Final answer:
When hawthorn and apple flies interbreed, their hybrid offspring exhibit different behaviors in response to fruit scents, suggesting a decrease in hybrid fitness. This reduced fitness may be due to genetic incompatibilities arising from the interbreeding. Hybrids tend to be less fit than the parent populations, reinforcing the process of speciation.
Step-by-step explanation:
When two different fly populations, hawthorn flies and apple flies, interbreed, their hybrid offspring exhibit different behaviors in response to fruit scents.
Specifically, they are not attracted to the scent they were originally attracted to, making it difficult for them to find mates. This difference in behavior suggests that the hybrid offspring have lower fitness compared to the parent populations.
The concept of hybrid fitness refers to the ability of hybrid offspring to survive and reproduce in their environment. In this case, the hybrid offspring's inability to find proper mates due to their altered behavior indicates a decrease in their fitness. This reduced fitness may be due to genetic incompatibilities arising from the interbreeding of the two fly populations.
Hybrids can be either less fit, more fit, or about the same as the parent populations. In many cases, hybrids tend to be less fit. This reduced fitness often leads to a decrease in hybrid reproduction over time, encouraging further divergence between the original species and reinforcing the process of speciation.