What would happen to mostly drab guppy that were placed in a stream with very few predators?

In a stream with very few predators, the drab guppies would likely undergo evolutionary changes over time. Here's what could happen:

1. Reduced Camouflage:

The drab coloration that provides camouflage against predators would become less advantageous since there are fewer threats. Over time, the guppies may evolve brighter and more colorful patterns, making them more noticeable and visually appealing.

2. Increased Sexual Selection:

With reduced predation pressure, the guppies can now focus more energy on reproduction. Males might develop more elaborate displays to attract females, leading to increased sexual selection. Brighter colors and distinct markings could become traits that females find more attractive.

3. Decreased Cryptic Behavior:

Since there are fewer predators to avoid, the drab guppies may gradually lose their cryptic behaviors, such as hiding among plants and rocks. This shift in behavior could make them more active and visible in the stream.

4. Divergence of Populations:

Different guppy populations within the stream may start to diverge in their appearance and traits. Some groups might develop more vibrant colors, while others might focus on other survival strategies, such as improved swimming ability or reproductive adaptations.

5. Ecological Interactions:

The changes in guppy coloration and behavior could affect the stream's ecosystem. For instance, brighter colors might attract different predators or impact interactions with other species in the habitat.

6. Genetic Variations:

The lack of intense predation pressure can allow for more genetic diversity to accumulate within the guppy population. This means that a broader range of traits can be expressed and may result in more variations in color patterns, body shapes, and other characteristics.

7. Founder Effect and Genetic Drift:

If the original drab guppy population is small, the founder effect and genetic drift could become more influential in shaping the genetic makeup of the evolving guppy population. Certain traits may become more common or rare due to chance events and limited genetic diversity.

8. Long-Term Evolution:

Over many generations, the drab guppies could evolve into visually striking and diverse populations, showcasing the remarkable adaptability of species when environmental pressures change.

In summary, the presence of very few predators in the stream would reduce the selective pressure for camouflage, resulting in evolutionary changes in the guppy population. The drab coloration would gradually give way to brighter colors, increased sexual selection, and a broader range of traits within the guppy community.