When the biologist John Endler observed wild guppies in Trinidad in the 1970s, he was puzzled by the fact that male guppies exhibited a wide variation in physical appearance depending on which part of a stream they lived in. Male guppies in one part of a stream had many colourful spots on their sides, whereas male guppies in another location were relatively dull and showed only a few spots. Something must have been responsible for causing these variations.
Please formulate a conclusion that is supported by experiments with the virtual laboratory.
If increases, then decreases.