Question

A fishless lake is colonized by a single fish species, which over a few thousand years gives rise to a large number of new species, each of which possess morphological changes associated with unique feeding adaptations. What is the most likely explanation for this pattern of speciation and which force of evolution is primarily responsible divergence and niche partitioning?

Answer 1

Darwin's Natural Selection is the most likely explanation for such speciation pattern. As Darwin proposed that new species come from pre existing species, and that all species share a common ancestor. Each species having its unique set of heritable differences from the commom ancestor,which have accumulated over a very long time period of thousands of years.

He called it 'Descent with Modification'. One of the most famous example similar to the example of FISHES in the question is Finches of Galapagos island as studied by Charles Darwin.

"Adaptive evolution" of the Fishes into many species from a single species happened due to its ability to adapt to the different feeding habits, which was supported by the genetic variability(already present in the gene pool of existing fish species) and mutation( favourable mutations), which was adapted as an inherited different trait.

If we talk about Niche partitioning, then the fishes were basically in the same lake, but there was definitely "RESOURCE PARTITIONING", almost similar to how the food style was differentiable in Darwin's finches at Galapagos island.