1. Other communication mechanisms for courtship

2. Visual cues: UV light
Bees
Butterflies
Fishes
Lizards
Songbirds

3. Bees and butterflies detect UV light
Examples of UV signals emitted by certain flowers, above, and butterflies, below.
Mating preference to males with brighter UV reflecting patches.

4. Testing role of UV in sticklebacks
Important control experiment?

5. UV signals between males
This threat display indicates how strongly a male can bite another lizard. Both the size of the gape and the size of the white patch signal aggression and “intimidation factor”.

6. Proportion of non-escalated (open) and escalated (shaded) contests and (b) mean log duration (seconds; ±s.e.) of non-escalated and escalated contests for manipulated and control males.
Manipulated males initiated fights with longer ventral displays and more likelihood of escalation, probably due to misjudgment of their ability by their opponent.
Stapley J , Whiting M J Biol. Lett. 2006;2:

7. UV reflecting feathers influence mate choice in songbirds too
In 13/16 paired trials, females approached the male whose UV reflecting feathers had not been treated with sunscreen.
Evolution of a visual system tuned to UV wavelengths.

8. Signals Require a nervous system that can recognize important stimuli
Modifications to the nervous system form the basis for selection
Visual
Auditory
Touch
Taste/Smell
Motor patterns

9. How signals arise Co-option of an existing signal
Aggressive “skrraa” adapted to a courtship “skrraa”
Allow females to make choices between mates
Produce new signal for which perceptual ability already exists
Sensory exploitation
Bowerbirds

10. Sensory exploitation in water mites
Male trembling tricks the female into thinking there is prey inducing her to grab the male and release him. He then deposits his sperm and she picks it up, if she is receptive. Hungrier females are more receptive to this display, supporting but not firmly proving the notion that male trembling evolved to take advantage of a hungry female’s perceptual abilities.

11. DQ 9.6
Female lays eggs in nest, takes eggs into her mouth. Male swims by, flashes anal fin with orange spots, which the female tries to eat. Male deposits sperm, fertilizes eggs. Is this exploitation? Is the female’s fitness reduced to the male’s advantage?
Use sensory exploitation theory to explain the male’s behavior. Was the first male to use this signal taking advantage of the female? Is her fitness reduced?

12. Mate choice in guppies
Males that eat enough fruits obtain carotenoids that turn their scales orange. Orange males are more attractive to females of this guppie species. Why? Females were already sensitive/preferring of orange because they too enjoyed the rare fruit? This is supported by the orange disc expt.

13. Ornamentation-size of crest correlates with female receptivity
Use a stuffed bird with artificial crest of varying size. More displays to the largest crest. In all cases—frogs, fish, etc. the artificial features elicited stronger responses from females than the natural ones. Why would animals have the ability to respond to signals that they never see in the wild?

14. Role of ancestral signals
Perhaps animals react strongly to artificial stimuli because their ancestors displayed these types of stimuli in a biologically relevant setting
This particular species of lizard has lost the abdominal blue patch, but still responds appropriately to a conspecific male with an artificial blue patch painted on.

15. Role of novel stimuli Perhaps novelty plays a role in attraction
So the positive response is not ancestral, or even specific to the stimulus, it is a response to novelty.

16. Evolution of sexual selection traits
Occurs rapidly
Traits gained and lost, sometimes more than once
Hard to study
Many interpretations
Nutrition, health of male
General preference for body size
Head and tail “extensions” make the whole animal bigger

17. Summary: origin of signals
Exploiting: stimulating a sensory apparatus that evolved for another purpose
Proximate cause
Bias: female prefers novel form of male attribute because of greater fitness to her
Ultimate cause
Adaptive value: signals (giving and receiving) that are advantageous are maintained, while those that are disadvantageous are lost
Greater fitness may mean better able to provide for her and the offspring for example.
Garter snake mating mechanism—repel predators, males use response for copulation.