A mutation that erases the stridulatory apparatus from male forewings arose and rapidly spread across the T. oceanicus population on Kauai between 2001 and 2003 (Zuk et al. 2006). In fewer than 20 generations, more than 90% of males exhibited this mutation.

Which of the following factors most likely contributed to the rapid spread of this mutation?

1) Genetic mutation
2) Environmental factors
3) Predation pressure
4) Natural selection

The spread of a mutation in T. oceanicus on Kauai can be explained by evolutionary processes such as the founder effect, genetic drift, gene flow, and natural selection, similar to the case of Pitx gene expression in shallow-water sticklebacks.

Explanation:

The mutation in T. oceanicus that removed the stridulatory apparatus from male forewings and spread rapidly across the population on Kauai can be attributed to a variety of evolutionary mechanisms. These include founder effect, genetic drift, gene flow, and natural selection. For example, in the initial generations after the eruption, due to founder effect, isolation, and random inheritance (genetic drift), the population to the west of the islands contained a majority of the ruffled membrane alleles while the eastern population predominantly carried the smooth alleles. Over numerous generations, different evolutionary pressures including environmental factors, predation pressure, and natural selection have led to these mutations becoming more prevalent in some cases and disappearing in others. The absence of the Pitx gene expression in the developing pelvic fin of shallow-water sticklebacks, due to the absence (mutation) of a particular enhancer element upstream of Pitx, is another instance of how genes are influenced by natural selection.