Final answer:
Coevolution is the process by which two species influence each other's evolutionary pathway through natural selection. This typically occurs in closely connected ecological relationships, leading to traits that affect each other's survival and reproduction. It differs from vicariance, another speciation process, but both play roles in biodiversity and speciation.
Step-by-step explanation:
Coevolution occurs when two species undergo reciprocal evolutionary change through natural selection. In this process, the evolutionary pathway of one species is significantly influenced by the presence of the other species with which it has a close ecological relationship. This can be seen in predator-prey dynamics, parasite-host interactions, and mutualistic relationships, where species evolve traits that impact the survival and reproductive success of the other species.
For example, if one species gains an advantage through a favorable variation, natural selection may increase pressure on a competing species. This competing species would need to also develop an advantage to avoid being outcompeted. This dynamic is often described as "running to stay in the same place" in an evolutionary sense.
Vicariance, another evolutionary concept, refers to allopatric speciation that occurs when environmental factors cause the separation of organisms within a species into different geographical groups, leading to the evolution of new species. This is distinctly different from coevolution, which involves the interaction between species. Nonetheless, both coevolution and vicariance contribute to the natural process of speciation and the ongoing changes in biodiversity through geological time.