[Role of chromosomes in evolution: a new interpretation]

Area of Science:

• Genetics
• Evolutionary Biology
• Cytogenetics

Context:

• Eutherian mammals exhibit significant variation in haploid chromosome number (N) and chromosome arms (NF/2).
• The number of meiotic segregations (2N) and chiasmata frequency are linked to N and NF/2, influencing genetic variation.
• Chromosomal phylogeny in Primates, Carnivora, and Rodentia reveals distinct evolutionary patterns.

Purpose:

• To investigate the relationship between chromosomal characteristics (N, NF/2) and modes of mammalian evolution.
• To determine how karyotype variations influence genetic recombination and speciation mechanisms.
• To explore the prevalence of dichotomic versus populational evolution in mammals based on chromosomal data.

Summary:

• High haploid chromosome numbers (N) and chromosome arms (NF/2) in mammals lead to increased gametic combinations and higher recombination rates.
• These high recombination rates, associated with large karyotypes, appear to prevent dichotomic speciation, favoring instead populational evolution.
• Conversely, species with low N and NF/2 values show limited examples of dichotomic evolution, suggesting karyotype characteristics play a crucial role.

Impact:

• Karyotype modifications significantly impact population genetics and long-term evolutionary trajectories.
• Speciation modes in mammals are influenced by both chromosomal rearrangements and the inherent genetic mixing potential of their karyotypes.
• Understanding these cytogenetic factors provides insights into the diverse evolutionary pathways observed across mammalian taxa.