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.
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