Question

The primrose, Primula kewensis, has 36 chromosomes that are similar in appearance to the chromosomes in two related species, \(P .\) floribunda \((2 n=18)\) and \(P .\) verticillata \((2 n=18)\) How could \(P .\) kewensis arise from these species? How would you describe \(P .\) kewensis in genetic terms?

Short answer

Answer: Primula kewensis could potentially arise from Primula floribunda and Primula verticillata through a process called allopolyploidy, where the two species hybridize and their chromosomes are doubled, resulting in a new species with a higher chromosome count than its parental species. Primula kewensis can be described in genetic terms as an allopolyploid species derived from Primula floribunda and Primula verticillata with a diploid count of 2n = 36, which could be a result of 18 chromosomes originating from each parent species and then duplicated in the hybrid offspring during speciation.

Step-by-step solution

Understand how many chromosomes are present in each species

Primula kewensis has 36 chromosomes, while both Primula floribunda and Primula verticillata have 18 chromosomes each. We need to figure out how a species with 36 chromosomes could arise from two species with 18 chromosomes each.

Determine how chromosomes could double during speciation

A possible way for this to happen is through a genetic event called allopolyploidy. Allopolyploidy occurs when two species hybridize, and their chromosomes are doubled, resulting in a new species with a higher chromosome count than its parental species. In this example, Primula kewensis could potentially be a hybrid species derived from both Primula floribunda and Primula verticillata due to an allopolyploidy event that doubled the chromosome count in the hybrid offspring.

Describe Primula kewensis in genetic terms

Primula kewensis, in genetic terms, could be described as an allopolyploid species derived from Primula floribunda and Primula verticillata. Its diploid count is 2n = 36, which could be a result of 18 chromosomes originating from each parent species, and then the chromosomes were duplicated in the hybrid offspring during speciation.

Key concepts

Chromosome doubling

Chromosome doubling is a fascinating process that can lead to the formation of new species by increasing the number of chromosomes in an organism. This process is particularly crucial in plants, where it can result from errors during cell division.
When a hybrid is formed between two species, each contributing a set of chromosomes, chromosome doubling can occur, resulting in offspring with a doubled number of chromosomes. This is often seen in a process called allopolyploidy.
Allopolyploidy happens when two different species mate and their hybrid offspring undergoes chromosome doubling. This doubling stabilizes the offspring's genetic material and allows it to reproduce.
For example, if species A has 18 chromosomes and species B also has 18, their hybrid might initially have a mix, totaling 18. However, if chromosome doubling occurs, the hybrid could have 36 chromosomes, like in the case of Primula kewensis.

• This process can lead to evolutionary adaptations.
• It is a natural mechanism of speciation.
• Chromosome doubling often results in greater genetic diversity.

Hybrid species

A hybrid species is formed when two different species interbreed, creating a new organism with a combination of traits from both parent species. This often occurs in plants and can be a powerful mechanism for evolution and adaptation.
In the formation of hybrid species, the parent species each contribute a set of chromosomes. Initially, the hybrid will have a combination of these genetic materials. However, without chromosome doubling, it might not be viable or able to reproduce.
A classic example of a hybrid species is Primula kewensis, believed to be a cross between Primula floribunda and Primula verticillata, both species with 18 chromosomes each.
The hybrid inherits these 18 chromosomes from each species, and through chromosome doubling, stabilizes with a total of 36 chromosomes.

• Hybrid species often have enhanced resilience and adaptability.
• Hybridization can sometimes lead to novel traits not found in parent species.
• Hybrid species contribute significantly to biodiversity.

Primula genus

The Primula genus is a large and diverse group of flowering plants commonly known as primroses. They are popular for their beautiful blooms and serve as a significant model for studies in genetics and botany.
Primula species are found across various environments, but they mostly thrive in cool, temperate regions. These plants are known for their ability to hybridize, which has led to the creation of new species with unique traits.
In the context of chromosome doubling and hybridization, the Primula genus offers valuable insights into allopolyploidy, as seen with Primula kewensis.
The Primula genus helps illustrate how new species can evolve through hybridization and chromosome doubling, allowing them to exploit different ecological niches and adapt to environmental changes.

• The genus exemplifies genetic diversity and adaptability.
• It is vital for understanding plant evolution and genetic studies.
• Primula plants are important in horticulture for their ornamental value.