Final answer:
Local extinction of one species will occur due to the competitive exclusion principle when two species have overlapping niches. Resource partitioning allows for coexistence by evolving slightly different microniches, reducing direct competition and influencing evolution through natural selection.
Step-by-step explanation:
When two species with overlapping niches coexist, local extinction of one of the species will occur. To avoid direct competition and possible exclusion, resource partitioning can occur, leading to species evolving slightly different microniches. This principle is known as the competitive exclusion principle, which asserts that two species cannot indefinitely occupy the same niche in the same environment. When such competition for resources occurs, one species may become more efficient in utilizing resources, leading to the other species' local extinction.
To coexist, species may undergo character displacement, which entails the development of different traits that reduce competition. For example, birds may adapt to feed on different types of food, resulting in different bill shapes, allowing them to exploit different resources within the same habitat. Outcomes of such interspecific competition include species adapting to different aspects of the environment or feeding at different times, thus occupying different microniches and minimizing direct competition. This process is fundamental to the evolution of species through natural selection.