
in response to insect secretion
(mimics plant hormone)
Insect larva develops inside
Goldenrod galls are made by
a fly; the fly can control, to
some extent, the size of the gall.
Birds like to eat the fly larva,
and they prefer large galls.
Downy Woodpecker on Goldenrod Gall by Robert Bateman
Should selection favor small galls, so the flies can escape
Predation by birds?
No, because a wasp parasite prefers small galls.
The wasp larva eats the fly larva.
EEEeeeew!
http://www.facstaff.bucknell.edu/abrahmsn/solidago/main.html
Stabilizing selection reduces variation
Wasp
parasite
# of individuals
Bird predators
Gall size
Sticklebacks -- disruptive selection on feeding morphology
(big)Benthic form eats invertebrates
on lake bottom.
(little) Limnetic form eats plankton in surface waters.
F1 progeny of these forms are bad at feeding anywhere!
Disruptive selection can lead to speciation.
Natural selection can’t explain sexual dimorphism.
Watch film clip.
http://www.bellingen.com/flyingfoxes/shop/otherspecies_main.html
Reproductive success
Bateman’s principle: Female RS typically limited by resources
Male RS typically limited by access to mates.
males
females
Number of mates
Male elephant seals fight to control territory, and
Sexual selection has two components:
Male-male competition (for access to mates)
Female choice (to obtain best mates possible)
Bright beak color demonstrates health in birds.
Carotenoids used to fight infection.
Bird on right has duller bill because carotenoids diverted
to fight infection.
Do females prefer to mate with males who have bright beaks?
(Used zebra finches for this experiment; easier to handle.
9/10 females chose the bright males.
Sexual dimorphism of body size in humans is about 10%.
Less than in our ancestors….
Humans also differ from other species in the extent to which
paternal care increases male reproductive success.
Don’t uncritically apply sexual selection theory to humans.