Chromosomal polymorphism in Nucella lapillus

Area of Science:

• Marine biology
• Cytogenetics
• Evolutionary biology

Background:

• Nucella lapillus exhibits chromosomal polymorphism.
• Understanding this variation is key to evolutionary studies.

Purpose of the Study:

• To describe a technique for examining Nucella lapillus chromosomes.
• To analyze the distribution and drivers of chromosomal polymorphism in Nucella lapillus.

Main Methods:

• Examination of chromosomes in testicular material.
• Karyotyping to determine diploid chromosome numbers (2n=26 to 36).
• Analysis of chromosome arrangement polymorphism (Robertsonian).
• Distribution mapping across southern Britain.
• Correlation analysis between polymorphism frequency and environmental factors (wave force, water movement).

Main Results:

• The diploid chromosome number in Nucella lapillus ranges from 26 to 36.
• Eight pairs of metacentric chromosomes are consistently present.
• A Robertsonian polymorphism explains the variation, with acrocentric chromosomes in the 2n=36 form corresponding to metacentric chromosomes in the 2n=26 form.
• The polymorphism is prevalent in southwestern bays, with monomorphic 2n=26 populations elsewhere.
• Acrosome frequency is negatively correlated with wave force, indicating adaptation to water movement.

Conclusions:

• The described technique facilitates chromosomal analysis in Nucella lapillus.
• Robertsonian polymorphism in Nucella lapillus is influenced by environmental factors, particularly water movement.
• The distribution of chromosomal polymorphism is explained by selective pressures related to wave force and water movement, favoring higher chromosome frequency in areas with less water movement.