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Guppy ( Poecilia reticulata )

Guppy ( Poecilia reticulata ). 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

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Guppy ( Poecilia reticulata )

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  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. The Panda’s Thumb

  4. Spotted Hyena • In spotted hyenas, females are dominant to males

  5. Hyena genitalia

  6. 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

  7. 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

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