Final answer:
The increased divergence between two similar rodent species sharing the same habitat is most likely due to character displacement. This biological principle occurs when species adapt to minimize competition for resources, leading to specialization and reduced direct competition. Character displacement, alongside natural selection, plays a key role in this adaptive process.
Step-by-step explanation:
The most likely explanation for why two similar rodent species are more different from each other when they occupy the same habitat, as opposed to living separately, is character displacement. When different species occupy the same area and have overlapping needs for resources such as food and nesting space, they often find themselves in direct competition. Considering the principles of competitive exclusion and natural selection, similar species coexisting in the same habitat must adapt to minimize competition, leading to character displacement.
An example can be seen in Darwin's finches, where different bird species that live close to each other have adapted to eat different types of food, resulting in birds with different types of bills due to adaptation of their feeding habits. When species like rodents share the same habitat, one way to reduce competition is by resource partitioning, which involves utilizing different types of food, areas of the habitat, or even feeding at different times of the day. This can result in each species developing specialized characteristics that reduce direct competition, ultimately promoting the survival of both species in the habitat, a process driven by natural selection.
Resource partitioning leads species to occupy different niches, allowing them to coexist by minimizing the direct competition for the same resources. When two similar rodent species live together and show increased differences, it suggests they have adapted uniquely to divide the resources available and thus survive and reproduce successfully in the same habitat, exemplifying character displacement.