Guppy (Poecilia reticulata)

1
Guppy (Poecilia reticulata)
2
Rapid evolution in guppies

• When guppies coexist with large predatory fish,
  the guppies mature earlier at a smaller size,
  have more numerous, smaller offspring, have
  discrete courtship behavior and are secretive
• When guppies coexist with smaller predatory fish
  (that can only eat juvenile guppies), the guppies
  matured later and had larger offspring
• Transplanting guppies from the former population
  to a habitat without large fish resulted in
  acquisition of reproductive and behavioral traits
  of second population within 18 generations

3
(No Transcript)
4
The Pandas Thumb
5
(No Transcript)
6
(No Transcript)
7
Spotted Hyena

• In spotted hyenas, females are dominant to males

8
Hyena genitalia
9
Hyena meeting ceremony

• Hyenas form social groups but spend time foraging
  alone
• To identify each other as members of their group,
  two hyenas perform the meeting ceremony
• In the ceremony, the two hyenas stand next to
  each other, facing opposite directions
• Each raises the inner hind leg and presents an
  erect penis or clitoris for the other to take
  into its teeth
• The two hyenas sniff for 10-15 seconds to
  conclude the ceremony
• It is argued that the male-like female genitalia
  evolved for use in the meeting ceremony

10
An alternative explanation

• In spotted hyenas, testosterone and other
  androgens are found at high levels
• The penis and clitoris are sexual homologues
• The scrotum and labia majora are sexual
  homologues
• Because of high androgen levels, female spotted
  hyenas have male-like genitalia
• The male-like genitalia are thereforce
  exaptations for the meeting ceremony