Petite Marianne River waterfall in northern Trinidad
Petite Marianne River waterfall in northern Trinidad. When guppies colonize sites above waterfalls, they generally enter an environment with lower carotenoid availability than the site from which they came, resulting in a lower carotenoid-drosopterin pigment ratio, and therefore redder orange spots on males.
(Credit: Greg Grether/UCLA ecology and evolutionary biology)