Which evolutionary force tends to increase genetic diversity within a population?

Migration is the evolutionary force that tends to increase genetic diversity within a population. This process involves the movement of individuals and their genetic material from one population to another. When new individuals enter a population through migration, they bring with them alleles that may not be present in the local gene pool. This influx of new genetic variations can enrich the genetic diversity of the receiving population, thereby providing a greater array of genetic traits. An increase in genetic diversity can bolster the population's ability to adapt to changing environmental conditions, resist diseases, and enhance overall survival.

In contrast, genetic drift usually leads to a reduction in genetic diversity, especially in small populations, because it can result in the random loss of alleles over time. Natural selection tends to favor the retention of advantageous traits, which can lead to decreased genetic diversity as certain alleles become more common while others are selected against. Artificial selection is a human-driven process that typically results in a specific set of traits being amplified, often reducing genetic diversity by favoring certain traits over others. Thus, migration is the key mechanism for enhancing genetic diversity within populations.