After maintaining our simulation pool for about two years, we find
that the composition of the population has changed considerably. Not only have guppy
numbers more than doubled under the relatively low level of predation, but also, after
only four guppy generations, the percentages of drab males to bright males have evened
out considerably.
Number of guppies: 227
Number of generations: 5
Number of weeks: 112
Male color types:
Brightest: 42%
Bright: 7%
Drab: 18%
Drabbest: 34%
After 12 guppy generations,
the pendulum has swung heavily in favor of the brightest males, who now make up more
than 70 percent of the guppy population. Endler observed these trends in the headwater
pools where there are relatively few predators.
Number of guppies: 232
Number of generations: 12
Number of weeks: 407
Male color types:
Brightest: 95%
Bright: 1%
Drab: 3%
Drabbest: 2%
Can you tell yet what
is happening? Or why? How about examining another simulation with a different set
of guppies and predator fish to find out?
