This document discusses male mate choice in species where it has evolved, which is less common than female mate choice. It provides examples of species where males choose females based on traits like body size. Male mate choice is more likely to evolve when operational sex ratios are female-biased, so males must compete for limited females. The document outlines costs and benefits to both male and female mate choice and explains how sex roles can reverse in some species.

1. An Overview of Male Mate Choice:
A Reversed Sex Role
KAITLYN CLARK
APRIL 27, 2017

2. What is Mate Choice?
• Behavior patterns exhibited by
one sex that makes the member of
this sex more likely to mate with
specific members of the opposite
sex
• Differences in reproductive value
• Limitations to reproduction by
gametes

3. Why Female Mate Choice?
• Anisogamy – large size difference
between male and female gametes
• Females invest a greater amount
of energy into producing their eggs
than males invest into producing
sperm
• Female has a need to ensure that
the sperm fertilizing her eggs will
produce healthy, successful
offspring
• Energy not wasted

4. The Evolution of Male Mate Choice
• Convergently evolved
• Variance in male’s ability to
produce abundant number of
offspring
• Males choose females based
on body size
• Allocate greater amounts of
sperm to females with greater
body size than smaller
females
“Rejection” “Acceptance”

6. Cost-Benefit Ratio
Benefits to Male Mate Choice
• Choosing good genes for
offspring
• Less intrasexual competition
• Choose for maternal care of
offspring
Costs to Male Mate Choice
• Time expended choosing a
mate
• Energy expended in choosing
a mate

7. Sequential Choice
• Mate choice occurs differently depending on whether the
potential mates encounter each other simultaneously or
sequentially
• In Finches, male mate choice most evident when males
encounter females simultaneously
• Males invest large amount of resources into displays for the
female they choose
• Females vary in quality of desirable traits

8. Species Who Have Choosy Males
• Plethodon shermani (Red-
legged Salamander)
• Male plethodontid salamanders
use transdermal delivery of
pheromones on chosen females
• https://youtu.be/Fp_HzqosjMY

9. Species Who Have Choosy Males
• Male Bengalese finches use the
number of songs and the components
of their songs to choose female mates
• Put extra effort into their song when
near chosen female
• Make their songs louder, longer, or
more appealing to chosen female

10. Species Who Have Choosy Males
• Brentus anchorago (Long-
Snouted Weevil)
• Delia antiqua (Onion Fly)
• Gerris buenoi (Blue-
Winged Water Strider)
• Abedus herberli (Toe Biter)
• Large females
• Virgin or young females

12. Species Who Have Choosy Males
• Humans exhibit mutual mate choice
• Males (generally) prefer females with
bigger waists and fuller bodies
• Bodies better capable of providing for
offspring
• Large breasts

13. WHY ARE FEMALES NOT CHOOSING MALES?
Costs Female Mate Choice
• Decrease in maternal care
• Energy expended in choosing
a mate
• Potential to choose poor
sperm for eggs
Benefits of Female Mate
Choice
• Potential to choose good
sperm for eggs
• Possible increase in
paternal care
• Decrease in energy
expended competing for
male mates
• Chosen mate possibly
provides food, nuptial gifts,
and protection

14. Operational Sex Ratio
• Operational sex ratio – ratio of able
to produce females to able to produce
males in an area
• Male biased operational sex ratio –
more males than females
• Males compete for limited females
• Female biased operational sex ratio –
more females than males
• Females compete for limited
males
• Male mate choice occurs if a female
biased operational sex ratio exists in
an area

15. Sex Role
Reversal
• Change in the normal behavior
patterns that males and females
exhibit
• Charles Darwin – sex roles of
courtship and parental care =
males competing for access to
females who select among males
and provide for the offspring

16. Conclusion
• Male mate choice less common
than female mate choice
• Energy expended in gamete
production
• Cost/benefit ratios
• Sequential matings
• Operational sex ratios
• Sex role reversal
• Convergent evolution

17. Thank you