Register | Sign In


Understanding through Discussion


EvC Forum active members: 65 (9162 total)
3 online now:
Newest Member: popoi
Post Volume: Total: 915,817 Year: 3,074/9,624 Month: 919/1,588 Week: 102/223 Day: 13/17 Hour: 0/0


Thread  Details

Email This Thread
Newer Topic | Older Topic
  
Author Topic:   The limitations of Sexual Selection
Omnivorous
Member
Posts: 3978
From: Adirondackia
Joined: 07-21-2005
Member Rating: 7.3


Message 3 of 36 (620223)
06-14-2011 10:50 PM
Reply to: Message 1 by slevesque
06-14-2011 2:23 PM


Slevesque writes:
Because the very fact that a female prefers bright colors over dull colors is itself a trait of the female, and is therefore also subject to natural selection. Doesn't this imply that sexual selection is limited by natural selection, and therefore have explanatory power only in the complete absence of predators ?
At first blush, several things occur to me.
First, you are assuming that predators rely on the same perceptual apparatus (color vision) used by the female guppies to detect fitness in the male. Many marine predators instead use other senses: echolocation (dolphins), for example, or a bio-electrical field disturbance mechanism (sharks). Indeed, the rainbow panoply of marine life around coral reefs suggests that bright colors are not an insurmountable hazard. Also of note, many terrestrial creatures warn of their toxic character with bright colors.
Second, you posit that natural selection must limit sexual selection, but then assert sexual selection has explanatory power "only in the complete absence of predators"--you have no grounds to suggest the limiting effect of natural selection is absolute.
Finally, if there are color-targeting predators present, perhaps the brightly colored males display their fitness by surviving despite their attention-grabbing garb. The logic of sexual selection dictates that the selected trait denotes fitness, and perhaps sufficient speed and wariness to escape predators in this context is that fitness.
It's an interesting dynamic, though, and a great topic for discussion.


Dost thou think, because thou art virtuous, there shall be no more cakes and ale?
-Shakespeare
Real things always push back.
-William James

This message is a reply to:
 Message 1 by slevesque, posted 06-14-2011 2:23 PM slevesque has not replied

Replies to this message:
 Message 7 by slevesque, posted 06-15-2011 1:07 AM Omnivorous has not replied

  
Omnivorous
Member
Posts: 3978
From: Adirondackia
Joined: 07-21-2005
Member Rating: 7.3


Message 22 of 36 (620283)
06-15-2011 6:57 AM
Reply to: Message 8 by slevesque
06-15-2011 1:14 AM


Slevesque writes:
First, you are assuming that predators rely on the same perceptual apparatus (color vision) used by the female guppies to detect fitness in the male. Many marine predators instead use other senses: echolocation (dolphins), for example, or a bio-electrical field disturbance mechanism (sharks). Indeed, the rainbow panoply of marine life around coral reefs suggests that bright colors are not an insurmountable hazard. Also of note, many terrestrial creatures warn of their toxic character with bright colors.
Well of course, this assumption isn't really an assumption, it is more a given that the examples that pertain to my questions are those in which this is the case; ie that the choices of a female have an effect on the fitness of the males within a given environment.
Either you have specific knowledge that guppy predators use color vision to detect them, or you assumed so. Hard cases make bad law; flawed examples yield flawed conclusions. You can, of course, abandon the guppies as an example.
In some species, sexual selection works congruently with natural selection: bigger, stronger males who thus win head-butting contests, for example, also more effectively repel predators. If we are to examine the phenomena of sexually selected traits that increase susceptibility to predation, you first need to find some. Without those, we are at sea in abstractions, and awash in assumptions.
Finally, if there are color-targeting predators present, perhaps the brightly colored males display their fitness by surviving despite their attention-grabbing garb. The logic of sexual selection dictates that the selected trait denotes fitness, and perhaps sufficient speed and wariness to escape predators in this context is that fitness.
Of course other traits affect fitness, but it doesn't affect what I am saying here.
That's not what I'm saying. I am saying that sexually selected traits are intrinsically linked to reproductive fitness.
Even if we assume (as you have) that bright coloration increases predatory attention, we also know that sexually selected display traits denote reproductive fitness precisely because the displayer can afford them. Individuals who attempt displays they cannot afford are likely to be culled by predators or the consequences of metabolic extravagance--thus natural selection pressures "enforce" sexual selection. If there were no cost to the sexually selected display, there would be no benefit to sexual selection.


Dost thou think, because thou art virtuous, there shall be no more cakes and ale?
-Shakespeare
Real things always push back.
-William James

This message is a reply to:
 Message 8 by slevesque, posted 06-15-2011 1:14 AM slevesque has not replied

Replies to this message:
 Message 23 by caffeine, posted 06-15-2011 7:24 AM Omnivorous has replied

  
Omnivorous
Member
Posts: 3978
From: Adirondackia
Joined: 07-21-2005
Member Rating: 7.3


Message 24 of 36 (620287)
06-15-2011 7:37 AM
Reply to: Message 23 by caffeine
06-15-2011 7:24 AM


Re: Why guppies?
Thanks, caffeine. That's what I wanted to hear from Slevesque.
I know I could have searched for it myself, but it was his argument's burden.

This message is a reply to:
 Message 23 by caffeine, posted 06-15-2011 7:24 AM caffeine has not replied

  
Newer Topic | Older Topic
Jump to:


Copyright 2001-2023 by EvC Forum, All Rights Reserved

™ Version 4.2
Innovative software from Qwixotic © 2024