Similarly diverse: Stability of giant genomes of Brazilian and Chilean species of the genus Alstroemeria L. (Alstroemeriaceae), despite differences in heterochromatin

Repetitive sequences are important components of plant genomes and play key roles in genome size and structural variation, influencing species diversification and adaptation. Alstroemeria L. is a genus of monocotyledonous plants with giant genomes (1C = ~25 Gb). It is native to the Americas, and its distribution corresponds to two distinct groups: the Brazilian/Argentine Alstroemeria clade and the Chilean grade. Despite a conserved chromosome number (2n = 16) and some variation in chromosome morphology, these groups differ in their patterns of heterochromatin distribution. In this study, we characterized the repetitive DNA fraction of six Chilean species, one Argentine species, and two additional Brazilian species, and mapped the most abundant repeats along the chromosomes of representative species from each group. Our results identified LTR-Ty3/gypsy Tekay retrotransposons as the main repetitive component, representing 27.22% to 37% of the genome across all analyzed Alstroemeria species and largely accounting for genome size variation. Satellite DNA families ranged from 1.33% to 5.9% of the genome, but most families were shared between Brazilian and Chilean species. Despite the divergence of the Brazilian clade approximately 9.2 million years ago, these species remain genomically conserved. The different heterochromatin patterns are likely associated with the amplification of specific satellite DNA families, contributing to the longitudinal chromosomal differentiation observed, but within a broader context of overall genome conservation.