Marine biologists are studying stickleback fish populations. There are two distinct variations in the sticklebacks based on phenotypes. They are found with the three spines more commonly in marine ecosystems while they are more commonly found without the three spines in freshwater ecosystems. This has been observed in many marine and freshwater ecosystems across the globe. What explains the variation seen in the image here across different aquatic ecosystems?
The variation in the presence of three spines in stickleback fish populations across different aquatic ecosystems can likely be explained by natural selection. Stickleback fish with three spines may have an advantage in marine ecosystems where there are more predators, as the three spines provide better protection against predation. In contrast, stickleback fish without three spines may have an advantage in freshwater ecosystems where there may be fewer predators, allowing them to allocate resources towards other traits that provide a competitive advantage in that environment. Over time, this natural selection has led to the divergence in phenotype seen in stickleback fish populations across different aquatic ecosystems.
