When the ranges of two different species meet, a stable 'hybrid zone' occupied by hybrid individuals may form. How is this possible? a. Two diverged populations are capable of mating and producing viable and fertile offspring. b. Hybrid individuals are always allopolyploid and are thus unable to mate with either of the original species. c. Hybrid individuals may have reduced fitness and thus be strongly selected against. d. One species has a selective advantage, so as hybridization continues, the other species will go extinct.

Verified step by step guidance

1. Identify the correct concept: A hybrid zone is an area where two different species meet and interbreed, producing hybrid offspring. Understanding this concept will help in choosing the correct answer.
2. Analyze option a: This option suggests that two diverged populations can mate and produce viable and fertile offspring. This is a key requirement for the formation of a stable hybrid zone, as it allows for the ongoing production of hybrid individuals.
3. Analyze option b: This option states that hybrid individuals are always allopolyploid and thus unable to mate with either of the original species. This is incorrect as not all hybrids are allopolyploid; many are capable of reproducing with one or both parent species.
4. Analyze option c: This option suggests that hybrid individuals may have reduced fitness and thus be strongly selected against. While this can occur, it does not explain the formation of a stable hybrid zone where hybrids continue to exist.
5. Analyze option d: This option suggests that one species has a selective advantage, leading to the extinction of the other species as hybridization continues. This does not support the formation of a stable hybrid zone but rather the dominance of one species over the other.

Key Concepts

Hybrid Zones

Hybrid zones are regions where two distinct species meet and interbreed, resulting in the production of hybrid individuals. These zones can occur when the ranges of two species overlap, allowing for gene flow between them. The stability of a hybrid zone depends on various factors, including the fitness of hybrids and the selective pressures acting on the parent species.

Viable and Fertile Offspring

For a hybrid zone to be stable, the hybrid individuals produced must be viable (able to survive) and fertile (capable of reproducing). This means that the genetic differences between the two parent species are not so great as to prevent successful mating and reproduction. The ability of hybrids to reproduce can lead to the establishment of a stable population of hybrids within the zone.

Natural Selection and Fitness

Natural selection plays a crucial role in determining the success of hybrid individuals. If hybrids have reduced fitness compared to their parent species, they may be selected against, leading to a decline in their population. Conversely, if hybrids possess advantageous traits that allow them to thrive in the hybrid zone, they may persist and contribute to the genetic diversity of the area.