Question

Explain how adaptation to a new niche can drive speciation.

Answer 1

Niches involve adaptation to different conditions (environments, habitats, resources), and that this adaptation can drive speciation. For a species to be successful, it must be well adopted to it’s environment. Adaptation occurs through natural selection favouring variations that improves the species fitness, and ultimately leads to a new species. Adaptation can be strengthened by the occurrence of alleles more specialized to the different habitats or vanish if generalist alleles arise by mutations and increase in frequency. This process can be complicated as specialist alleles may be much more common and may maintain adaptation for a long time. Therefore, even in the absence of an absolute fitness trade off between habitats, adaptation may persist for a long time before vanishing. In addition, several feedback loops can help to maintain it (the reinforcement, demographic, and recombination loops). The reinforcement can occur by modifying one of the three fundamental steps in the sexual life cycle (dispersal, syngamy, meiosis), which promotes genetic clustering by causing specific genetic associations. Distinguishing these mechanisms complements the one- versus two-allele classification. In general, the relative rates of the two processes (specialization and reinforcement) dictate whether ecological speciation will occur or not.