P1250095215ifMPW

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The observation
"Since in certain cases the males have acquired
their present structure, not from being better
fitted to survive in the struggle for existence,
but from having gained an advantage over other
males, and from having transmitted this
advantage to their male offspring alone, sexual
selection must here have come into action. It
was the importance of this distinction which led
me to designate this form of selection as Sexual
Selection."
The problem
"The development, however, of certain structures-
of the horns, for instance, in certain stags-
has been carried to a wonderful extreme and in
some cases to an extreme which, as far as the
general conditions of life are concerned, must
be slightly injurious to the male."
Kudu photo Spook Skelton
from Darwin's Descent of Man
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The solution??
"...the advantages which favoured males derive
from conquering other males in battle or
courtship, and thus leaving a numerous progeny,
are in the long run greater than those derived
from rather more perfect adaptation to their
conditions of life. We shall further see, and it
could never have been anticipated, that the power
to charm the female has sometimes been more
important than the power to conquer other males
in battle."
from Darwin's Descent of Man
Bighorn Sheep photo by William C. Gladish
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what's up with males generally fighting over
females? (rather than the reverse)
"most sperm... are little more
than DNA with with a propeller" -
Freeman Herron
drawing by Eric Deschamps
4
Is what's good for the goose always good for the
gander??
from Freeman Herron Evolutionary Analysis
(2004)
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sexual selection theory predicts......
1. ...that males should be
___________ and 2. ...that females
should be ________ IF
males reproductive success is limited by
_______________
and females reproductive success is limited by
competitive
choosy
access to females
ability to make and/or rear offspring
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mating in marine iguanas satisfies these
predictions...
from Freeman Herron Evolutionary Analysis
(2004)
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"...just ignore him, honey!"
why should females care??
1. he's got "good genes"
2. he brings me nice presents
3. I don't know... I just think he's cute...
4. I wanna have a "sexy son"
rock pigeon illustration by Julie Zickefoose
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Cape Cod fiddler crabs!!! (Uca pugnax?)
photos by J. Hodin
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A competitive male that outsignals or outfights
other males will mate with more females and thus
sire more offspring, even if his actions lead to
a reduction in each mated females reproductive
output.
from
The dark side of sexual selection by Brooks
and Jennions (1999) Trends in Ecology and
Evolution 14 336-7
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the fiddler crab Uca annulipes, from Mozambique
http//www.specola.unifi.it/mangroves/ fauna/inv/c
rabs/ocypodidae.htm
regenerated claw
unregenerated claw
http//www.anu.edu.au/BoZo/backwell3/research.htm
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When compared with males with un-regenerated
claws of the same claw size, the males with the
regenerated claws (which can be as many as 44
of the males in a given population!)
1. ...are just as scary to potential burrow
stealers 2. ...are just as as attractive to
females 3. but, in the event of a burrow
contest, lose their burrows more often 4.
Still, they end up finding burrows as quickly,
and might actually benefit from having
lighter claws, since such claws would be
easier to wave.
Patricia R.Y. Backwell, et al. (2000) Dishonest
signalling in a fiddler crab. Proc. R. Soc.
Lond. B 267, 719-724
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mudballs made by a male Uca tangeri from Europe
replacement
Oliveira RF et al. (1998) Functions of mudballing
behaviour in the European fiddler crab Uca
tangeri. Anim. Behav. 55 1299-1309
photo by pedro britto
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females make mud balls too...but not as organized
is this a spandrel ????!!??
Oliveira RF et al. (1998) Functions of mudballing
behaviour in the European fiddler crab Uca
tangeri. Anim. Behav. 55 1299-1309
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Uca pugillator
Denise S. Pope (2000) Testing function of fiddler
crab claw waving by manipulating social context.
Behav Ecol Sociobiol 47432437
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Christian Sturmbauer, Jeffrey S. Levinton and
John Christy (1996) Molecular phylogeny analysis
of fiddler crabs Test of the hypothesis of
increasing behavioral complexity in evolution.
Proc. Natl. Acad. Sci. USA 93 10855-10857.
Ocypode ceratophthalmus
http//www.specola.unifi.it/mangroves/ fauna/inv/c
rabs/ocypodidae.htm
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"...just ignore him, honey!"
why should females care??
1. he's got "good genes"
2. he brings me nice presents
3. I don't know... I just think he's cute...
4. I wanna have a "sexy son"
rock pigeon illustration by Julie Zickefoose
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is more time spent copulating better??
from Freeman Herron Evolutionary Analysis
(2004)