Genome size shifts: karyotype evolution in Crepis section Neglectoides (Asteraceae).

Area of Science:

• Plant evolutionary biology
• Genomics
• Cytogenetics

Background:

• Plant genome size is highly dynamic, with a general trend towards increase but also instances of reduction.
• The Asteraceae genus Crepis exhibits genome size reduction, particularly within the Mediterranean sect. Neglectoides.

Purpose of the Study:

• Investigate the mechanisms of genome size evolution and karyotype diversification in Mediterranean Crepis sect. Neglectoides.
• Clarify the evolutionary relationships and genomic differences among Crepis neglecta, Crepis cretica, and Crepis hellenica.

Main Methods:

• Fluorescence in situ hybridization (FISH) for karyotypic analysis.
• Molecular phylogenetics using nuclear markers (Actin, CHR12, CPN60B, GPCR1, XTH23).

Main Results:

• Genome size variation within Crepis sect. Neglectoides, with C. neglecta having a larger genome than C. cretica and C. hellenica.
• Phylogenetic analysis indicates C. cretica and C. hellenica are more closely related to each other than to C. neglecta.
• Karyotype similarity between C. neglecta and C. cretica, contrasting with C. hellenica.
• Genome size difference between C. neglecta and C. cretica primarily attributed to elimination of dispersed repetitive elements.
• Chromosomal reorganisation identified as a key factor in the karyotype formation of C. hellenica.

Conclusions:

• The findings support genome size contraction as a significant evolutionary process in Crepis.
• Differential elimination of repetitive elements and chromosomal rearrangements are crucial mechanisms shaping genome size and karyotype diversity within the genus.